Significant Winter Storm Potential To End the Winter Season

I'm very sorry for the lack of updates once again..

Regardless, I have some very important things to discuss in regards to the forecast. For the rest of weekend, expect numerous lake effect showers, especially tonight into Sunday as low level moisture increases. Temperatures will remain below 25, possibly reaching 28 tomorrow, with only light winds. By Monday, expect a brief warm-up, back into the 40's, with periods of heavy rain possible, but changing back over to snow during the overnight hours. Tuesday and Wednesday will feature highs back into the 20's and lower 30's, with partly cloudy skies. By Thursday, clouds will begin overspreading the region, with the chance of snow coming into the picture as well. This is the part I wanted to discuss.

Models continue to show the potential for a major Midwest storm to develop in the lee of the Rocky Mountains and move east-northeast towards the area. At this time, models continue to indicate a wide "spread" in the intensity of the storm, as well as the eventual track. A few models take the storm farther south, thus allowing for a better potential for a MAJOR snowstorm by Thursday night and Friday across the area. There are also a few models that take the storm farther north, but are weaker, and bring the area a nasty ice storm. Either way, a significant winter storm looks imminent across the area by the end of the week. But at the same time, I'm not very confident on what exactly is going to happen, as a few hundred-mile difference in track and amplitude of the upper level wave could mean the difference between a mix-event of sleet and slush, or a heavy snowstorm with totals over 8 inches. From what I've seen, it looks as if the storm would take a farther south track, especially in light of a developing block across Greenland, which would suppress the storm southward. This would make the event similar to the December 26th storm just about two months ago, except with heavier precipitation, and possibly worse road conditions due to ice and snow. This system will have plenty of precipitation along with it, as well as favorable conditions for heavy snowfall, especially north of Indianapolis. The reason I say Indianapolis is because there is too much uncertainty with this system, and it could still shift either north or south on the models.

As for the latest trends among models, the 12z GFS is indicating a further south and east displacement of the surface low after lee-side cyclogenesis in Eastern Colorado. This would seem to indicate that the storm would take a further southeast track towards the area, which is more favorable for heavy snow. Given expected snow ratios (this area averages near 14:1 snow ratios), and ample amounts of moisture, we may be looking at 3-7 inch snow event, even if the ice storm verifies (3-7 inches of snow at the onset would significant favor an ice storm anyway). If the colder solution verifies, I would expect a significant snowstorm. I will be releasing a map that shows where I think this major winter storm will set up either late today or tomorrow. 

New Long-Range Pattern likely to Return

After quite a long break from blogging, I've finally come back (I'll admit, I've been busy with several things), and I'll probably be blogging much more often. The topic of this post will be rather grim (in regards to the end of the winter, as well as the immediate long-range forecast).

First, let's have a recap of the winter so far. On December 1, 2012, the vast majority of the United States began with increasingly above normal temperatures. In fact, many areas were breaching records that had not been breached in over 30 years. Widespread 60's and even 70's came as far north as Indianapolis in the Ohio Valley. Although warmth was experienced last year, this season's warmth has been mitigated by intense cyclones, and strong cold fronts from the northwest. A strong cyclone plowed through the Upper Midwest, bringing blizzard conditions to the Upper Midwest, while bringing chilly air into the East. While it was not substantial, as some have been in the past, it was quite a reversal from the record warmth of the beginning of December. As December progressed, it became cooler and cooler (as is expected), with more frequent storm systems, and RAIN (ugh). Yet, we had an exceedingly lack of accumulating snowfall. In fact, until about December 20th or the 21st, no more than 0.1 inches of snow was recorded at both South Bend AND Fort Wayne International Airports. Even so, an abrupt (more of a gradual pattern response though) pattern change commenced after a large cyclone traversed the Great Lakes in the days leading up to Christmas, bringing heavy rain to the Ohio Valley and East (once again). The cold front swept through, bringing high winds and much-needed colder air to the region. By that time, the threat of a major storm system was on the horizon, and it was predicted that the storm would mainly impact the Interior regions of the Northeast, largely sparing the coastal areas. Over the next few days leading up to Christmas, model forecasts began a quick reversed trend west with the cyclone, which shifted the snowstorm threat to the Ohio Valley through the Interior Northeast and New England. By Christmas Day, not only had a heavy snowstorm commenced over the Southern Plains, but a deep low pressure system was causing the development of widespread heavy, and sometimes severe thunderstorms across the Deep South. By Christmas Night, the low pressure system was moving northeast bringing widespread heavy snow from Arkansas to Indiana/Ohio, icing to Kentucky and parts of Tennessee, as well as heavy rain and thunderstorms to parts of the East. Heavy snow continued to spread northward and eastward, producing a large swath of 6-12" inches of snow. December ended with very cold weather across the nation, and record snow cover as well.

January began very cold across most of the United States, with temperatures well below normal over a large area. Snow cover was also well above normal as several weak, southern stream systems spread snow across the Midwest, Ohio Valley and Northeastern States. Lake effect snow continued as well from Lake Michigan, to Lake Ontario. By early to mid January, a notable warming trend began, causing once again, record-warmth to engulf most of the Midwest and East for several days. Even this warmth did not last long, as a series of low pressure systems dragged a massive cold front into the East, not only producing heavy, flooding rainfall, but snowfall on the backside of the system. This cold blast was rather weak though, only producing a minimal lake effect response. In a few days time, a very strong cold front was dragged into the Midwest by a clipper system, which caused rapid temperature drops across a large region. Temperatures became unseasonably cold; the coldest weather of the season. High temperatures ranged from the -10's in the far Northern Midwest to the lower 10's in the lower Midwest and Ohio Valley. This generated a substantial lake effect response which lasted several days. Even so, dry air limited the amount of lake effect formation. By the end of January, temperatures began moderating before another major blast of cold air sent temperatures diving into the 10's, and high winds to a large portion of the Midwest and Great Lakes. It was during this time that several clipper systems delivered several periods of moderate snowfall to these regions.

By February, the month began rather cold for the East and Midwest. In coming days though, conditions began moderating over a large area, although this warm-up was mitigated by a deep snow pack just to the north. It was because of the pre-existing snow pack, as well as a few other conditions which lead to a monster Nor'easter to blast Southern New England with 3' to 4' of snow, winds to 90 mph, and whiteout conditions for a long period of time. This monster Nor'easter will not easily be forgotten on the minds of New Englanders, as it may turn out to be one of the top Nor'easters of all time. In fact, it landed in Boston's largest snowstorms of the city's records. The highest snow total was observed in Connecticut, with snowfall totals exceeding 40" of snow. By the middle of the month, temperatures have moderated again, and forecasters are once again very uncertain about the rest of the season. And this is the main subject of the latter half of this article.

