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.

Dry, Colder Pattern in Wake of Massive Blizzard

Well.. That was a pretty failed forecast for me. Talk about getting it wrong!

As for actual snowfall amounts, snow in NW Ohio ranged from a total of 8 inches near Toledo and into extreme Northern Ohio, with Paulding County snowfall ranging from 3 to 5 inches of snow. Allen County (Indiana) and Fort Wayne picked up a decent 4.5 to 6 inches of snow. Areas west didn't do so well due to fractured snowflakes (from the incredible winds), with most west of Fort Wayne picking up snow in the 1-3 inch range (a few isolated totals of 5 inches). In the entire area, even though there was a major dry slot by the afternoon, Lima and West-Central Ohio ended up with a good 9.5-11 inches of snow! All in all, it was still a significant winter storm for the area, given snowfall rates approaching 2 inches at times across a good portion of the area, and high winds, which produced blizzard conditions for long periods of times (the only reason a blizzard warning was not issued was because low visibilities below 1/4 of a mile did not last for more than 2 hours).

As for the upcoming pattern, expect very cold weather to continue to impact the area. Temperatures over the next few days will likely not hit 30. On Saturday, it is possible that temperatures hit 30, but its not likely due to cloud cover. Forecast models are beginning to nail down the timing of an arctic wave early next week, which will likely drop temperatures into the lower 20's and possibly upper 10's for a few days. After that, it is uncertain what will happen. The NAO is likely to go positive at the same time the PNA is going to go positive. What this will cause is a large trough over the Eastern United States, and a large ridge of high pressure over the West Coast. This will set up a dry, very cold pattern for the area, with only a weak potential for clipper systems. After that, its likely that the NAO goes negative once again, shifting the trough west back into the region. This could happen around late next week, which would bring the storm track back into the area, and a better possibility for snowfall. All in all, winter has finally arrived and it looks to stay for at least the next month!

A detailed post will be coming this afternoon, discussing the details and dynamics of the storm system, as well as what went wrong for the area. I will also be posting pictures from around the region of the snow. 

Don't forget to visit my Facebook page for the latest updates on the forecast!

Merry Christmas to Everyone!

I hope everyone who follows my blog has a Merry Christmas or a Happy Holidays!

I would like to note a few things in this brief discussion.

One.) The NWS has issued a Winter Storm Warning for parts of the area, including all of Northwest Ohio, and a few counties in Northeast Indiana. They are expecting a general 5-9 inches across the area, especially along the Route 24 corridor, and south, while areas south of a line from Hartford to Ottawa line will receive more in the range of 8-10 inches. Expect very heavy snow for several hours on Wednesday, along with strong winds which could lead to blizzard and whiteout conditions at times. Snow will accumulate rapidly, and because temperatures will be close to freezing, snow will melt and refreeze to roads, making them extremely slick.

Two.) The latest 09z RAP forecast (very short range model, impressive mesoscale model as well) is forecasting a farther west track of the surface wave, which could have huge implications on snowfall amounts in the area. I'll have another update late tonight or tomorrow morning.

Other than that, have a glorious day!

Changes to the Post-Christmas Storm Forecast.

A few changes are worth noting for the post-Christmas storm now.

It appears my original track was correct; tracking from western Tennessee into Eastern Kentucky. The SREF mean, the 12z and 18z NAM, and the GFS all reflect this. The Euro still seems to be a bit further south and east, but that appears to be due to the aggressive development of the secondary low near the coast on the model. At this point, even though models did trend slightly today (I wouldn't really call it a trend given that we've only seen one legitimate model run from each of the main models; More than likely, I wouldn't doubt a shift west tonight as a weak shortwave exits off the Northeast coast by tomorrow morning, causing height rises behind it), I think the storm's track is pretty set in stone, with a few wobbles here in there. A shift west and north in the storm would allow for the area to experience heavier snowfall rates with the possibility of sleet mixing in as far north as Lima (a 25-50 mile shift northwest that is). If it stays the same, I'll get to that in a moment with my latest map. If it trends east, expect lower snowfall totals, but higher potential for fluffier, accumulating snowfall. The fluffier snowflakes will accumulate in a shorter period of time, but since snowfall rates would be lighter, then I wouldn't expect more than 2-5 inches if the storm shifted east. At this time though, I don't think its very wise to trust the global models as they are heading into a very bad timeframe. They aren't very accurate with handling the 24-48 hour forecast periods, which is the timeframe which the storm is in now. And because the mesoscale guidance is still about 50-100 miles northwest of the main global guidance, I think its safe to call that the GFS/ECMWF/GGEM will all shift at least slightly northwest in the days before the storm.

