Heavy Snow threat 2/9/11-2/10/11 AR AL MS TN

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James Spann | 1:04 pm February 5, 2011 | Comments (2)
Yet another challenging week ahead for Alabama meteorologists. Everybody is looking for answers that quite frankly can’t be handled very well more than 48 hours in advance. I am getting email and Facebook and Twitter messages from people telling me that various people are forecasting a “historic” snow for Alabama this week, and they want to know what I think.
Long time blog readers know my usual response… I honestly don’t care about what anybody else says, I simply don’t have the time or interest. All we do here is tell you what we think will happen with full explanation and openness.
This is where we are right now…
MONDAY: The first wave of the week will bring some light rain to the state Monday, with some risk of a little light snow on the back side of the departing system Monday evening. Here is the RPM output below for 4:00 p.m. CST Monday… showing the most widespread snow over the northern quarter of the state, and it is very light…

There could be a dusting of snow for that part of Alabama Monday evening, but precipitation should be pretty light.
WEDNESDAY/THURSDAY: If we are going to get a big winter storm, this is the time. Again, there is not much skill in forecasting snow placement and amounts more than 48 hours in advance around here. Why some people choose to do it is a little baffling.
The GFS has been advertising a big North Alabama snow for a number of runs, but it has backed off in recent runs. Below is a look at the forecast snow for Birmingham from the GFS using BUFKIT data:

The last few GFS runs, as you can see, are now printing only a dusting to 1.2 inches for Birmingham. Runs from yesterday were in the 6 to 10 inch range.
The ECMWF, which has performed pretty well this season, is now more aggressive. Below is the output valid Thursday morning at 6:00 a.m. CST…

That would suggest a very good snow for the northern third of Alabama.
BIG TIME COLD: Aside from the snow, some very cold air will come in here late in the week… you can see the GFS in recent runs is suggest mid-teens by Friday morning… the runs were colder yesterday with 0 degrees (F) showing up…

BOTTOM LINE: There is a chance of some significant snow for parts of Alabama (most likely the northern counties) Wednesday night into Thursday morning, but it is way too early to be specific on amounts or placement. And, it will turn much, much colder at the end of the week, perhaps the coldest air so far this season.
All of the armchair meteorologists will probably make wild forecasts of big snow, and who knows, they might right, but NOBODY right now knows. I recommend this weekend you spend some time with your family, take a long walk, get a little fresh air, and relax. The 48 hour rule means the first snow accumulation potential graphic won’t show up here until Monday night, most likely.
Enjoy the weekend!!!!

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Late Night Forecast Thoughts…

Bill Murray | 12:16 am February 6, 2011 | Comments (11)
Everyone wants to know if we are going to have a monster snow Wednesday and Thursday. That idea has been on the table since it was a feature of a few GFS and European model runs this week. While the models have backed off from this solution over the past several runs, this has been the winter of the unexpected. We will actually deal with a minor winter threat tomorrow night with the main even coming Wednesday night and Thursday followed by some cold conditions for late in the week and the weekend. How cold? How much snow? Let’s see what we can tell…
TONIGHT/MONDAY: Clouds will thicken this evening and a few showers may arrive by midnight. Dewpoints are in the upper 20s already, so cooling by evaporation will not be a problem tonight. Temperatures will drop into the lower 40s before skies cloud over, and this should keep the precipitation liquid through much of the overnight hours. The approaching disturbance will cool the mid levels of the atmosphere, setting the stage for the precipitation to mix with or briefly change over to snow by late in the day Monday. In any case, temperatures will be in the lower and middle 40s on Monday, preventing any accumulation issues. A brisk westerly wind will kick in by afternoon. As skies start to clear Monday night, lows will fall back into the upper 20s.
WEDNESDAY NIGHT
Precipitation is expected to begin before midnight across North and Central Alabama Wednesday night. It looks like it will be snow over the north, with a rain/snow mix over Central Alabama. Rain will likely change to or be all snow all the way down to the I-20 corridor Wednesday night. Lows will drop to near freezing in the I-20 corridor, with colder readings to the north and warmer conditions to the south. Thursday will feature colder conditions