It is looking more and more likely that the United States is impacted by a rather transient, progressive flow pattern, which will lead to near or just above normal temperatures through Friday, before a major trough dives into the Midwest and brings a shot of Arctic air (albeit not all that cold). It is possible that most of the area receives lake effect snow, as the largest lake effect event of the season possibly unfolds Friday and Saturday. By Sunday and Monday, a storm system will begin formation in the Southern Plains (possibly, but other model guidance such as the JMA and the NAVGEM-- the new version of the NOGAPS/GEM-- are suggesting a major coastal storm. While that isn't out of the question, I'm still rather skeptical of an earlier phase of the northern and southern stream waves), which could bring an icy mix of snow/freezing rain/sleet to the region. If the storm trends warmer, we could be looking at yet another rain event, but if it trends colder and further south, we may end up with a significant snowstorm. This remains to be seen, and it does bear watching for the time being. If it does occur, a large area from the Ozarks to the Ohio Valley/Great Lakes could receive over a foot of snow. At this time, the early week storm looks to be the warmer storm, and a possible, second storm could impact us by mid-week or later. As for the rest of the winter, its likely that it never does get truly cold and snowy, but rather bursts of intense winter weather, followed by tranquil periods of nearly spring-like weather, especially by the final days of February and early March. Early March looks to feature near normal temperatures, with possibly wetter than normal conditions, followed by an uptick in severe weather and warmer temperatures.

This is an image of tropical convective activity as viewed from infrared satellite imagery. As you can tell, the majority of the convective activity has shifted east of Indonesia and into Oceania. While this may seem very good for the MJO cycle to stall in Phases 1 and 2, another indicator from velocity potential and IR satellite suggests that the MJO is beginning to revamp back in the eastern Indian Ocean, causing the MJO cycle to propagate back into Phases 3-6, especially by the end of February. While these phases generally mean warmer than normal weather for the region, this time it may not due to the overwhelming presence of developing blocking, as well as a deep snow pack just to our north.

Tomorrow's Snow Event.

Current SPC mesoanalysis in the upper levels continues to indicate a slightly stronger shortwave than was originally forecasted by the mesoscale models. This could have strong implications, especially in regards to the amount of snowfall, and its duration. Generally, a stronger clipper in a NW flow pattern will generally head slightly farther south, given all other variables are constant, due to the fact that northwest flow patterns are highly conducive to mid and upper level frontogenesis. Sometimes, especially in highly mesoscale events, this can lead to a phenomena known as "foldogenesis", which is what can occur in intense cyclogenesis events. While this event is not related to any strong storm system, mesoscale areas of intense frontogenesis and folding of the tropopause could lead to precipitation banding at times, especially by the early morning tomorrow (6-10 a.m.) across the area. Also, precipitable water values are currently increasing to near 0.5 across parts of the Northern Plains, which will eventually be drawn into the system itself. If it is drawn into the clipper system, we may see higher snowfall totals than what the NAM is currently forecasting. Frankly, the mesoscale models neither handled Saturday or Today's snow events all that accurately, especially farther west, and so I would like to give lower credence to their forecasts. 

Even though conditions do seem slightly ideal for this event, there are some caveats to a much heavier snowfall than 2-5 inches across the area. One.) The presence of a strong dry air mass will likely impede much heavier or widespread snowfall from developing (unless the system ingests the 0.4 to 0.5 PW values over the Northern Plains, which is entirely possible given the fact that a stronger surface cyclone is currently noted on surface analysis across the Plains.). Two.) Lack of widespread upper level forcing will also limit coverage of snowfall (though conditions are slightly more ideal than they were for Saturday's clipper system). The main forcing mechanisms involved will be whether areas of strong low level frontogenesis and upper level frontogenesis can couple with each other, producing a strong ageostrophic circulation along the warm frontal boundary, which could in itself not only strengthen the surface storm, but also the coverage and intensity of precipitation bands. This, we are already seeing across parts of the Upper Midwest.

In other words, there is the possibility that some areas, especially north of Route 30, see isolated higher amounts over 2-4 inches due to mesoscale banding. Anywhere south of the Route 30 corridor will likely see around an inch or two of snow. The snow event will likely start around 3 or 4 a.m. tomorrow morning, possibly later due to the presence of strong low level dry air.

Train of Clippers Continue...

All right.. After a solid 1-3 inches of snow falling across the area today (of the fluffy variety), there seems to be several more light snow events on the way to the area over the next 72 hours. The first one will occur from late tonight into tomorrow across many areas. This will mainly be due to LES and a weak wave of warm-air advection. This will produce scattered snow showers tomorrow, likely accumulating up to an inch in some areas tomorrow, with heavier snow amounts in the lake effect region. By Sunday night, snow will "rev" up again with some lake enhancement, which will generally produce light totals across the region. By late Sunday night, the next clipper system will be approaching the region, bringing us a solid 2-4 inches, possibly up to 5 inches by late Monday night. This clipper system will be the most significant of this train of clippers. So, this is the one I will focus on.

Thermal profiles seem to suggest that ratios will be rather high for this event once again. The DGZ (which is the dendritic growth zone, where conditions are maximized for the most efficient snow crystal, dendrites) will be rather thick (approaching 200 mb, which is ideal for heavier snowfall), with max. omega also in this layer (upward vertical velocities look to be at least slightly stronger than today's event.). And then factoring in modest low-level WAA and moisture advection, we seem to have a decent event on our hands. The only negative factors seem to be a lack of higher moisture, as well as a stronger storm system (clippers generally are weak and very dry). But because of the positive factors, it seems to me that ratios could approach 20:1, and possible 30:1 over NW Ohio. With forecasted liquid precipitation amounts for this next event at 0.2 to 0.3 areawide, it seems that we will have a solid 2-5 inch snow event, and if things become even more favorable a 4-6 inch snow event (but that'll probably happen in the lake effect regions). Regardless, this snow event is something to be watched, especially because it is a clipper, which usually "surprise" the area with heavier snowfall. I'll keep my eye on this as well, and update you tomorrow on any changes.