A few other aspects worth noting is that even though Northwest Ohio and Northeast Indiana receive a significant snowstorm, the Interior Northeast will also see one. In fact, snowfall totals as high as 18 inches are expected over a large portion of New York State and Pennsylvania. If it weren't for the secondary low, these snowfall totals would not be nearly as high for the Northeast.

Now.. Here's my latest map! Explanations and details come below the map:

Now comes the full explanation.

Models continue to bring a strong Gulf low from far eastern Texas northeastward into Eastern Kentucky. This type of a track is called an Inside Runner, and is generally the most favorable for snowfall in the Upper Ohio Valley and Lower Great Lakes (where we are). It is a prime track because it draws in copious amounts of moisture from the Gulf of Mexico, has excellent access to cold air from the north, and it tracks south of the area, bringing the heaviest snowfall to us or just south of the area. This looks to happen with this storm as well. While the NWS has generally stayed conservative (4-7 inches east of I-69, which is still fairly decent for the area, most models are forecasting heavier snowfall amounts. So far, the GFS and ECMWF are both advertising the lowest snowfall amounts of 4-7 inches, in agreement with the NWS. The NAM is showing 8-10 inches, the Hi-resolution NAM is showing 8-10 inches, and the SREF is similar. So it appears that snowfall from U.S. 24 and south will be in the range of 8-11 inches or so, with lower amounts of 5-7 inches north of that. This is all dependent on the track of the low, which could shift in the next few model runs or so.

There will be several ingredients that need to be closely monitored over the next day or so to properly determine snowfall totals and placement. One of them is frontogenesis. Frontogenesis occurs when a temperature gradient becomes "tighter" or the temperature change across a given distance increases with time. Frontogenesis will initiate small mesoscale bands of heavy snowfall which will aid in snowfall amounts. These bands will not be detected easily until Wednesday morning. Another factor is synoptic scale forcing, such as q-vector convergence and mesoscale uplift from the right entrance region of a jet streak over Canada. This will also aid in the development of slantwise convection which will also be driven by frontogenetical bands by mid-afternoon Wednesday. Eventually, this will weaken, and that is also why areas north of Route 6 won't see as heavy of snow totals. Eventually, I believe that snow will become lighter by about 8 p.m. Wednesday, and tapering off by midnight.

In the case of the heavy snow banding, these bands will most likely set up from Fort Wayne to Toledo, but that is just my best guess at this time. It is too difficult to determine right now where these bands of heavier snowfall will set up, and therefore, I won't know until early Wednesday morning at the onset of precipitation. Visit my Facebook Page for further details with regards to the evolution of this potentially significant snow storm.

Here's a visual map of the snowfall totals that the High-resolution NAM is "printing" out. It brings most if not all of the area 6+ inches of snow, with higher amounts near Fort Wayne and southeast.

Post-Christmas New Map and Forecast

This is my latest map update for the upcoming storm after Christmas. As for the clipper coming Christmas Eve night into Christmas, I'm not worrying much about it, as it looks to produce some light snow, with the possibility of 1-2 inches of snow/sleet across the area. It could allow for a white Christmas, but it will all depend on the track of the weak shortwave.

This is the GEFS mean from 00z last night. It's indicating a very good potential for a significant snowstorm across most, or all of the region on Wednesday.

As for the more important storm, let me get to the details. Models are forecasting a strong shortwave trough to eject from the Rocky Mountains by Monday. A jet streak will enter the trough from the west, causing the system to rapidly to deepen. As it does so, the surface storm will gradually consolidate in Eastern Texas and Louisiana (making it prime for gathering copious amounts of moisture from the Gulf of Mexico). Here's where model differences come into play. Last night's 00z ECMWF model run was "stubborn" and kept the storm on the farther east track; one that would take the surface storm from Louisiana to far Eastern Tennessee and North Carolina, before transfering up the coast. In fact, it would be a very similar scenario to what the UKMET is showing with a coastal "hugger". Regardless, all models besides the Euro trended at least somewhat west, so its only a matter of time before it does. The GEFS ensemble members are farther west as well, which puts us in a prime position to safely assume that my farther north track on the map will verify. Now that I've discussed the "important" issues, let's get on with the details.

