Deep South Winterwx Discussion 2015-2016

[Brent]

12z GFS...been consistent in bringing snow to the Gulfcoast..

http://www.twisterdata.com/data/models/ ... URFACE.png

http://www.twisterdata.com/data/models/ ... URFACE.png

Those charts look MIGHTY suspicious as far as snow on the Gulf Coast from MS to FL Panhandle, even north of the FL Panhandle into southern Alabama. Look at the accumulation chart THEN look at the same model's sounding for when the snow is supposed to be falling. The soundings show a layer of warm air a few thousand feet thick at the surface in those areas. That would mean cold rain, not snow. GFS was forecasting a similar 1" (or more) snow with Tuesday's system and the actual accumulation area was north of the 1" projected area.

Agree strongly. I don't buy snow on the coast in the least, I think it's gonna be borderline even up here and I'm north of Montgomery 4 hours inland.

Those accumulation maps are hideously wrong usually.

[wxman57]

12z GFS...been consistent in bringing snow to the Gulfcoast..

http://www.twisterdata.com/data/models/ ... URFACE.png

http://www.twisterdata.com/data/models/ ... URFACE.png

Those charts look MIGHTY suspicious as far as snow on the Gulf Coast from MS to FL Panhandle, even north of the FL Panhandle into southern Alabama. Look at the accumulation chart THEN look at the same model's sounding for when the snow is supposed to be falling. The soundings show a layer of warm air a few thousand feet thick at the surface in those areas. That would mean cold rain, not snow. GFS was forecasting a similar 1" (or more) snow with Tuesday's system and the actual accumulation area was north of the 1" projected area.

Agree strongly. I don't buy snow on the coast in the least, I think it's gonna be borderline even up here and I'm north of Montgomery 4 hours inland.

Those accumulation maps are hideously wrong usually.

I wonder if the algorithm in the model for estimating accumulated snowfall needs a bit of adjusting for coastal areas of the Gulf? It seems to predict accumulating snow with the boundary layer air far too warm.

[Ivanhater]

Well damn...hopefully the models trend colder like they did with the last snow storm a couple weeks ago

[CYCLONE MIKE]

All mention of snow taken out of our forecast here in SE LA for tonight/tomorrow morning and for this coming monday night/tuesday morning. As I said earlier this week I was not getting my hopes up, and would believe it when I saw it, because I thought it was going to be just to warm. We had our snow early this winter it is time to move on with severe weather season. Should only be about 2-3 weeks away.

[Dean4Storms]

Just not enough cold air at the surface. I think the snow threat is over for the immediate Gulf Coast the rest of this year. Points about Jackson, MS to Montgomery, AL and all north from there look more likely to see any snow.

[srainhoutx]

You folks are battling the same thing we were in SE TX early in the week. Boundary layer (BL) will be critical IMHO.

[Ivanhater]

As suspected, the NAM has really trended colder with the freeze line. Low further south and stronger on this run..Good for bringing down the colder air further south.



Nice snow on the Comma head in Southern Louisiana, that is what happens when you get a strong low

[Ntxw]

Surface boundary temperatures are still warm on the 0z NAM. Aloft would be cold enough (as shown by the 850mb 0c line), but shows no real accumulation anywhere in the south. This could change though if you get heavy enough bursts of precip or if future runs shows a colder scenario. Here's a sounding for McComb, MS which is in the wrap around area with the coldest air for the system at 84hr.

[Ivanhater]

Yeah, but the NAM has trended colder. Hopefully it will continue tomorrow

[Ivanhater]

This for tonights system...seems crazy, but it matches with the GFS ouput model

[Brent]

Man the NAM is epic here, but it's really borderline on temps. If it's cold enough... holy crap.

[Brent]

My brand new forecast:

Monday Night...Rain showers in the evening...then rain and snow likely after midnight. Lows in the lower 30s. Chance of precipitation 80 percent.

Tuesday...Colder. Rain or snow likely in the morning...then chance of rain and snow in the afternoon. Highs in the lower 40s. Chance of precipitation 60 percent.

Tuesday Night...Cloudy with a 20 percent chance of rain or snow. Lows around 30.