Significant Icing Event Tomorrow; Heavy Rain Early Next Week

The NWS has issued a winter weather advisory for most, if not all of the forecast region. They are expecting ice totals to accumulate to near 0.1 inches. I'm expecting higher icing totals, as I believe it'll take longer for the warm air mass to begin mixing to the surface, and thus, temperatures will remain below freezing for longer, possibly until after midnight. Even when temperatures go above freezing, freezing rain will persist for several more hours due to the frozen nature of the ground. Thus, icing amounts could be as high as 0.25 inches, especially in light of the recent NAM (which indicates icing amounts of up to or over 0.3 inches, especially north of Route 24). My forecast is calling for 0.1 to 0.25 inches of ice area wide, with some sleet and snow accumulation also possible. By early Monday morning though (around 5 a.m. or so), freezing rain to change over to rain as temperatures rise into the upper 30's. Light to moderate rain showers will persist throughout the day Monday and into the night hours. Rain will continue to persist through Tuesday as another wave of low pressure develops.

Wednesday is when the forecast gets tricky, and rather inconsistent with the models. The GFS indicates that another surface wave of low pressure will develop along the frontal boundary in Eastern Oklahoma and move northeast, rapidly developing into a strong low pressure system. If this were to occur, I would expect another day of highs in the middle 50's on Wednesday. The NAM, on the otherhand indicates that the second wave of low pressure will be weak, and won't cause a secondary warm-up, but will allow the cold front to slide through with heavy rain and a few rumbles of thunder Tuesday night.

Models are more consistent on the arrival of a cold wave for Thursday and Friday. In fact, temperatures could rival that of what we saw during the past week. This time around though, it is likely that we see a more substantial wave of lake effect snow, possibly extending far inland. After that, a snow event is possible for next Saturday ahead of a strong clipper system. Other than that, have a great evening!

Light LES for the weekend/Freezing Rain-Icing Potential Sunday Night

There are a few things I'll discuss this evening with regards to this weekend's weather, and early next week:

First item on the agenda is today's event. Most of the area saw just under an inch of snow, with higher amounts east of Defiance. The storm really did "underperform". One of the major reasons for this (and something I hinted at in my blog post yesterday) is due to the fact that dry air was incredibly strong in the low and mid levels. It was so dry, in fact, that relative humidity levels in the 850 millibar layer were in between 1-10%! That is incredibly dry, and a lot to overcome for only a light snow event. In fact, I was even impressed that the area saw as much as we did see. The lower snowfall totals could have a bigger impact on the weather conditions for early next week as well.

For the weekend. expect periods of light snow showers, especially W of NW Ohio, which will allow for a bit more of an accumulation. For far Western and Northern Ohio, as well as Northeast Indiana, expect an inch or less of lake effect this weekend. Closer to the lake, expect several inches of snow.

Sunday night into Monday looks to get interesting, in regards to wintry precipitation and possible icing. At the current time, it looks like a period of icing is possible. The latest NAM even hints at the potential for several hours of sleet, freezing rain and snow. Right now, it looks like temperatures will be cold enough for a period of moderate snowfall late Sunday afternoon, which will evolve into sleet, and eventually freezing rain by early Monday morning. Snowfall accumulations will likely be near or under one inch, with little or no sleet accumulation. Freezing rain accumulations will be slightly harder to pinpoint, but if I had to make an educated guess, it looks like we have the potential to see over 0.10 inches of ice (which is fairly significant to driving, especially on colder surfaces). This could reek havoc on driving conditions early Monday morning. Farther north, especially in Southern and Central Michigan, there is the potential for a significant ice storm, with over a 0.3 inches of freezing rain accumulation possible north of the Indiana state-line. This will all likely change, but if you live in Michigan, I would pay attention for the possibility of a significant ice storm. 

As for Tuesday and Wednesday, we could be seeing very warm, spring-like conditions, with temperatures well into the 50's (GFS indicates temperatures in the 60's possible, but given the cold ground, this isn't all that likely). Periods of heavier rain and possibly thunderstorms will be likely during the same period before the cold front slides through late Wednesday, ushering much colder weather again. By late week, the area will be back in the deep freeze, with the potential for Lake effect and clippers to bring us light accumulating snow.

Light Snow Tomorrow; Ice/Warm-up Next Week

Cloud cover will overspread the area once again tonight, with light snow spreading into the region by early tomorrow morning, possibly as early as 4 a.m. Light to moderate snow will continue through the early to mid afternoon hours, with the possibility of 1-3 inches by the end of the day. After the main snow bands pass through, lake effect will develop and likely impact quite a few areas for most of Friday night and Saturday, possibly accumulating another inch.

As for tomorrow's main event, there are some discrepancies in snowfall amounts and precipitation amounts that models are forecasting. In the 12z NAM forecast, a good portion of the area will likely receive up to 0.2 inches of precipitation, and combined with 20:1 snow ratios (equating to a very fluffy snowfall) would produce up to four inches of snow across the area. The problem with this is that the 18z run is now forecasting about 0.1 to 0.15 inches of precipitation, which would translate to 2-3 inches of snowfall. For now, I would go conservative with this event, especially due to low level dry air at the onset of this event. I will stick with a conservative amount of 1-2 inches.

As for early next week a low pressure system will traverse the Plains from eastern Colorado into the Great Lakes region, dragging a strong cold front through the region as well.. This will likely bring a bout of showers and thunderstorms to the area on Tuesday and Tuesday night. As for Sunday night and Monday, the warm front will begin to pass through the area, bringing warmer air, and the potential for sleet and freezing rain. At this point, it is rather uncertain how much freezing rain and sleet will fall on the area Monday morning and afternoon, but it could be significant, especially if this system ends up drawing quite a bit of moisture from the Gulf of Mexico. If the low level air mass continues to trend colder for Sunday night, we may be in for a bit of snowfall as well before the sleet and freezing rain arrive. Regardless, we could have a rather dangerous commute on our hands Monday morning. While I am not expecting a major ice storm (although it is possible), any amount of ice will make things hazardous. More updates coming soon.

Arctic Blast to Impact the Area.

The coldest and worst Arctic outbreak of the season is set to hit by early Sunday, and continuing through at least Wednesday. In fact, this Arctic wave could be one of the coldest since January 2009 and January 1994. It will bring high temperatures down to near 10 on both Monday and Tuesday, and it will also bring lows down to near 0 for both Monday and Tuesday night. The main reason that it won't be significantly below zero is the fact that we have seen a lack of snow, and snow cover for that matter. Eventually though, it looks like we will see a return of a winter pattern after a warm-up by the end of next week. But that will be elaborated upon towards the end of the article.

