A Southern White Christmas

But those Further North Won't Be Left Out Either

Still questions remain with regards to the storm set up for Christmas Eve and Christmas Day, as I write this post during the afternoon of Wednesday, the main piece of energy that will travel out of the Pacific and along the I-40 corridor into northern Texas, Thursday, was still off the Southern California coast and was easily visible in the water vapor imagery.

Overnight, the GFS which had been a northern outlier has bitten at the bit and gone south with the storm system for Christmas Eve and Day and then took the storm easterly and made it into a storm mainly for the Atlantic and not the East Coast. I believe the GFS over corrected itself. Now the 12z run continues a southerly track but has begun to correct itself back more to the north and to the west. I expect this trend to continue over the next several runs and I am basing this on its typical bias of too far south too far east too quickly. An interesting note, one thing that I have noticed over the past while forecasting, is the GFS has in many times shown a storm system 5 to 7 days out that was initially further north, then days 3 to 5 it moved it much further south and then as the event neared crept the storm back north and in reality what happens many times is what was shown nearly a week earlier.

What this all means is that I am not convinced yet on the far southern track the GFS is advertising just like I did not buy into the ECMWF’s idea of doing the same over the last couple of days. The ECMWF is now also creaping further north. Since the modeling data is still quite varied on the overall hadling of the system moving out of the Pacific Coast and a secondary system dropping southward through the Midwest iin the northern branch of the jet stream, my overall confidence in the full forecast is medium at best and I am still leaning towards my original thought of the storm system moving along the I-40 corridor with a surface low further south between the I-10 and the I-20 corridor. This would be about 150 miles further north than the current run of the ECMWF and that would provide a bit of a different forecast from the Mid-Mississippi Valley to the Tennessee Valley.

For this forecast suite, though, I will take a blend of the NAM/ECMWF and my thought from above.

Thursday

The storm system moving through the southwestern U.S. will be moving along the I-40 corridor into New Mexico. It is during this time the system will be developing the surface low that will assist in enhancing precipitation Christmas Eve and Day.

The upper level storm and the developing surface low will produce more abundant snow for the Rockies with showers developing into Texas. Some low to middle level warm air surging northward into the Upper Midwest in advance of the storm system will help to trigger light snow to develop from South Dakota into Iowa.

The Tennessee Valley will remain well in advance of the system and I expect the sky condition to be mostly sunny for much of the day. Some high clouds are likely to be entering into the Valley through the evening hours and continuing into the overnight.

A Sunny start with clouds increasing later in the day
Low 27 High:46 (NE 5-10)

Christmas Eve
The storm will track along the I-40 corridor through the Texas Panhandle and into Oklahoma, Christmas Eve. From the low southward will be rainfall, some heavy, into northern Texas. Can’t rule out the possibility of some thunder, too. Further north, light snow will spreading out across much of Missouri, Kansas, Iowa and Nebraska. Some moderate and at time briefly heavy snow will also be possible, south of I-70 in Kansas and along the I-44 corridor in Missouri. By late in the day the snow will sink southward into much of Oklahoma and into northwest Arkansas, too.

With the slower approach of the storm system the Tennessee Valley will actually see a partly cloudy sky for much of the day before the clouds thicken and the sky become overcast. Light rain showers will begin to arrive into northwest Alabama late in the evening hours and then overspread the Valley through early morning, Christmas Day.

Partly Cloudy with Clouds Increasing and Showers Developing Late (30%)
Low: 30 High: 52

Below are some of the snowfall forecasts from the individual models. I am providing the different images as a way to illustrate how things differ amongst the models. On Wednesday, I will put out my official first numbers for this storm system.

Christmas Day
A secondary surface low will be spinning up in the northwest Gulf of Mexico late on Christmas Eve and it will likely track along the I-10 corridor. This low may track further north over time but right now I still think the surface low will be further north than the current models are forecasting. The upper low will begin merging with the secondary piece of energy dropping out of the Midwest. This phasing of the systems will be a big deciding factor on how the whole picture pans out. The current scenario looks like one that could bring some accumulating snowfall near to the Valley for Christmas Day. In addition, based on this forecast scenario the chances for rain look brief before it should become cold enough for snow to be the predominant precipitation feature.