ACCUMULATIONS: It’s still too early to try to be specific about snow accumulations for Wednesday night and Thursday. Recent model runs have not shown the signs of a huge accumulating snow, with the best moisture south of the colder temperature profiles. But the idea of there being a few hours of light snow in areas north of I-20 is a good possibility. This is what the accumulated snow chart looks like from the evening GFS run. This looks like a very plausible solution to me.
TURN TO COLDER: Thursday will feature colder conditions with a brisk northwesterly wind and temperatures rising only a few degrees at best into the middle 30s. Indeed, temperatures may remain steady during the morning hours before falling by afternoon. Lows will be in the teens by Friday morning, and should remain in the 30s during the day. Saturday will be slightly warmer. Sunday looks a lot like Saturday.

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NAM Cold, Wet (Snowy) for Wednesday Night

Bill Murray | 9:11 pm February 6, 2011 | Comments (7)
The evening run of the NAM is coming in wet and cold for Wednesday night, giving more confidence to a snowy forecast for late Wednesday night for Central Alabama.
Here is the precipitation and 850 mb 0C isotherm for midnight Wednesday night. It shows snow spreading into areas north of US-82 and I-20. The 850 mb temp is the temperature at 5,000 feet. It is a good rule of thumb for the rain/snow line. If the NAM verifies, we could see a general 2 to 4 inch snowfall across North Central Alabama Wednesday night.
We are still dealing in speculation based on model data at this point. We will start to deal in specific forecasts by tomorrow night.

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Nashville :(

ON WEDNESDAY...DEVELOPING SFC/LL LOW WILL MOVE INTO THE WESTERN GULF
AND CONTINUE EASTWARD TRACK WEDNESDAY NIGHT. DEEPER MOISTURE WILL BEGIN
SPREADING INTO THE AREA DURING THE DAY...WITH SNOW AND/OR MIXED
PCPN BREAKING OUT IN THE AFTERNOON. WEDNESDAY NIGHT...BRUNT OF SNOWFALL
EXPECTED...WITH SEVERAL INCHES STILL POSSIBLE ALTHOUGH GFS CONTINUES
TO BACK OFF OF BIG EARLIER AMOUNTS PUSHING GULF LOW FURTHER AND FURTHER
SOUTH.

LONG TERM...
ISO-SCT LIGHT SNOW SHOWERS WILL LINGER WELL INTO THURSDAY...ENDING
LATE AFTERNOON EAST. LITTLE ADDITIONAL ACCUMULATION EXPECTED THURSDAY
ALTHOUGH MAYBE THE PLATEAU PICKS UP ANOTHER HALF TO INCH OR SO.

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[Joe-Nathan]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LAKE CHARLES LA
616 AM CST MON FEB 7 2011

...COLDER AIR SPILLING INTO THE REGION BEHIND THE FRONT LOOKS TO
OVERLAP WITH ENOUGH RESIDUAL MOISTURE TO PROVIDE AT LEAST A CHANCE
OF WINTER PCPN OVER PARTS OF THE AREA PER PARTIAL THICKNESS
METHOD. A DEEPER EXAMINATION VIA MODEL TIME HEIGHTS/SOUNDINGS
AND THE TOP DOWN METHOD INDICATE A COLD RAIN GIVEN THE LACK OF ICE
INTRODUCTION ALOFT. FORECAST SURFACE TEMPERATURES OVER THE EAST
TEXAS LAKES REGION INTO CENTRAL LOUISIANA ARGUE FOR A CHANCE OF
FREEZING RAIN/DRIZZLE BEFORE LIFT COMES TO AN END THURSDAY
MORNING. PREVIOUS FORECAST HAD A SLIGHT CHANCE/CHANCE OF RAIN OR
FREEZING RAIN MENTIONED...AND THIS STILL LOOKS REASONABLE. NO
SIGNIFICANT ACCUMULATIONS ARE EXPECTED...

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Jackson MS

WEDNESDAY THROUGH NEXT SUNDAY...