First of all, based on the map I made at the top of the post, I believe the most likely track of the storm will occur from Northeastern Texas, into Central Tennessee and Kentucky, and eventually tracking into far Eastern Ohio and West Virginia. That's my north track. I believe it may be just a hair south, and due to the Euro "holding" with its farther east solution, I will say that the track will be just about 50 miles south of my north track of the storm. This would mean moderate to heavy wet snow for the area on Tuesday night through Wednesday night. I expect most of the snow to fall during the day on Wednesday, but because high temperatures will likely be in the upper 20's, we won't have to worry about conditions being too warm for snow. One thing we may have to worry about, especially with the further north track of the storm, is the potential for sleet and freezing rain. Both the GFS and now the NAM are suggesting that parts of the area could see freezing rain/sleet for a short period of time Wednesday, mainly south of Route 30. Because we are still a ways out from the storm (3.5 days), models will resolve the details in coming days. In fact, right now, I would expect little or no freezing rain/sleet, especially if the track is in between the two forecast "solutions". I won't quite release snowfall totals yet, but at the current time, I would bet on a decent 5-10 inches of snow across the area; 5 inches across Southern Michigan, and 6-10 inches in most of NW Ohio and NE Indiana.

For further updates on both the Christmas Day clipper system and the potential significant winter storm, visit my facebook page at Northwest Ohio Storm Prediction Center.

Post-Christmas Storm Update

*If you just want a plain, non-technical forecast; skip to the part that says "non-technical" forecast.

Over the past few days, the model consensus for the track of this potentially significant storm has trended well east. So far east in fact, that the area would have no problem seeing an all-snow event. And several models do suggest the potential for a period of significant snowfall across the area (mainly east of Interstate 69. The heaviest snowfall will remain in Northwest Ohio and southeast).

But don't get excited yet. Several models have actually trended so far east that the area gets little more than a few snow showers, and lake effect after the storm. Some of the global models depict a storm moving from the Southeast and transfering to the East Coast instead of a low that travels into Kentucky, and then transfers to the East Coast (which would bring us decently heavy snowfall accumulations).

Depiction of the large trough in the East which will eventually redevelop the "block".

Many meteorologists (especially meteorologists from the East) would probably disagree with me on this next point, but I would like to put it on the table for now. One of the main reasons why the consensus track has trended east is because of the current trough of low pressure that is currently located along the East Coast. The trough will push northeast, and become trapped by a developing ridge over the Atlantic (NAO transitioning to its neutral or positive phase around Christmas). At the same time, instead of breaking down the block over Northeast Canada it shifts it west, into the Hudson Bay and regions farther west. Eventually, depending on how neutral or positive the NAO goes, will determine how strong of a rex block will develop. Current trends would indicate that because the PNA is still neutral to negative, that it should go at least to near neutral in coming days. I believe that the Euro is doing a better job (again, most would disagree with me) with handling a weaker rex block (actually, its not really a true rex block. A true rex block is an open wave pattern. In this case, the lows on either side of the block over Canada are closed, making it more similar to an omega block.) over Maritime Canada and the North Atlantic. This would tell me (as well as past analogues) that models will eventually shift back farther west. Not only this, but I believe that some of the models are over doing the strength of the initial clipper for Christmas Eve and Christmas Day. This would affect the eventual path of the storm as well. And because I believe that there will be a weaker rex block, the shortwave will travel slightly farther north than what models are indicating. While this would eventually help "strengthen" the rex block, it wouldn't do so as much as indicated by computer models.

00z ECMWF's forecast of the blocking pattern over Canada.

While I do not disagree with a primary low that transfers to the East Coast, I believe that recent model trends reflect "pseudo-reality". What I mean by this is that I believe the models are too weak, and too far east with the primary surface low. In situations such as this, the surface low will likely track through Kentucky, and southern Ohio, which would bring the area a good 6-12 inches of snow (mainly south of Route 6). BUT, it will primarily depend on how quickly the secondary low develops. Sometimes, models depict this happening too early, and some too slowly. Time will tell what will happen. At the current time, I would think it is possible that secondary development occurs faster, but it will depend on the strength of the shortwave over Texas, and how quickly energy can consolidate. Since the ECMWF generally has a better grip on these types of things, I can say that having one primary shortwave is definitely more probable then having a weaker initial wave, with several smaller ones as well.