The above image is from today's 12z run of the ECMWF ensembles. As you can see, 850 millibar temperatures will approach, and drop below -23 degrees Celsius across the area next week. Climatologically, temperatures at this level of below -20 usually produces very significant cold, and if model biases are accounted for, true high temperatures will likely be colder than what is suggested by models at the time, especially if we have accumulating snowfall on Saturday and Sunday night. Other than that, its likely that temperatures fall into the lower teens and upper single digits across the area both Monday and Tuesday. By Wednesday, temperatures will approach about 16 or 17, before rising into the lower 30's on Thursday. Thursday looks to get slightly interesting in regards to frozen precipitation, as the surface is likely to be below freezing, and the mid levels are likely to be near or above freezing. This could promote freezing rain and sleet with the approaching warm front. While it doesn't exactly look significant in terms of total precipitation, it could allow for some significant icing, especially if high temperatures trend cooler.

As for the long range forecast, it is rather uncertain what happens now, but I can honestly say that we may not actually have winter again this year. We are currently below normal in snowfall, well above normal in temperatures, and even below normal in regards to precipitation. BUT, there is still a significant chance that February becomes snowier than normal. This fact can especially be attested to due to the prevailing nature of the Southeast ridge. I don't believe that any significant blocking ever sets up over the North Atlantic (though it will likely be east-based when it does), which will keep the main trough axis in the Midwest. I am rather confident that this will set up a much snowier, wetter pattern, though it may continue to be near normal temperature wise.

Record Warmth Today/Heavy rainfall Tonight and Tomorrow.

Today's Forecast:

Latest RAP forecasts indicate temperatures will begin to infringe upon the 62-65 degree range by the middle of the afternoon today, especially across NW Ohio. This will only enhance convective cloud cover, which will develop by late afternoon in the vicinity of the cold front. Due to the warmer temperatures, instability, albeit very weak, could be slightly higher, allowing for greater rain and thunderstorm cover later tonight. While mid-level instability will be rather weak, and low levels still rather stable, I do expect the potential for at least an isolated embedded thunderstorm in the main precipitation shield.

The above image is that of RAP forecasted surface temperatures at around 3 or 4 p.m. today.  According to the RAP most, if not all of the area will hit at least 60 today, with the possibility of a few isolated spots reaching 62-65. As for the bottom image, that is the RAP forecasted sounding for the same timeframe. As you can see (for the avid weather enthusiasts out there), the sounding indicates little or no instability across the region. But the fact of the matter remains that this sounding is misleading about thunderstorm potential tonight and tomorrow for several reasons. One, when the onset of the precipitation begins, dynamic cooling, as well as evaporational cooling, will not only cool the mid levels, but it will also contribute to strengthening lapse rates. Take a closer look at the blue line. That blue indicates the thermal profile, after complete saturation commences purely from evaporation cooling. As you can see, there will be two primary regions of enhanced mid level instability, which will aid in the development of low-topped convective cells (thunderstorms) in the midst of the area of heavy rain. Another thing we must take into account is increased low level cold air advection, especially at 850 millibars, which will help strengthen lapse rates (enough possibly to allow for a brief period of surface based thunderstorms. But at this point, it would be extremely unlikely).

This is the 12z NAM's radar reflectivity forecast. This is for 1 a.m. tonight. As you can see, it is expecting a large area of heavy showers and thunderstorms to approach the area tonight. Now, comes the hard part. This event will be influenced strongly by mesoscale forcing, as well as forcing from the main upper level trough, cold front, and associated jet streak. Based on current forecasts, the strongest vertical velocities (how fast the air moves upward) will move into the region by the early morning hours, probably around 2 or 3 a.m. This will help to maximize rainfall rates, and possibly lead to flooding areawide. Other forcing factors include the mesoscale jet streak circulations, convective slantwise instability (especially when the cold front moves through Sunday mid-morning). If these factors can be maximized across the area (like the NAM is indicating), a good portion of the area will see 1"+, and a narrow corridor could experience rainfall amounts of 2-3 inches, especially along the Route 24 corridor.

As you can see, forecasted rainfall amounts will approach the 1-3 inch range across the area. The bottom image indicates the high amounts of moisture that will be involved in this system. This is one of the main factors in the reason for heavy precipitation tonight and tomorrow.

As for the details on the precipitation type concerns, it is still rather unresolved, but from the latest data of the NAM and RAP models, it looks as if the transition from rain to sleet/snow will occur in the early afternoon hours on Sunday. Although it won't accumulate more than a half an inch, it could lead to icy roadways.

After that, expect dry, cold conditions to remain for the rest of the week. After that, models are currently narrowing down a timeframe for a significant cold blast, which, if it were to happen, would break hundreds of records across the United States. In fact, the latest 12z GFS indicates 850 mb temperatures to drop below -30 across the area! (note: the 18z GFS and 00z GFS also showed the same thing, for the same timeframe). While I do not expect it to get that cold, it is possible that the area sees temperatures below zero at times. I'll keep you informed on this developing situation!

Warm, Rainy End to the Week; Arctic Blast to Follow Next Week.

While models have generally been consistent with a massive warm-up across the country for the past few weeks, what they have not done is consistently handled a potential Arctic wave towards the middle of next week, which could in fact signal the long-awaited "pattern change". The first part of this blog post will focus on this week's forecast, while the second part will focus on the potential wave of Arctic air next week, what models are showing, and what will likely happen.

Section One: Warm, Rainy End to the Week.

One to two weeks ago, models were showing a very prolonged, and very strong warm-up across two-thirds of the nation. Record temperatures were being "progged" in the Northeast and surrounding states. Now, it is likely that this does NOT happen. Models have trended towards a several day period of temperatures in the 40's and 50's, with Friday and Saturday reaching the maximum of the warm trend.

These are the MOS forecasts for high temperatures over coming days. As you can see, there are still clear differences that need to be ironed out in the short and medium range forecast.

This is the NAM sounding for 12z Friday morning (7 a.m.). Using the initial temperature profile analysis, and "mixing" the shallow boundary layer, I would expect temperatures to reach the middle and upper 60's. BUT, at the same time, showers and heavy thunderstorms will be moving through the area as well Friday morning, which will temper high temperatures. Even after heavy rain moves out of the area, cloud cover will keep high temperatures in the upper 50's. If we see cloud cover "thin" out by the afternoon hours, we may actually see temperatures rise into the lower 60's, but at this time it is unclear whether this will happen. In fact, current trends in the NAM suggest that precipitation will likely exit the region more slowly than previously suggested, giving even more credence to high temperatures in the middle to upper 50's.