[wxman57]

Neither the 00Z nor the 06Z NAM has any accumulating snow in MS, AL or FL (http://www.twisterdata.com/). GFS shows a small area of snow over SW Alabama and the FL Panhandle today - BUT temps at the surface and quite "warm" and the GFS sounding has the freezing level up at 5000 ft. Looking at current surface temps where the rain is falling I see low to mid 40s. So it looks like cold rain for the area today.

[Brent]

[Brent]

If it's cold enough... holy cow! We could have the biggest snowstorm since 1993.

[Brent]

NWS not impressed:

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BIRMINGHAM AL
112 PM CST SUN FEB 28 2010

ALZ011>015-017>029-031>037-010600-
MARION-LAMAR-FAYETTE-WINSTON-WALKER-BLOUNT-ETOWAH-CALHOUN-
CHEROKEE-CLEBURNE-PICKENS-TUSCALOOSA-JEFFERSON-SHELBY-ST. CLAIR-
TALLADEGA-CLAY-RANDOLPH-GREENE-HALE-PERRY-BIBB-CHILTON-COOSA-
TALLAPOOSA-
INCLUDING THE CITIES OF...HAMILTON...SULLIGENT...VERNON...
FAYETTE...DOUBLE SPRINGS...JASPER...ONEONTA...GADSDEN...
ANNISTON...CENTRE...HEFLIN...CARROLLTON...TUSCALOOSA...
BIRMINGHAM...HOOVER...COLUMBIANA...PELHAM...ALABASTER...
PELL CITY...MOODY...TALLADEGA...SYLACAUGA...ASHLAND...ROANOKE...
EUTAW...GREENSBORO...MOUNDVILLE...MARION...CENTREVILLE...
CLANTON...ROCKFORD...ALEXANDER CITY...DADEVILLE
112 PM CST SUN FEB 28 2010

...WINTER PRECIPITATION POSSIBLE MONDAY NIGHT INTO TUESDAY...

A STRENGTHENING LOW PRESSURE SYSTEM WILL CROSS THE NORTHERN GULF
OF MEXICO MONDAY AND ACROSS NORTHERN FLORIDA BY TUESDAY AFTERNOON.
AHEAD OF THIS SYSTEM...MOISTURE WILL SPREAD INTO CENTRAL ALABAMA
MONDAY AFTERNOON RESULTING IN WIDESPREAD RAINFALL. COLDER AIR WILL
FILTER INTO THE AREA MONDAY NIGHT FROM THE NORTHWEST...RESULTING
IN THE POSSIBILITY OF WINTER WEATHER.

AT THIS TIME...RAIN IS EXPECTED TO TRANSITION TO SNOW ALONG AND
NORTH OF A LINE FROM EUTAW TO CLANTON TO ROANOKE EARLY TUESDAY
MORNING...CONTINUING THROUGH THE MORNING HOURS AND ENDING FROM
WEST TO EAST DURING THE EARLY AFTERNOON. DUE TO WARM GROUND
TEMPERATURES...SNOWFALL ACCUMULATIONS MAY BE LIMITED...WITH LESS
THAN AN INCH EXPECTED ACROSS THE AREA. IN THE HIGHER ELEVATIONS OF
NORTHEAST CENTRAL ALABAMA...AROUND ONE INCH WILL BE POSSIBLE.

CONSIDERABLE UNCERTAINTY REMAINS WITH THIS SYSTEM...AND MINOR
CHANGES IN STORM TRACK AND INTENSITY COULD HAVE A SIGNIFICANT
IMPACT ON THE POSSIBILITY OF WINTER PRECIPITATION. THE RAIN SNOW
TRANSITION LINE AND ACCUMULATION TOTALS WILL LIKELY NEED TO BE
REFINED WITH FUTURE FORECASTS. CENTRAL ALABAMA SHOULD STAY TUNED
FOR UPDATES ON THIS DEVELOPING WINTER WEATHER SITUATION.

$$

14

[Brent]

Monday Night...Rain likely in the evening...then snow and rain likely after midnight. Little or no snow accumulation. Lows in the lower 30s. Northeast winds 5 to 10 mph. Chance of precipitation 70 percent.

Tuesday...Colder...snow. Near steady temperature in the mid 30s. North winds 10 to 15 mph. Chance of snow near 100 percent.