Here's my storm track map:

Preliminary storm map.

This map is based upon the latest forecasts, and factoring in other "causations" as well. If the east trend continues today, I will shift the snow region farther eastward, but this is my best guess at this time. Most of the region will be in the dark blue, and depending on the track of the system, could bring us some decent snowfall amounts. I would expect a good 1-8 inches of snow in the dark blue (one on the edge, 8 closer to the pink). In the pink, I'm expecting a good 9-15 inches, with some areas getting 15-18 inches (isolated).

Forecasted Snowfall Amounts

Antwerp is in the 1-3 inch zone. This includes lake enhancement during the storm, but not lake effect snow AFTER the storm.

This is my snowfall map for Thursday's night storm. At the current time, based on the latest model data, I can see that a feature called a "deformation zone" will develop across the area as the main storm system strengthens rapidly. Due to the quick movement of the cold front, any precipitation that falls within this band will be all snow, based on the latest sounding diagrams. Right now, snow ratios look to be around 10:1 to 13:1. What this means is that 10 (or 13 inches of snow) will melt to 1 inch of liquid water. Multiplying by liquid water equivalent will get you snowfall. Since about 0.1 to about 0.5 inches of frozen precipitation will fall (due to partially wet snowflakes), it's likely that most of the area sees about 1 inch, to possibly five inches in NW Indiana and Southern Michigan. In the Fort Wayne region, if current NAM forecasts hold, a solid 1-3 inches of snow could fall Thursday night into Friday morning.

Right now, here is a quick timeline of the storm. Wednesday afternoon, thick cloud cover from the oncoming developing storm system will spread into the region. By late Wednesday night, probably around midnight, we will likely see bands of light rain move into the region. By early Thursday morning, rain will become steadier and heavier, before becoming lighter for a time Thursday late morning. By Thursday midday, a line of convective showers and POSSIBLY a thunderstorm could bring some heavier rainfall amounts. By the early and mid afternoon, a dry "slot" will move through the region as the cold front "blasts" through the region. During this time, temperatures will fall quite quickly into the middle and upper 30's. As the low begins to stall over southern Michigan (model consensus of the storm), the deformation zone, an elongated band of heavier precipitation, will try to swing into Eastern Indiana and Western Ohio. While the details aren't clear yet, the placement of this deformation zone will determine how much snow we actually will get. If the current trend of the storm going further south continues, I wouldn't doubt that snowfall amounts would be in the range of 2-4 inches across the area (especially if lake enhancement comes into play). If the deformation zone is farther north, then expect near or less than an inch of snow across the area.

After this storm moves through, a cold and stagnant air mass will dominate the weather conditions up until Christmas. A weak wave of colder air before Christmas could cause another shot at snow and/or lake effect snow Christmas Eve or Christmas Day. Either way, depending on snowfall Thursday night, and the next system, our area has a decent chance at seeing a white christmas. If we see a white christmas, it'll be the first in several years! After Christmas, both the GFS and ECMWF are continually hinting at a major storm system "bombing" out in the Southern Plains and heading northeastward. The ECMWF indicates that this would initially begin as a sleet/ice mix, before transitioning to all rain, and then to potentially heavy snow, and high winds. The GFS on the otherhand, has a much longer period of sleet and snow ahead of the storm, with only a brief transition to liquid precipitation, before a transition to heavy snowfall. Either way, a major Arctic wave is POSSIBLE just before New Year's Day. Keep watching for my posts for additional information on this post-Christmas storm. (Note: Some forecasters have said that this storm may end up as an East Coast storm system, and I do agree with them. It is possible that this ends up as an East Coast storm, which would leave the area high and dry, but with very cold weather, and heavy lake effect snow. I will continue to monitor the storm for additional information.).

Colder/Snowier Weather on the Way.

Finally, for the past three days or so, models have been extremely consistent with bringing very cold air into the United States in the several days leading up to Christmas.