BY FAR THE PRIMARY CONCERN LATER IN THE WEEK WILL BE THE POTENTIAL
FOR ACCUMULATING SNOWFALL FROM LATE WEDNESDAY INTO EARLY THURSDAY.
CONFIDENCE IS INCREASING THAT NORTHWEST PORTIONS OF THE
ARKLAMISS...ESPECIALLY OVER THE UPPER DELTA REGION...COULD RECEIVE
AROUND 2 TO 4 INCHES OF SNOWFALL...WITH LIGHTER AMOUNTS POSSIBLE AS
YOU GO FARTHER SOUTHEAST.

MODELS...ESPECIALLY THE GFS...HAVE TRENDED DRIER OVER THE PAST
COUPLE OF DAYS DUE TO THEIR QUICKER DAMPENING OF THE SHORTWAVE TROUGH
RESPONSIBLE FOR THIS POTENTIAL SNOW EVENT. BASED ON RECENT
SIGNIFICANT TROUGH PASSAGES...BELIEVE THERE WILL BE LESS PHASING OF
THE STREAMS THAN INDICATED BY THE GFS...THUS RESULTING IN A MORE
DISTINCT TROUGH PASSAGE AND MORE PERSISTENT WARM ADVECTION AND LARGE
SCALE ASCENT - SO HAVE RAISED MAV MOS GUIDANCE POPS AND GFS QPF
CONSIDERABLY AS A RESULT FOR WED-WED NIGHT.

PRECIPITATION TYPE WILL BE EITHER RAIN OR SNOW WITH THIS SYSTEM AS
DEEP COLD AIR MOVES INTO THE ARKLAMISS AT THE SAME TIME THAT SURFACE
LOW PRESSURE DEVELOPS OVER THE NORTH CENTRAL GULF. IN GENERATING THE
FORECAST GRIDS FOR SNOW VS RAIN...HAVE FOLLOWED A BLEND OF THE
ECMWF/SREF AND THEIR CONSENSUS 1200 FT AGL WET BULB ZERO HEIGHT
LOCATION. IT IS POSSIBLE THAT PRECIPITATION WILL BEGIN AS SNOW OVER
UPPER THE DELTA REGION WEDNESDAY AFTERNOON...BUT GENERALLY EXPECT
PCPN TO BEGIN AS RAIN BEFORE EVAPORATIVE COOLING/MELTING ALOFT CAN
LEAD TO A CHANGE-OVER TO SNOW AS THE BOUNDARY LAYER COOLS. THE
BEST FRONTOGENETICAL FORCING AND COLDEST AIRMASS WILL COINCIDE OVER
THE UPPER DELTA REGION AND THIS IS WHERE THE HEAVIEST SNOW
ACCUMULATION IS ANTICIPATED. ELSEWHERE...WEAKER MOISTURE TRANSPORT
AND LESS EFFICIENT SNOW PRODUCTION WILL LEAD TO LIGHTER AMOUNTS.

THERE IS STILL MUCH THAT COULD CHANGE REGARDING POTENTIAL SNOWFALL
AMOUNTS SHOULD THE TROUGH MAINTAIN MORE/LESS INTEGRITY THAN THE
MODELS SUGGEST. FOR NOW WILL RAMP UP THE WORDING IN THE HWO TO
REFLECT HIGHER CONFIDENCE IN ACCUMULATING SNOWFALL...PARTICULARLY
OVER THE UPPER DELTA REGION.

THURSDAY AND BEYOND...THE LOW PRESSURE SYSTEM WILL BE QUICK-HITTING
AND PRECIPITATION WILL WIND DOWN QUICKLY THURSDAY MORNING WITH A
STRONG COLD ADVECTION PATTERN TO FOLLOW. VERY CHILLY CONDITIONS WILL
PERSIST THROUGH FRIDAY...BUT A SIGNIFICANT WARM-UP IS STILL ON TAP
FOR THE WEEKEND AS ZONAL FLOW SETS UP AND BRINGS MILD PACIFIC AIR
INTO THE REGION. /EC/