The above image is that of the 18z NAM's radar reflectivity forecast for 7 a.m. Friday morning (basically showing where and how heavy precipitation is). As I stated earlier, the NAM has been trending slower and stronger with the wave of precipitation (with the possibility of thunderstorms at times Friday morning). The only difference then between the 12z NAM and the 18z NAM is that the 18z NAM is only bringing 0.4 to 0.6 inches of rain to the region, and the 12z NAM is forecasting 0.9 to 1.2 inches of rain for the Friday morning period. At this point, I'm not sure exactly what rainfall totals will be, but given the general trend towards a stronger upper level system, and better return flow from the Gulf of Mexico, a consensus between the 12z and 18z NAM may be warranted, giving the area in between 0.6 and 0.9 inches of rainfall. Another bias to take into consideration is the fact that the NAM tends to overdevelop thunderstorms in situations such as these, thus indicating a lower precipitation amount in reality, then what the model is forecasting. I'll keep you updated on this.

These two charts are comparing the 500 millibar vorticity forecast from 00z last night (NAM's run) to the 18z run from the NAM this afternoon. As is indicated, the NAM is trending slower, farther east, and stronger than was forecasted yesterday. This will focus stronger forcing on the area, which may in fact account for higher rainfall totals. At this point, again, we shall see what happens, but current indications suggest that we could actually get some decent heavy rainfall this Friday. 

As for Saturday night into Sunday, an approaching cold front, in tandem with a strong upper level trough could produce a few more showers, but nearly as extensive as Friday morning's rainfall.

Second section: Arctic wave and Winter Weather

In this section I will focus on the potential for an Arctic "blast" into the region by early next week (in the Monday/Tuesday timeframe). 

As you can see, the 12z GFS forecast charts show a slowly moving "strong" cold front moving past the region. Notice also how slow this cold front will be moving. Normally, slow-moving cold fronts are associated with the type of front known as an "anafront". An anafront produces widespread precipitation behind the frontal zone. If this were to occur, we should see periods of light snow as a possibility next Tuesday. But given the model inconsistency as of late, it would be really hard to make a forecast just based on this. After this timeframe, the GFS brings a very cold air mass into the region, and is very "stubborn" with keeping the Arctic air in the area. 

The above 12z ECMWF forecasts indicates a much quicker, and drier frontal passage with this cold front. Not only this, but the ECMWF is slightly colder, as well as more "progressive". As of right now, I'm not leaning towards either solution, as they both have the possibility of panning out. My main concern in this section is to elaborate on a potential wave of very cold air in the timeframe of January 15-17. If the ECMWF were to verify, there would be no back-end snowstorm, and possibly very little precipitation. 

What do the teleconnection forecasts have to say for the rest of the month? They continue to indicate a much more substantial wave of Arctic air to return to the Midwest and possibly the Eastern states after the 20-23rd. It seems as if the MJO may keep "in-check" the entire Pacific longwave pattern (which would limit North Atlantic blocking), which will delay the arrival of a truly sustained Arctic air mass.

The MJO forecasted phases are expected to move into Phases 6 and 7 during the same timeframe, which seems to be in conflict with the AO/NAO going negative during this same timeframe. Further analysis of tropical convection would also indicate that this is likely to hold, and the MJO may not head into Phase 8 as quickly as originally thought. This would validate the "pattern change" dates that I originally forecasted of the 20th-27th. I do expect that the MJO will eventually either become favorable or move into the infamous "Circle of Death". When the MJO becomes inactive, storm systems moving onto the Pacific Coast generally become more infrequent, and thus usually drier conditions out west.

As for the expected magnitude of this cold air? It is possible that it could be well below normal, breaching records in some areas of the Northern Plains, especially by the end of the month. I expect this to occur, mainly because of the well above normal snow cover across North America, as well as the well above average snow depth across Southern Canada, which will modify pre-existing air masses to become colder (regardless of strong downslope flow).

As for the longer range forecast, the latest analysis of the tropical Pacific continues to indicate more favorable conditions to the development and strengthening of a weak La Nina in coming weeks. I will continue to monitor this, as it could have a large impact on our spring/summer weather this year. Have a great afternoon and evening!

The ENSO state, MJO activity, and the Pattern Change

*If you're tired of my technical rants, head to my conclusion, which explains what I believe will happen.

Further analysis of the tropical waters indicates that it is possible that a La Nina ENSO state has a possibility of occurring by late winter/early spring. I don't believe it will have much impact on the rest of the winter, but it could have serious implications on the severe weather/hurricane season this year. While there isn't a very good correlation between enhancement of severe weather and ENSO state, there is a general trend and correlation between them. In fact, the most notable tornado/severe weather outbreaks have occurred during FIRST year La Nina's (Super outbreak of 1974, Super outbreak of 2011, etc.).. Generally, because of the suppressed, split flow pattern normally characterized by El Nino's, severe weather isn't enhanced because 1.) baroclinic zones are not nearly as pronounced (during El Nino winters, the strongest baroclinic contrasts exist off the Atlantic coast, which enhance storm system development, but during the spring, especially in warmer springs, this contrast weakens greatly.), and 2.) Wind shear is not nearly as substantial, nor is instability, as warm, moist flow off of the Gulf of Mexico is inhibited with a suppressed jet stream. The thing that I have observed though is the fact that severe weather seasons that are coming out of a Neutral/Positive ENSO state will usually be enhanced (case in point 2010, especially in April and May). I should be focusing on winter weather, but I've been increasingly interested in this subject for the past week or so, and I've decided to begin working on a spring season forecast for the United States.

As for my analysis of the ENSO state, here it is: I'm trying to pinpoint an accurate timeframe from which this pattern change will occur (without using the long range GFS), and that is one of the reasons why I'm focusing on the tropical circulation. It seems as if the MJO is becoming very active once again. OLR anomaly "couplets" have been increasing in intensity over the past two weeks. They are moving very slowly to the east (which is enhancing the region of convection in a positive feedback process. The negative OLR radiation regions is causing warmer temperatures, which causes lower pressure, stronger convergence, stronger moisture flux, and stronger convective development. Thus the intensification (weakening) of the MJO can be modulated by solar activity, shifting ocean currents, as well as synoptic scale mid-latitude systems, the ITCZ and irregular heating of landmasses and ocean surfaces). Not only this, but precipitation and convection has been increasingly rapidly in the tropics. This is in fact, extremely important to the Mid-latitude general circulation over the next few weeks. When the MJO is rather weak or non-existent, then it will have little effect on mid-latitude circulation patterns. This positive feedback process, as described previously, will generate an increasingly stronger, more robust Pacific Equatorial circulation, which will most exhibit a La Nina-like circulation over the next few weeks.