In fact, BOTH of the most accurate global models show a massive Arctic wave into the United States in the 7-10 day period. What they show is an increasing tendency for long-term Arctic air masses into the region, which will eventually cause the pattern to transition from a stagnant, normal pattern, to a blustery, and very cold wintry pattern. In fact, if the GFS and ECMWF are correct, high temperatures would barely approach the 20's, and might not make it out of the teens by Sunday, December 23. The arctic wave will also feature heavy lake effect snow for areas downwind of Lake Michigan, as well as light snow for areas farther from the lakes.

If this were to happen, it would be a rather abrupt change from the recent pattern, and probably a more welcome pattern. At last! We have signs that this winter will be colder and snowier than 2011-2012!

GFS Forecast for Sunday morning, December 23.

ECMWF forecast for Sunday morning, December 23

Not Much Happening...

 Expect rather "bland" and dull weather conditions for the rest of the week, in advance of a warming trend, which will peak with highs in the lower to middle 40's this weekend, and rain. The storm system that will bringing yet another round of rain will be moving northeast from the Southern Plains, possibly bringing a backside snowstorm for Iowa, Nebraska, and Missouri. It will be quite   interesting to see the eventual track of this storm, but given the fact that models are suggesting that we head into a "split" flow pattern over the next week and a half, its not likely to bring much cold air in its wake. Even with these "bad" winter weather signs appearing, it still looks as if the weather pattern will become much colder, and possibly snowier right around the 21st of December.

As for the longer-range pattern, I have been monitoring the long range models, as well as past historical years, and the pattern looks to be cooperating quite nicely for a harsh, very cold and possibly snowy, January and February. The three main years that I am using are 1957-1958, 1976-1977, 1977-1978, and 2008-2009. 1957-1958 featured a very warm December across the area (with normal precipitation and below normal snowfall), transitioning to very cold weather in the latter half of the winter. 1976-1977 featured EXTREMELY cold conditions from December all the way into early March 1977, with extreme periods of intensely cold weather occurring periodically. Precipitation was below normal and snowfall was near to above normal. 1977-1978 featured a near to slightly below normal December across the area, with very cold weather building into the region for January and February. January 1978 became the snowiest January on record for the region, and February 1978 followed suite with cold and very snowy weather. At this point, the two best matches are 1977-1978, and 1957-1958, which both suggest a snowy, cold end to the winter, likely means that we are heading into a real winter pattern!

Next Storm Dawns In Upcoming Week

Here's the map for the potential storm early next week. It's very crude, and more details will be released either tonight or tomorrow.

An Update On the Long Range Pattern

I apologize for not posting anything since last Wednesday. I've been rather busy with this terrible cold of mine, and I haven't had much time to think, other than worry about school work.

Besides that, new data has come in that suggests that one of my options for the long range pattern was correct. In a past forecast, I stated that either the pattern change will occur during the week after Thanksgiving, or it will occur in mid-December, and now that seems to be the more likely case. As I stated in the December outlook, the first half of December looks near normal (cold shots "equalizing" the the warm periods), with only transient, short lived periods of colder, snowy weather. Well, it appears this forecast will hold as model guidance is now suggesting that the Gulf of Alaska Vortex will FINALLY shift west. Originally, when models were forecasting the "pattern change" for early December, they were suggesting that the Gulf of Alaska vortex would stay put (as well as keeping the Bering Sea omega block). I should have recognized that a "pattern change" cannot occur unless the Gulf of Alaska vortex breaks down or shifts west. At this time, it is expected that the Gulf of Alaska vortex will shift to near the Aleutian Islands around the December 10th timeframe. When that occurs, it is likely that a wave of Arctic air will rush southward into the United States, bringing the season's first period of "real" winter weather, and the possibility of our first accumulating snow.

At this time, it is not set in stone, and this date may end up being pushed back into Christmas week. Right now, the analogue years are really lining up for a "modest" first 2/3 of December, becoming quite harsh the last week, so this may be what will happen.

Have a great week!

Jet stream pattern as forecasted by the European model. It shows a large dip in the jet stream around 10 days from now, which could mean a *massive* Arctic wave into the United States.