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James S

*WEDNESDAY NIGHT: This is when we have a much better chance of accumulating snow. Hot off the presses is the 12Z RPM snow accumulation chart, valid through 6:00 a.m. Thursday:

This tends to validate the idea of 1-2 inches of snow for much of North Alabama, generally north of I-20, with a dusting down to a line from Livingston to Clanton to Roanoke.
We also note the 12Z NAM is more aggressive, with 2-4 inches for North Alabama (the heaviest axis of snow is north of a line from Fayette to Warrior to Jacksonville…

I will have the first snow accumulation potential graphic up later this afternoon

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[Joe-Nathan]

WINTER STORM WATCH FROM SHREVEPORT:

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SHREVEPORT LA
317 PM CST MON FEB 7 2011

DISCUSSION

WINTER STORM WATCH WILL BE GOING OUT WITH THIS PACKAGE AND HAD TO
SEGMENT THE PRODUCT DUE TO TIMING ISSUES. THE WATCH BEGINS ACROSS
THE NORTHERN TWO THIRDS OF NE TX...SE OK AND EXTREME SW AR AT
06Z WED AND HAVE EXPANDED THE WATCH EASTWARD TO INCLUDE THE
REMAINING PORTIONS OF SW AR AND THE NORTHERN TWO THIRDS OF N LA
BEGINNING AT 12Z WED. THE WATCH WILL EXPIRE AT 00Z THU.

CONTINUED TO USE A COMBINATION OF THE GFS/ECMWF/CANADIAN MODEL
CONCERNING THE SYSTEM TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. THE
ECMWF TIMING IS A LITTLE SLOWER THAN THE OPERATIONAL GFS BUT STILL
SUPPORTS OUR THINKING OF A BIG WINTER WEATHER EVENT TAKING SHAPE
DURING THE DAY WEDNESDAY. 6HR GRIDDED WEATHER FORECAST BEST
REPRESENTS THE CHANGE OVER WHICH WILL OCCUR FROM WEST TO EAST
ALONG THE I-20 CORRIDOR WHILE FURTHER NORTH...THE EVENT WILL BE
MAINLY A SNOW EVENT. FOR NOW...WE ARE ADVERTISING 4-6 INCHES
ACROSS ALL OF S AR...THE NORTHERN THIRD OF NE TX AS WELL AS SE OK.
FURTHER SOUTH ALONG THE I-20 CORRIDOR OF NE TX INTO N LA...WE ARE
ADVERTISING 2-4 INCHES OF SNOW WITH SOME MINOR ICE ACCUMULATIONS
MAINLY IN THE FORM OF SLEET. CANNOT RULE OUT SOME PATCHY FREEZING
RAIN HERE AND THERE BUT THE COLD AIR ARRIVES SO QUICKLY BEHIND THE
ONSET OF PRECIPITATION...BELIEVE ANY WINDOW OF OPPORTUNITY FOR
FREEZING RAIN WOULD BE BRIEF. IT MUST BE NOTED THAT HIGH
TEMPERATURES WILL LIKELY BE REACHED WEDNESDAY MORNING WITH FALLING
TEMPERATURES DURING THE DAY AS THE PRECIPITATION COOLS THE COLUMN.

THE SETUP IS AN UPPER LEVEL TROUGH WHICH WILL CONTINUE TO DIG INTO
THE SOUTHERN GREAT BASIN ON TUESDAY BEFORE EJECTING OUT INTO THE
SOUTHERN PLAINS LATE TUESDAY NIGHT INTO WEDNESDAY. 850MG LOW
PRESSURE FOR THIS EVENT MOVES MAINLY WEST TO EAST ALONG THE I-20
CORRIDOR WITH THE 850MB 0 DEGREE ISOTHERM ALMOST PARALLELING THE
CORRIDOR WITH FLUCTUATIONS NORTH AND SOUTH DURING THE MORNING
WEDNESDAY. JUST HOW THE TEMPERATURE PROFILE COOLS OR WARMS AT
THIS LEVEL WILL MEAN THE DIFFERENCE IN ALL SNOW VS A MIXTURE SO
THIS FORECAST WILL CONTINUE TO BE FINE TUNED AS IT GETS CLOSER IN
TIME. ONE THING THE MODELS DO AGREE ON IS THE 850MB 0 DEGREE
ISOTHERM DROPPING WELL SOUTH OF THE I-20 CORRIDOR DURING THE
AFTERNOON WEDNESDAY...RESULTING IN MOSTLY SNOW ACROSS ACROSS MOST
AREAS EXPECT PERHAPS OUR EXTREME SOUTHERN AREAS WHERE SOME SLEET
WILL BE POSSIBLE.