Orange/red indicates stronger than normal westerly winds and blue indicates stronger than normal easterly winds.

  What does this mean for the longwave/jet stream pattern? This will generally cause a strong increase in strength of the Pacific jet stream, leading to a wetter, warmer pattern across North America (as I have stated numerous times). The increased convection across the Equator is allowing for higher 500 millibar heights, "packing" the height gradient into a smaller region, allowing for a very strong jet stream, which helps to break down the longwave pattern. The longwave pattern will dissipate into a fast-flow, progressive pattern (hence the reason why I don't think this warm-up will be on the same degree of amplitude as last March's warmth, but that's a different story). I think the progressive pattern lasts longer than is currently modulated, giving the slowing, and increasing amplitude of the MJO circulation, as well as model tendency to build in a slower more stationary longwave pattern in the long range, even though it isn't warranted. Therefore, I'll pinpoint this shifting pattern back to a colder pattern to occur right around January 20th. That's my best guess at this time.

 What does this mean for the Ohio Valley region? Expect a ridge to begin building in the far Western Atlantic/East Coast region. This will happen in response to the PNA going negative (and as I already stated before, the MJO will be modulating this shifting longwave pattern). The GFS then breaks down the flow, while keeping it more amplified than it should be, and causes a rather progressive pattern of longwave troughs/ridges. The GFS does break down the pattern rather earlier than what I'm predicting, with cold weather arriving by the 12th of December. I disagreed with what it was forecasting because I don't foresee the MJO and teleconnections aligning until that same week, upon which there will be a 7-10 day lag before the actual effects of the wave set in. So for next week, expect temperatures gradually warming above normal. As this happens, snow melt, in combination with warmer, humid air (as well as a very stable low level atmosphere) will lead to dense fog and stratus at times. Temperatures will likely approach the 40's by mid-late next week. I expect that temperatures near 50 could be attained by next weekend into the following week. By that time, a major storm system could approach the area with heavy rain, and thunderstorms possible before a cold front slides through. I don't really expect any other major warm-ups though, after the 15th. After the 15th, everything will be in a transition period. While it will not be below normal, it won't be significantly above normal either. In this case, temperatures will likely fluctuate around normal, until colder weather builds in the period between 20-27th. After the 27th, it is highly likely that a highly meriodional, blocked longwave pattern will set-up, allowing nearly ideal conditions for very cold and snowy weather across the East. More updates on this in the following days.

Using the CPC MJO composite charts, and comparing them to the actual MJO phases, it seems as if the MJO phases would support warmth, but also very wet conditions across the Midwest for the next two weeks.

The top image indicates an extremely high "confidence percentage" between most of the U.S. seeing warmth during MJO phases 4-6. MJO phases are the phases that can favor moderate intensification of cool SST anomalies across the Equatorial Pacific if other factors do as well (especially a -PDO and low solar activity). Therefore, it also looks to get rather wet in coming weeks across the Midwest. The Pacific jet will likely become active as well, even when the Southeast ridge becomes suppressed, keeping the storm systems moving into the Midwest. The bottom image indicates the GEFS mean and the GFS forecast for the MJO phases. Both forecast the MJO to remain increasingly active. The GEFS, it seems, wants to break down the MJO activity well before the GFS does, and sends it back into what is known as the "Circle of Death", which usually refers to the fact that a weak MJO usually won't favor any kind of atmospheric patterns. In this case, I tend to not go with either in the model forecasts, as just yesterday, the models were forecasting the MJO to head into phases 5-6, instead of 6-8. Hopefully, these model differences will be resolved soon so that I can more accurately pinpoint the arrival of the new pattern.

With that, here's my official long range forecast through January 27th.

Please note that when I specific above/below normal precip./temps, I am referring to the possibility, but not the actual extent of above/below precip./temps. The actual extent of the precipitation anomalies will definitely be smaller than that, but the actual extent of the temperature anomalies may be accurately depicted in my forecast images.  

As for the February forecast, that will come out either tonight or tomorrow in my preliminary late winter/early spring outlook.

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Pattern Fluctuation Until Mid-late January

I'm going to make a pyschic prediction that is 100% correct. ALL of the models will be wrong. I can guarantee it. (Now for the serious part). The models are attaching onto a trend. Water vapor, and model initialization confirms that the Pacific jet stream/longwave configuration is breaking down as we speak. An old rule of thumb states that a wave number transition (and thus a "pattern change") occurs when the Pacific jet becomes incredibly strong and "straight". The long waves flatten out, and the progressive flow pattern re-establishes itself. Determining how long it will take IS the hard part of long-range forecasting. As the Pacific flow flattens out, and becomes incredibly strong and progressive, a few key processes take place in the upper level flow pattern. It sets up a condition known as hydrodynamic instability. This states that an infinitesimal wave introduced into the flow will grow at an exponential rate. Therefore, any series of shortwaves, introduced into this region of baroclinic instability will amplify the pattern. Of course, that is idealized. Other factors will be working against this transition (for every action there is an opposite and equal reaction, etc.). Factors such as chaos, potential energy being converted into kinetic energy will eventually weaken the exponential growth of such a wave. Now.. Timing this will be key. Right now, the SOI values are jumping positive. This indicates that the pressure pattern is beginning to reverse once again. When the SOI values go positive, the Hadley cell strengthens over Indonesia, and weakens over South America and the Eastern Pacific (aka. the ITCZ is farther north over Indonesia, and farther south over the Eastern Pacific). This is all related to the MJO. The MJO will become very active in coming weeks (refer to infrared imagery of the equator).. Infrared imagery indicates large areas of strong convection near the equator. So even though blocking weakens (likely the "residual" effects of a weaker stratospheric cooling that occurred a few weeks ago), the Pacific storm train will likely ramp up again in the next 10 days (based on the 45-60 day cycle of the MJO.. It's likely that the MJO propagates back into phase 7 and 8 by mid-late month, if it remains to be active). Not only this, but the increasing convection will aid in the rising SOI values, likely strengthening an entire Hadley cell circulation which favors a La Nina event. Even so, it'll take a lot more than that to put us back into La Nina so I don't expect it to happen.