Impending Storm Still On the Table

The latest information has come out from the 06z GFS model which indicates that a potential snowfall is possible for the area next week. At the current time, the models disagree widely on the track of the storm. In the more northerly track,

the Euro has the storm system's center moving through the region and northeast into Detroit, which would bring us initially rain, but then changing over to snow. In the southerly camp, the GFS has the storm system's center tracking through Southern Ohio (it has trended northward by quite a bit and is coming into agreement with the Euro), bringing our area initially periods of a wintry mix next Monday night and Tuesday, then causing wintry mix to change over to a moderate or at times *heavy* snowfall. That is the 06z GFS for us.

At this time, I'm not going with any model solution, and given what happened last year, I'm EXTREMELY skeptical of a snowstorm hitting the region next week. BUT, the possibility still remains that that a winter weather event remains on the table for the area.

Here is the 06z GFS snowfall forecast for next Monday and Tuesday. It is forecasting the potential of 6-12 inches of snow from Monday night through Wednesday!

DISCLAIMER: AGAIN, I DO NOT BELIEVE THAT THIS WILL HAPPEN. IT IS JUST ONE OF THE MANY POSSIBILITIES.

 

 

Impending Pattern Change on the Horizon

*IMPENDING PATTERN CHANGE ON THE HORIZON*

If you haven't heard yet, meteorologists are now looking at the possibility of an impending weather pattern change across a large portion of the United States. In fact, winter could begin impacting the United States rather quickly, especially after Thanksgiving (including shots of Arctic air).

Here's what's going to happen. Next weekend (after Black Friday), models generally agree that a strong upper level disturbance will move along the Canadian border and deepen. This will draw very cold arctic air southward as the low begins to close off. The cold Arctic air will drain southward into Iowa and Illinois on Friday and Saturday, before shifting eastward Saturday and Sunday into the Ohio Valley and East. Thermal profiles will favorable enough for the potential for a lake effect snow event along Lake Michigan, Lake Erie and Lake Ontario. The heaviest lake effect (of a few inches or so) will occur in the Eastern Great Lakes region, where the coldest air will likely reside over the Lakes. This Arctic wave will only be transient, and only a sign of things to come.

Next week, there is a general agreement between the ensembles and operational models that a more substantial and robust pattern could be taking shape. Currently, models disagree considerably on the magnitude, strength and track of this storm, which reveals the uselessness of model forecasts at this point in time. Based on the data I have seen, it's looking more and more likely that a strong Midwestern low will develop in the Central Plains, and move east-northeast into the Great Lakes. At this point, it is very difficult to determine the exact track of this low, or even if this low will occur, but what could and is the most likely to happen at this point is that the storm pulls extremely cold Arctic air southward behind the storm. This could in fact come into contact with moisture wrapping around the intense low pressure system, bringing a potential "blizzard" from Iowa, to Nebraska and Minnesota.

AT this point, it is not all that likely that this occurs, due to the model variability, BUT given the current signals, it is a possibility. Needless to say, behind this system's *massive* cold front, very cold air will settle into a very large portion of the Midwest, and East. In fact, at this point, due to several unfavorable signals, the worst of the below normal temperature anomalies will stay north in the Great Lakes and Midwest regions.

For our area, here's what's likely to happen: This weekend, a cold front will quickly pass through the region, dropping temperatures back into the mid and upper 30's and possibly colder if the Euro's forecast were to verify. This would likely spark numerous lake effect snow showers immediately downwind of Lake Michigan. This could in fact lead to a few snow flurries around the region by Saturday night. In everything though, this cold blast will not last long. In fact, it will last only a couple of days before getting pushed out of the region. After that, model uncertainty has lead to an uncertain forecast, and all I can say is that the pattern is likely to get a lot colder soon.
Again, this is not a forecast that is set in stone, only the most likely scenario.

Since we won't have to deal with this for about a week, have a great Thanksgiving! 

December 2012 Long-range Forecast

And here begins the December long-range forecast released by Northwest Ohio Storm Prediction Center!

I'm not going to go into detail about the long-range factors going into this forecast, as I well know that only true "weather geeks" really care about them. So for this, I will only make mention of the truly important factors.