Cloudy with rain showers changing to Snow Showers during the early morning hours(80%), Much Colder and Windy.
Low: 30 High: 35

Sunday
Still anticipate the low to track up the East Coast, on Sunday, and bring a Nor’Easter to the I-95 corridor from Virginia northward. The ECMWF would suggest possibly even further south into the Carolinas. The Valley will remain in the cold flow with variably cloudy skies and occasional flurries fluttering about.

Variably Cloudy with a few flurries possible (20%), Blustery and Cold
Low: 25 High 35

Monday
Mostly Sunny and Cold
Low: 22 High: 35

Tuesday
Mostly Sunny
Low: 22 High: 42

Wednesday
Partly Cloudy
Low: 25 High: 48

Thursday
Mostly Cloudy, Chance For Showers
Low: 34 High: 50

Friday
Mostly Cloudy, A Shower Possible
Low: 43 High: 59

Christmas Snow Still In Store

For Many Along and North of I-40 But Questions Remain on Amounts

Still feeling confident on a significant winter weather event for much of the U.S. east of the Rockies and north of I-40; however, still several questions remain on the exact track the storm will take but my believe is one that will generally follow the I-40 corridor.

For complete details here is the forecast discussion:

Wednesday
Weak upper-level riding and compression ahead of an approaching cold front has allowed temperatures

to warm nicely even with abundant cloud cover and an occasional shower. Temperatures, Tuesday afternoon, were in the mid and upper 50s all across the Valley with Muscle Shoals reporting a 60 reading

as of 2 PM.

There is an associated surface wave along the front and it will be moving eastward over the Tennessee Valley overnight. This will keep temperatures mild all night in the Valley. As the low passes by during the

morning hours, the cold front will pass through southern-middle Tennessee and northern Alabama. The front will likely be stretching southwestward from northeast Alabama around 6 AM, Wednesday. This will allow colder air to filter into the Valley throughout the day. It will also turning breezy with winds turning to

the north.

Attention will be quickly turning to a strong pulse of energy off the Pacific coast of California. This w

ave will move into southern California by midday Wednesday and will help to deliver the already soggy

“Golden State” more rains and mountain snow.

This piece of energy will become the storm of concern for

much of the nation east of the Rockies for Christams Eve and Christmas Day.

Mostly Cloudy with a few scattered morning showers (30%). Turning colder and breezy with

temperatures slowly falling through the day.Low 55 (Midnight) High: 48 (3 PM) (North 10-15)
Thursday
The storm of concern will be moving along the I-40 corridor through the Southern Rockies, Thursday. Rain showers will be bubbling northward through the Lone Start State; with abundant rains and mountain snows in the Four Corners States. As the storm tracks eastward, it will try to punch some warmer air

northward in its advance. This will help to lift air and in turn allow for precipitation to develop. The first area to see snow with this system will be the Northern Plains into western Minnesota and Iowa. The first flakes of snow will likely begin falling by midday in South Dakota and Nebraska and streak eastward through the

afternoon and evening hours.
The Tennessee Valley will still be well in advance of the storm system, Thursday. so the day will likely start out on the clear side with abundant sunshine but clouds will quickly be on the return by afternoon.

A Sunny start with clouds increasing later in the day
Low 29 High:46 (NE 5-10)

Christmas EveThere is still questions on the exact track this storm system will take and it strength during the Christmas Eve/Day period. The storm still is not being analyzed well by upper-air soundings since it currently resides off the California coast; however, this will be changing by Wednesday’s modeling runs and overall

confidence should continue to improve.
The trend for the past day and half to two days is to keep this system further south than first indicated and to be slower, too. The models are all leaning on the track of the upper level system to be generally west to

east between the I-40 and I-20 corridors with a surface low tracking a bit further south of the upper level

support along the I-20 corridor. The strength of the storm is also varying amongst the forecasts.
The reason the models continue with a more southerly track is they are indicating a secondary strong piece of energy diving southward in the northern branch of the jet stream and this helps to push the West Coast storm system further south. The GFS is remaining the furthest north of the models but it is also the weakest while the ECMWF is the strongest and furthest south. and the middle of the road solution, and the one I am going to lean with at this time, is the CMC.
This would provide a track of the upper level storm generally along the I-40 corridor with the associated

surface low tracking along the I-20 corridor through Texas into Louisiana and then southeastward to along the Gulf Coast.