Non-technical part now: The point being is that everything is changing. MJO is becoming incredibly active (more so important than we believe in mid-latitude atmospheric circulation). Blocking is breaking down due to the wave number transition, probably induced by changing MJO activity and a weak stratospheric cooling event that occurred a few weeks ago. All in all, the pattern WILL change to a more favorable pattern for winter weather. I don't think it will happen as soon as some say. I don't think it will happen as soon as DT says or a few others. It'll take until mid-late January more than likely to set things in motion, and possibly longer in order to get a more reasonable pattern to set-up. Of course, it could happen earlier, but I don't think its all that likely at this point.

 

Winter Weather Possibilities...

Here's the RAP analysis sounding at 11z this morning (6 a.m.). It's indicating a warm layer aloft, which could impact the light winter weather event that is expected to reach the region later this afternoon and evening... Let's look into detail at this sounding.

First of all, we notice that the warm layer is not sufficiently large, and temperatures in the layer are near freezing. In this case, the layer would not be sufficient enough for precipitation to completely melt. Therefore, this would likely be a sleet/snow sounding.

Even though there is a warm layer, there are several things I would like to point out. One, is that intense evaporational cooling will cool the entire column (and subsequent warm layer) below freezing, and allowing precipitation type to remain as snow. Not only evaporational cooling, but dynamic cooling, forced by the anticyclonically curved jet streak located over Michigan, will keep thermal profiles in check. The reason why I am pointing this out is because I'm expecting warmer air to continue moving above the low level cold air mass throughout the day. At the same time, I expect that dynamic and evaporational cooling will keep any warm layers from being above freezing. When the atmosphere becomes saturated later this afternoon, the warmer layer aloft might reach temperatures above freezing, and may bear watching.

If these warmer layers should warm above freezing, while surface temperatures remain at or below freezing, some areas may see a period of moderate sleet or possibly freezing rain later this afternoon, mainly southwest of Fort Wayne. North of Fort Wayne, expect light snow, and nothing more than an inch of snow. South of Fort Wayne, 1-2 inches is possible. I would keep an eye on this though.. Because if precipitation banding is stronger than currently expected, many areas could be looking at higher snowfall totals.

Post-Christmas Storm Analysis and Overview.

I promised a few of my fellow Eastern weather forecasters that I would write a detailed overview and analysis of the storm.

There will be two parts to this article; Storm summary (extent, stats, damage, etc. longevity), analysis (dynamics, movement, development, etc.), and included within the analysis is what went wrong for the areas that were "shafted".

Storm Summary

The latest snow cover analysis from NOAA shows that yesterday's blizzard produced snow liquid equivalent precipitation of up to two inches over a widespread area from the lower Ohio Valley into the Northeast. During this storm, the average snow ratio ranged from 12:1 over Michigan and Indiana, to 9:1 in Central Ohio through Maryland, and Pennsylvania. Using these ratios, as well as real-time reports, suggests that parts of Michigan, Ohio, and Indiana had snowfall in the range of 3-10 inches, and areas from southern Indiana to Northeastern Ohio had over a foot or more. Recent reports from today show that many areas in the Northeast also saw more than a foot, and its likely that any areas downwind of the Great Lakes will see additional accumulations of 6 or more inches.

Not only did this system produce heavy snow, there was also very high winds in the regions of heavy snow. In fact, the NWS had issued blizzard warnings from Arkansas into Central Indiana and Ohio. Winds gusted to 55 mph at times, producing whiteout conditions in the heaviest bands. Some of the heavier bands of snow were producing snowfall rates of nearly 2.5 inches per hour at times in Southern Indiana! This was truly a massive blizzard for the Ohio Valley region.

(Note: For any Easterners reading this article, please notify me or provide snowfall accumulation maps for the Northeastern states as well. At the time that I wrote this article, I couldn't find many. Thank you.).


This system was not just a snow and wind "producer" but it also had a significant impact in regards to severe weather and heavy rainfall. On Christmas morning, the makings of a significant severe weather outbreak were beginning over Eastern Texas, with the development of widespread heavy showers and thunderstorms on the edge of a major surge of moisture. Eventually, a major severe weather outbreak developed farther east along the Gulf Coast, with many reports of damaging tornadoes along and ahead of the cold front. One notable tornado was a wide, wedge tornado which ripped through Mobile, Alabama late Tuesday evening.

Here's the storm reports map from the SPC. As you can see, the most significant reports were of strong tornadoes.  

(This section is not completed yet as the storm total damage and effects are still being assessed so this will be updated.).

Storm Analysis: Dynamics and Development

This part is extremely technical; Skip down to the part that says, "STOP HERE" if you do not wish to read the technical details.

This storm system was not only notable in its widespread heavy snowfall, high winds, heavy rainfall, icing, and severe weather, but also in its dynamics, and development. 

The initial shortwave that eventually developed into the storm made landfall on December 23rd, at around 7 p.m. EST. Even though it made landfall on the 23rd, it had been forecasted to develop by numerical weather guidance several days beforehand. At the time of landfall, there was still significant differences in regards to how the storm would evolve, or where the primary low would track. 

By the afternoon of Christmas Eve, a strong jet streak was entering the backside of this shortwave as it traversed across the Rocky Mountains. At this point, it was rapidly deepening, and spread in numerical guidance was still rather widespread. At this point, the NWS, as well as many other forecasters, were gaining confidence in a major snowstorm/blizzard setting up from the Southern Plains into the Ohio Valley and Northeast. Winter storm watches, warnings, and advisories were beginning to be issued. Storm Prediction Center outlooks were also issued for the potential of significant severe weather on Christmas Day..

Also notice the weak shortwave "scooting" along the Ohio Valley regions. This shortwave produced snow, ice, and rain in the Mid-Atlantic and Northeastern regions. Not only this, but it brought a new wave of colder air into the Ohio Valley, paving the way for a significant snowstorm.

The weak Arctic front caused 850 millibar temperatures to drop from around 0 degrees Celsius to -8 to -10 degrees Celsius throughout the Northern Ohio Valley.

By the morning of the 25th, a significant surface wave had developed in Texas, as the shortwave deepened rapidly. The jet streak entering the shortwave was only helping matters, and was quickly deepening the surface low. A strong Arctic high was descending into the United States, and keeping the warm front further south. It was also one of multiple reasons as to why the low pressure system tracked into the Tennessee Valley. Strong vertical motion was occurring over Texas at this point, producing widespread showers and thunderstorms.

This radar image is from the early morning hours Christmas Day, 2012. Showers and thunderstorms as well as moderate to heavy snow developed rapidly over Oklahoma, New Mexico, and Texas over the next few hours.