Currently, the Equatorial Pacific is in the neutral ENSO phase, which us "weather geeks" like to sometimes call, "La Nada", which just references the fact that Neutral winters tend to have less affect on North American weather than do other variables. SST anomalies have been fluctuating, but have generally averaged just slightly above normal in the Equatorial Pacific. Current MJO forecasts (Madden Julian Oscillation, a weather pattern or frequency that occurs in the tropics, but can affect weather across the Pacific, as far away as the United States) suggest that in the next few weeks it will be going through phases 8,1, and 2. Phase 8 generally favors the strengthening of an El Nino, while phases 1 and 2 favor "La Nada's" and La Nina's. Another variable that I look at is the NAO, as well as the AO. The NAO stands for North Atlantic Oscillation, which is related to atmospheric pressure across the North Atlantic, and the AO stands for the Arctic Oscillation which is related to pressure anomalies across the Arctic (and including the stratospheric circulations). Both of these have been in the negative phase for nearly the ENTIRE fall. Last year, it was hard to keep the two negative. A negative AO/NAO couplet suggests a greater potential for cold weather to invade the Northern and Eastern United States, including the Midwest. Using a forecast of persistence, I can see the NAO staying near neutral or negative for the month of December (including the AO as well). Other variables related to my forecast include snow cover across Canada, the PDO index, the PNA index, solar cycle variation, etc. I will not go into detail on these.

As for the forecast, I'll start with the lower Great Lakes forecast. For the last few days of November and very beginning of December, long-range forecast models indicate that the pattern will become very "changeable", and is likely to go through a "pattern change" around the same time. In fact, it is all-together likely that this pattern change is marked by a major Arctic blast into the Great Lakes, which would usher in the first major lake effect snow event of the season. In the same time frame, both the NAO and AO are expected to go at least slightly negative, which supports the development of blocking across the North Atlantic, and thus a "stopped" and unchanging pattern. This could in fact allow arctic air intrusions to become more likely in December. At this point I do NOT believe that the December 2012 trough/ridge pattern will be very "blocked". This means that I do expect the pattern to still be rather "changing", but more likely to yield arctic air intrusions. In all, for the lower Great Lakes, expect slightly below normal temperatures, due to the Arctic air masses, but averaging in any "sustained" warm ups as well. As for precipitation, I expect near normal precipitation, as the storm track will favor Alberta Clippers into the region, but most "wet" storms will likely head south of the area. Areas downwind of the Great Lakes will likely see above normal precipitation and snowfall. For the rest of the Great Lakes and Ohio Valley, I think it will be definitely possible to see one decent snowstorm, but in light of recent events, most storm systems will likely feature a mix of ice/snow or heavy rainfall.

For the rest of the United States, expect below normal temperatures from the Northern Plains to the East Coast, with the core of the Arctic air still existing across Western Canada. An active southeastward storm track from the Northern Plains into the Ohio Valley and along the East Coast, will favor above normal precipitation in coastal cities, with near to below normal precipitation across the Southern Plains and Southwest United States. In the Great Lakes, precipitation will be near normal except for the Lake effect "belts". The Northern Plains will likely see near to above normal precipitation due to the storm track. This pattern I can see happening about two or three times during the month of December, each lasting about three or four days before a more transient trough/ridge pattern sets in, between these periods of Arctic cold. These will be the times when Midwestern storms make their way in, and a Great Lakes Cutter results, a storm that travels from the Central Plains into the Great Lakes region, bringing warmer conditions and heavy rains to the Ohio Valley and much of the East.

I will not yet release a Christmas Day forecast until December begins.

One point I would like to make and that is this: Once again, because of the fragile state of the ENSO phase especially, and the way the PDO has been trending, I can see that it is possible, that we see a storm track through the Ohio Valley, with near to above normal temperatures, but well above normal precipitation and potentially snowfall. This could in fact happen if a Western trough develops, which will eject disturbances into the Midwest region. I will keep an eye on this.

Here's the official forecast map:

 

Temperature Anomaly Forecast Map.

And here is the snow cover maps.. Comparing this year to last year:

Snow cover for November 2011

Snow cover November 2012, well above what last year saw.

European Ensemble Forecasts Support Pattern Change

Last Wednesday, Northwest Ohio Storm Prediction Center released a long range forecast, explaining that the ensembles were predicting a more transient and "potentially" stormier long range pattern. As you can see, this past week, we saw a major West Coast storm move into the Midwest, and slam the Upper Midwest with as much as four feet of snow, high winds throughout the Central Plains, and heavy rains to a widespread area. Not only that, but it brought along with it the first true Arctic blast of the season, with the lake effect snow affecting a large area of Michigan.