This track would still provide snow for much of the U.S. along and north of I-40 but the focus of the

heaviest snowfall would be further south than first thought, near the Ohio River. The track would also shift the potential accumulating snowfall further south, too.
For the Tennessee valley, Christmas Eve will be a cloudy day with rain arriving late. The timing of the arrival of the storm has slowed quite a bit.
For friends and family in the St. Louis area, snow, possibly briefly mixed with sleet, will begin during the

morning hours across eastern Missouri. The precipitation will quickly become all snow as some

evaporational cooling takes affect. Snow would likely continue through much of the evening hours. Based

on today’s thoughts, the heaviest snowfall will like fall near the I-44 corridor but if the trend would continue southward or if the ECMWF solution would be correct, the heavy snow band would likely form near the

Arkansas border.

Cloudy with Rain Becoming Likely towards Evening (70%)
Low: 30 High: 49

Below are some of the snowfall forecasts from the individual models. I am providing the different im

ages as a way to illustrate how things differ amongst the models and the model within itself. Notice the difference between the two different NAM and GFS runs which took place just 6 hours apart from this morning into this afternoon. This helps to show why it is still too early to put accumulation forecasts out with confidence. However, as this is an important day(s) for many I will do my best and on Wednesday, I will put out my official first numbers for this storm system.

18z NAM Snow Cover Forecast for Christmas Eve Evening

12 z NAM Snow Cover Forecast for Christmas Eve evening

18z GFS Snow Cover Forecast for Christmas Eve Evening

12z GFS Snow Cover Forecast Christmas Eve evening

Christmas Day
The GFS remains the furthest north and the ECMWF the furthest south with the CMC a good compromise, for now. That would allow for rain to change to snow in northern Alabama by sunrise and continue through much of the day.It doesn’t appear like heavy snow would be expected by some light snow is possible that may provide for some minor accumulations, especially in the mountains of

northeast Alabama. Again, this is all highly dependant on the storm track and its strength and it is still too

far out to pin point that information down. One thing that can be predicted with confidence is that it will be much colder.

18z GFS Christmas Morning Snow Cover Forecast

12z GFS Christmas Morning Snow Cover Forecast

Cloudy with rain changing to Snow Showers/Flurries (80%), Much Colder and Windy.
Low: 30 High: 35

Sunday
Since the models are slowing the progress of the system down it appears the worst of the storm will hold until the day-after Christmas for the Eastern Seaboard. A very large and powerful storm with disruptive travel likely appears to be brewing for much of the I-95 corridor.

The Tennessee Valley will be in the depth of the deepening trough over the Eastern U.S. and will experience a cloudy, raw day with occasional flurries. In fact, much of the U.S. east of the Mississippi River will be experiencing the same.

Variably Cloudy with a few flurries possible (20%), Blustery and Cold
Low: 25 High 35

Monday
Modelling data continues to indicate the possibility of several upper waves of energy pivoting around the west side of the trough from the Great Lakes down through the Mid-Mississippi Valley and then into the Ohio and Tennessee Valleys. This would help to provide for clouds moving back in after briefly clearing and to provide for additional snow showers/flurries scattered about.

Variably Cloudy and Cold, A Few Flurries possible (20%)
Low: 22 High: 35

Tuesday
Mostly Sunny
Low: 20 High: 38

Wednesday
Partly Cloudy
Low: 23 High: 46

Thursday
Mostly Cloudy, Chance For Showers
Low: 28 High: 45

Many to Be Eclipsed in Viewing the Lunar Eclipse

Then Attention Turns To Christmas Eve/Day Winter Event

Tuesday
Unfortunately abundant cloud cover across much of the U.S., especially from the Upper Midwest

southward through the Mid-Mississippi Valley and into the Lower Mississippi Valley and from the four corners west along most of the Pacific Coast, will cause viewing tonight’s total lunar eclipse to likely be missed.

What a shame because not only this the first lunar eclipse in two years but it is also the first

lunar eclipse to occur on the Winter Solstice since 1638.
For Tuesday, weak ridging will be in place over the Valley and that will help to keep temperatures mildly seasonal but at the same time a weak surface wave will be approaching the Valley from the west. This wave will help to spur a few scattered rain showers across the Tennessee Valley. Light rain showers will continue into the Ohio Valley and snow will fall further north, generally north of I-80.

