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