Global models are now expecting that this pattern be disrupted until Thanksgiving Week (next week). The disruption will occur as a major Gulf of Alaskan low becomes prevalent. It will cause the jet stream to "split", indicating that the pattern will be rather dry and inactive, with no major storms expected to hit any part of the United States until late next week. NOW, Global models as well as the ensembles are forecasting a potential pattern change at the end of Thanksgiving week (that could potentially screw up my entire winter forecast). In fact, the ensembles are forecasting that the Aleutian/Gulf of Alaskan low will begin to "dig" into the West Coast. In response, a strong elongated jet streak will begin to form across the Northern Plains, which will allow the PV (Polar Vortex) to begin shifting southward again. At the same time, ridging (North Atlantic blocking) will build into Greenland, forcing a trough to form in the East, with a flat ridge developing over the West. In fact, this could be the beginning of more widespread arctic air into the United States.

The storm that could bring these changes could either be a Midwest storm system, a Northeast coastal low, or both. In fact, both of these possibilities have been suggested by the global models. In my opinion, here is what will happen. A large storm will drop southeastward in the Midwest, drawing an Arctic air mass into the East. On the edge of the cold front, a secondary low could develop and move along the East Coast. Currently, there are too many differences to in fact make an accurate forecast of what will happen. In any case, this change will occur on Thanksgiving Day or the few days afterward.

More Details of the Winter Outlook

A preview of the winter forecast that is to be released later this week. It could get quite interesting this winter.
 

One thing I would like to mention is this: There are two VERY different scenarios (in my mind) that could play out. In one scenario, it becomes very similar to a hybrid El Nino winter, one in which a western ridge prevails over the Rocky Mountains and Western states, with a mean trough over the Central and Eastern United States. This would create a storm track across the Deep South and into the Western Atlantic, at which point some storms will travel up the coast and some will move out to sea. IF this scenario were true, then this would be the most common path of storm systems. This is already supported by what has happened this fall. What this would mean for the Midwest and Ohio Valley is a very cold and DRY winter, with a few periods of warmth as the Western ridge ejects eastward.  Areas along the Great Lakes would see above normal lake effect snowfall. Anywhere else in the Ohio Valley and Midwest would likely see a lack of precipitation and thus snowfall.

In Scenario TWO, this winter turns out similar to a La Nina winter hybrid. A strong Pacific jet stream sets up across the United States, with the development of a strong South-eastern ridge, while a cold Arctic air mass exists across the West and Western Canada. This would indicate a winter with near normal temperatures for the area (lower Great Lakes region), but above normal precipitation and near normal snowfall. Let me state this though: In this scenario, the first part of December will likely feature a split flow regime, indicating that the Lower Great Lakes and Midwest will probably be devoid of storm systems, but due to shallow arctic air masses, temperatures will likely be kept near to below normal. By very late December, the pattern transitions to a very strong Pacific jet, with a weak mean trough in the West, with a ridge of high pressure over the Northern Gulf of Mexico. This would put the storm track across the Midwest and through the North-eastern states. I believe that this has a likelihood of occurring due to the rapidly expanding snowpack across Western Canada and the Northern Plains. In that case, well below normal temperatures will prevail across the Northern Plains and the West, with near normal temperatures across our area, but with above normal precipitation. The East would feature near to above normal temperatures, but generally wetter conditions. I believe, if this scenario occurred, that this will last through mid-January or so, before transitioning to deeper Arctic pattern, in which the NAO/AO go strongly negative, and a backloaded winter would be the case for a good chunk of the East. February, in this scenario would be the best case for Nor'easters and monster snowstorms.

At this point, I really do not have much confidence in either of these. Either one may occur.

IN any case, I do believe this winter will likely be worse towards the end of the winter. At this point, its likely that once the winter turns for the worse over the area (cold arctic air), it will stay cold and dry. If Scenario two plays out (this is based off of the forecast that a Neutral ENSO will persist and could possibly become a weak La Nina by the end of the winter), then expect a warm, but possibly wet December through January, before colder weather builds into the region.

This is the less likely scenario in which a strong Pacific Jet stream works its way across North America.

The scenario in which the NAO/AO goes strongly negative during the months of January and February, leading to a back loaded winter.