Cloudy and breezy with scattered showers possible (40%)

Low: 38 High: 53 (South 5-15)

Wednesday
As the weak wave and upper level support further north into the Great Lakes passes eastward Tuesday night through Wednesday morning, a trailing cold front will slide through the Valley. This will allow a brief

return of colder air to flow back into the southern-middle Tennessee and northern Alabama. It appears the clouds will hang tough and a few morning showers will be also possible. The clouds combined with the colder air filtering into the Valley will allow for temperatures to step backwards through the day.

At the same time, an area of low pressure and upper level support will move onshore into California. As it does, it will continue to bring a large swath of rain and mountain snow to much of the Western U.S. This area of disturbed weather will become the main focus regarding the weather for much of the Eastern U.S. for the upcoming Christmas Eve/Christmas Day holidays.

Mostly Cloudy with a few scattered morning showers (30%). Turning colder and breezy with temperatures falling through the day.
Low 55 High: 44 (North 5-10)

Thursday
As the storm moves east into the eastern slopes of the Rockies, cyclogenesis is expected and strengthening, too, over the High Plains. This will likely set-up a widespread wintry event for much of the Northern Plains and Upper-Midwest, with snow along and north of I-80 and a wintry mix further south towards the I-70 corridor. Rain will then set up further south through the I-35 corridor in Oklahoma and Texas.

All the long range models are in pretty good agreement with the forecast into Thursday. They appear a bit stronger, tad further south and a touch slower than yesterday’s forecast for Thursday but the day-to-day change is minimal.

Still believe the Valley will see a day in which we will see temperatures moderate and quite a bit of sun to

be around. Likely it will be the last sunny day for several for the region as it will become unsettled as the storm arrives.

Mostly Sunny

Low 29 High:48

Christmas Eve
All the excitement begins for not only the kiddos but also the meteorologists and those wishing for a “White Christmas”, Christmas Eve. All of the models today are making the wave moving east stronger and taking it further south between the I-40 and I-20 corridors. This sets up a very “White” scenario for many along and north of the I-70 corridor. Since I have several readers from the Midwest in addition to those in the Tennessee Valley let me provide some specifics for all.

Right now, my believe is that locations along and north of I-80 will see all snow with this storm. Those between the I-70 and I-80 corridor from the Plains to the Mississippi River will likely see a wintry mix

mainly of sleet at the onset of precipitation with it changing over to snow. This would occur during the morning hours of Christmas Eve. The system will then track ESE and as it does the wintry precipitation progresses eastward. For friends in St. Louis, I am forecasting sleet to begin shortly before sunrise and then change over to snow by late morning. Snow would continue through the evening hours.

Now for the Tennessee Valley, if this forecast holds or if the trend to the south stays but doesn’t change but much, the chances increase for the Valley to see an accumulating snow for Christmas. Currently, my thinking is that rain will begin in the Valley during the afternoon hours. As the low passes east the rain would likely change over to light snow/snow showers Christmas Eve night into early Christmas morning.

The track of the low and upper level support will be a major factor on exactly where snow fall and how much and that is not just for the Tennessee Valley. As we continue to near the event the forecast will become more clear and more confidence can be put towards it.

Cloudy with Rain Likely (70%)
Low: 32 High: 52

Christmas Day
The storm will likely track into the Mid-Atlantic, Christmas Day, taking with it the brunt of the wintry precipitation. Behind it, conditions will turn windy and cold with pockets of snow showers/flurries.

Snow Cover Forecast for Christmas Morning (American GFS Model)

Forecast Snow Cover for Christmas Morning (Canadian GEM Global Model)

Cloudy with Snow Showers/Flurries (60%), Much Colder and Windy.
Low: 30 High: 35

Sunday
Models are trying to really slow down the upper level system and provide for a deep trough over the Eastern U.S.. For much of the Eastern U.S. it would be cold and blustery with pockets of snow showers/flurries. Don’t see much difference for the Valley.

Variably Cloudy with a few flurries possible (20%), Blustery and Cold
Low: 22 High 35

Monday
Models trying to show yet another piece of Pacific energy being mixed into the trough in the East and have it dip southeast out of the Plains. For now believe the Valley will see a mix of sun and clouds but still be in the cold.

Partly Cloudy and Cold Still
Low: 20 High: 38

Tuesday
Mostly Cloudy with a chance for light snow (30%)
Low: 27 High: 38

Wednesday
Partly Cloudy
Low: 31 High: 46

Thanks for reading and be safe,

"Doppler" Dale