THE EVENT SHOULD END QUICKLY WEDNESDAY EVENING WITH COLD
TEMPERATURES IN ITS WAKE THROUGH THE END OF THE WEEK. CONTINUED TO
UNDERCUT GUIDANCE TEMPS...ESPECIALLY ACROSS OUR NORTHERN ZONES
WHERE A SNOW PACK WOULD RESULT IN COLDER THAN MOS TEMPERATURES.
STILL LOOKING AT A PRETTY GOOD WARMUP FOR THE WEEKEND WITH A DRY
FORECAST BEYOND WEDNESDAY NIGHT.

THANKS FOR THE COORDINATION FWD...LZK. PRELIMS TO FOLLOW..

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.... James is downplaying things for now

A Few Flurries Possible Tonight…

James Spann | 3:16 pm February 7, 2011 | Comments (6)
An all new edition of the ABC 33/40 Weather Xtreme video is available in the player on the right sidebar of the blog. You can subscribe to the Weather Xtreme video on iTunes by clicking here.
COLD AND ACTIVE: Much colder air is flowing into Alabama at mid-afternoon. Muscle Shoals and Haleyville have dropped into the upper 30s, and that colder air will spread over all of Alabama tonight. Support from the upper trough could squeeze out a few snow flurries this evening, perhaps as far south as Birmingham and Anniston, but they won’t amount to much. Everybody should be down in the mid 20s by daybreak tomorrow.
CALM DAY TOMORROW: Cool and dry… a partly sunny sky with a high in the low to mid 40s.
SNOW FOR WEDNESDAY NIGHT: Not much overall thinking on the snow event for North Alabama Wednesday night. Below is the first snow accumulation potential outlook…

Here is the situation…
*Snow should spread into Northwest Alabama Wednesday evening, becoming widespread by 9:00.
*The best chance of accumulating snow will be along and north of a line from Millport to Birmingham to Anniston. North of that line we are projecting average amounts of 1-2 inches, with pockets of 2-4 inch amounts across higher terrain of Northeast Alabama. Very much in line with the 12Z NAM.
*Snow flakes are possible as far south as Livingston, Brent, Clanton, Rockford, and Roanoke, but accumulation there is not likely.
*We will drop into the mid 20s Thursday morning as the snow ends (it should be over by 7:00 a.m.), so some icy travel is likely where there is accumulation early Thursday. We should warm into the upper 30s by late morning, so unless it is colder than we think, this should not be an all-day kind of issue with travel concerns.
*The coldest morning will be Friday morning, when the sky should be clear. Where snow is on the ground, lows in the teens are likely. Where there is no snow, lows will be in the 20-24 degree range.
WEEKEND WARM-UP: We are still looking at a wonderful weekend… after a low in the 20s early Saturday, we will warm to near 50 Saturday afternoon, followed by a high in the 57-60 degree range on Sunday. Dry air should mean a good supply of sunshine both days.
LONG RANGE: No doubt there will be cold snaps during the latter half of February, but with no big upper ridge over the western part of North America tapping Arctic air, it still looks like the second half of February will be milder than the first half. We can see that light at the end of this long, cold winter tunnel.
WEATHER BRAINS: Don’t forget you can listen to our weekly 30 minute netcast anytime on the web, or on iTunes. This is the show all about weather featuring many familiar voices, including our meteorologists here at ABC 33/40. We will record this week’s show tonight at 8:30 p.m. CST…

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[Joe-Nathan]

.... James is downplaying things for now

You ain't kidding.