By 8 or 9 a.m. (EST) Christmas Day, the low was beginning to consolidate over Eastern Texas, and was beginning to move along a stalled frontal boundary. To the north of the storm, a very deep Arctic air mass was enroaching upon the storm, turning heavy rain and thunderstorms into heavy snowfall.

By 8 or 9 a.m. (EST), showers and thunderstorms were expanding, as well as the heavy snowfall regions.

By early afternoon, the strengthening shortwave was rapidly developing, and becoming increasingly negatively tilted. At this point, the surface wave was rapidly developing as well, with increasing regions of showers and thunderstorms. Strong upper level forcing was forming ahead of the shortwave, and leading to the development of a shortwave ridge ahead of the storm. Thus, began the Sutcliffe self-development process.

Strong isentropic ascent had developed ahead of the warm front by late Christmas Day, with widespread cloud cover as far north as the Indiana/Michigan border. The jet streak located over Northeast Michigan, was beginning to "couple" with the jet streak over Texas, enhancing vertical motion over the Ohio and Tennessee Valleys.

Precipitation was becoming more widespread as well with large regions of heavy snowfall over Arkansas and parts of Texas. At this current time, severe weather was developing rapidly around the Gulf coast, with numerous reports of large tornadoes.

Before I move on to the day of the event, I would also like to point out that numerical models had been slightly too far west with the placement of the surface low pressure system. But I would also like to point out that numerical guidance had placed the upper level system much farther east than it actually was, with most of the dynamics occurring west of the surface low.

Due to strong divergence aloft in the left exit and right entrance region of two potent jet streaks, in tandem with isentropic ascent, and 850 millibar frontogenesis, snow bands rapidly developed over Central Indiana, as noted by the lone banding. This in itself defied the mesoscale models, which were underdeveloping the snow shield for this storm system. Also, note the strong region of reflectivities over far SW Indiana. That region had snowfall rates approaching 2.5 inches per hour at times, combined with high winds, produced conditions of zero visibility for nearly 4 hours straight.

*STOP HERE

Here's another look at the radar imagery a few hours in the future. Note the expansion and redevelopment of heavy snow bands in the northern section of the precipitation shield.

While the heaviest bands over Central and Southern Indiana did weaken, heavier bands continued to persist over West-central Ohio, and Northeastern Indiana.

The map above is a surface map from approximately 9 a.m. (EST) on December 26, 2012. At 9 a.m., snow was beginning to fall across most of the area. By 10 a.m. (EST), heavy snowfall intensified. At this point, banding became extremely intense due to mesoscale processes, unforeseen by regional models. Strong northeasterly flow intensified, and along with the heavy snowfall, produced near whiteout conditions, especially along Route 24 and east.

As for the entire storm system, it was moving into South Central Kentucky at the time, not quite becoming a secondary low just yet, but it was getting ready to transfer, as noted on the 15z RAP PV analysis.

Heavy snow was rapidly expanding, and east as well. Cities such as Washington, D.C. and regions in the Mid-Atlantic states actually had snow that wasn't even forecast to develop! This was a major blunder for the numerical weather models.

As for the Northern Ohio/Northern Indiana region, heavy snow bands were beginning to move off to the NW and persisting, producing snowfall rates that approached 1.5 inches per hour, producing near whiteout conditions at times, and terrible road conditions.

There were three main bands as indicated on radar: One was sitting of to the west of here in Western Indiana, another was sitting right over the Route 24 corridor, and the other was in Van Wert, Adams, and Wells Counties.

Snow bands began moving off to the north. Snowfall rates were just under an inch per hour over most of the area, while areas within the main bands were seeing snowfall rates of over an inch per hour.

THIS SECTION IS HIGHLY TECHNICAL

Meanwhile, the larger storm system was beginning to occlude, focusing dynamics over Northern Indiana and Ohio, while the warm conveyer belt was being "cut off" at mid levels over the lower Great Lakes region. The second image is of the average Potential Vorticity values between the 400-200 millibar levels. It indicates how strong a storm system is. At this point, the shape of the upper level wave also indicated that secondary development was commencing over the Mid-Atlantic states (note the higher PV advection values over South and North Carolina).

Here is where things started to go wrong. The large black line indicates the position of the dry slot. The dry conveyer belt was beginning to interact with the upper level wave, and was being forced to the surface as upper level "foldogenesis" was commencing in the rapidly evolving upper level wave. This basically caused subsidence in the region that was should've been in a region of strong quasi-geostrophic ascent (showing some of the problems of the QG framework). The dry slot worked its way into the area, cutting off any decent snow banding, leaving only light snow for areas NW of the Route 24 corridor. Snow banding persisted over North Central Indiana, but weakened very rapidly as the main dynamics became focused on the secondary low.

Not only this, but the strength of the upper level wave eventually cut off the warm, moist conveyer belt as well, which reduced the supply of moisture for the snow bands over Northern Indiana and Michigan. Even though snow banding was decent over Michigan after snow began cutting off over NW Ohio, it was much weaker due to the lack of moisture.

As for areas farther east, strong warm air advection, as well as stronger CVA, and potential vorticity advection, continued to produce heavy precipitation, at times heavy snow and icing. The primary low continued to rapidly weaken as the secondary low moved northeast into the Mid-Atlantic states and offshore.

By 20z on December 26th, a full and closed secondary low had developed over North Carolina, and was beginning to move northeast. The wave became increasingly negatively tilted at all levels of the atmosphere, focusing the strongest dynamics over the Central Appalachians, Pennsylvania, and Maryland.

Strong upper level CVA, in combination with the propagating PV anomaly induced even stronger bands of precipitation over Central Pennsylvania, and eastern Ohio. Most of this convective precipitation was heavy snow, north of South Central Pennsylvania, and rain south of that line.

Strong warm air advection caused snow to change over to rain in some areas of the Mid-Atlantic, while only enhancing the snow shield over the Northeast. 850-700 millibar frontogenesis caused convective snowfall over central and Northern Pennsylvania, even causing thundersnow.

 (Note: This part is not yet complete, and will not be so for a few days. Sorry for the inconvenience.)

Conclusion

Throughout the storm's developmental and mature phase, strong upper level vorticity advection, as well as the propagation of the PV anomaly allowed for strong upward vertical motion over large areas. This allowed for the development of a strong and widespread precipitation shield as the low tracked from Eastern Texas and into the Tennessee Valley. Strong winds, heavy snow, and near whiteout conditions resulted from the Ohio Valley into the Northeast, with widespread snow accumulations over one foot in many areas.

THIS ARTICLE WILL BE UPDATED AS NEW INFORMATION COMES IN. THANK YOU FOR READING THIS.