[jinftl]

NWS Birmingham has been putting out great Discussions....they discuss the limitations and room for error and changes as just a small change in forecast atmospheric conditions can lead to the difference between 'that's it until next winter folks' and what could be the last winter weather event for the season in the northern areas of the Deep South (fyi....temps next
weekend in Birmingham are forecast to reach the mid 60's under fair skies...Montgomery could approach 70 deg).


AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BIRMINGHAM AL
1003 PM CST SUN FEB 28 2010

.DISCUSSION...


HAVE SPENT MOST OF THE NIGHT LOOKING AND ANALYZING THE MODELS TO SEE
IF THERE IS A BETTER SOLUTION OUT THERE OR AT LEAST SOMETHING TO
MAKE ME FEEL A LITTLE BETTER. THE GOOD NEWS WAS THAT THE 18Z RUNS
WERE REALLY SIMILAR TO THE 12Z RUNS...SO CAN NOT DISAGREE TOO MUCH
WITH THE CURRENT FORECAST. HOWEVER THE 00Z RUNS ARE BEGINNING TO
COME IN...WILL ALLOW THE MIDNIGHT SHIFT TO TAKE A GOOD LOOK AT THESE
RUNS FOR BETTER COMPARISON.

THE MAIN CONCERN THAT WE STILL HAVE WILL BE THE GROUND TEMPERATURES
AND WHAT ACCUMULATION WE MAY ACTUALLY GET. MOISTURE WILL NOT BE
LACKING WITH THIS SYSTEM...OUTSIDE OF THE EXTREME NORTHWESTERN
SECTIONS OF THE CWA. THE UPPER AND SURFACE LOW TRACKS ARE IN A
FAVORABLE POSITION WITH EVEN A DECENT WRAP AROUND DEFORMATION ZONE
OF LIFT THAT TRIES TO GET GOING AS THE SECONDARY PUSH OF UPPER LEVEL
DYNAMICS WORKS THROUGH THE AREA TUESDAY MORNING. LOOKING AT AREAS OF
POSSIBLE FRONTOGENESIS...ONE WOULD FOCUS ACROSS NORTHERN AND CENTRAL
ALABAMA BETWEEN THE 3 AM AND 12 PM TIME PERIOD FOR THE BEST LIFT
OVER THE AREA. HOWEVER EACH MODEL DEPICTS ITS OWN PLACEMENT FOR THIS
DEVELOPMENT...AND ARE NOT THAT AGREEABLE ON ITS LOCATION. ANOTHER
CAVEAT TO THIS WOULD BE THE EURO. THE LATEST 12Z RUN WOULD BE A
DISAPPOINTMENT TO MOST SNOW SEEKERS. WHILE NOT A ZERO AMOUNT OF
ACCUMULATION...A DUSTING WOULD BE GENEROUS.

QUESTIONS THAT WERE IN THE PREVIOUS FORECAST ARE STILL THERE AS OF
THIS UPDATE. WILL THE COLDEST AIR WORK IN BEFORE IT IS TOO
LATE...AND WHAT WILL BE THE MAIN SNOW MAKER. WILL WE GET THE SNOW ON
THE BACKSIDE OF THE FIRST WAVE OR WILL WE HAVE TO WAIT FOR THE
SECONDARY COLD AIR PUSH WITH THE UPPER LOW TO GET THE BEST
ACCUMULATION.

THIS SECONDARY PUSH OF COLD AIR THAT WILL EVENTUALLY CHANGE THE RAIN
TO SNOW...REMAINS MARGINAL...AT BEST. THIS KEEPS THE FORECAST IN
LIMBO EVEN AS WE GET CLOSER TO 24 TO THE 30 HOUR WINDOW FOR THE
ONSET OF THE POSSIBLE SNOW. WE WILL MOST LIKELY END UP RELYING
MOSTLY ON THE DYNAMICAL COOLING EFFECT...WHICH WILL MEAN WE NEED A
BETTER THAN MODERATE RATE OF PRECIPITATION FALLING THROUGH THE LAST
FEW THOUSAND FEET. LOOKING AT SOUNDING THIS COULD BE AS MUCH AS 3 TO
4 THOUSAND FEET AT THE ONSET...THEN REDUCING DOWN TO 2500 FEET. IT
WILL BE HARD TO GET A DECENT AMOUNT OF ACCUMULATION WITH THIS
DISTANCE TO TRAVEL DOWN.

WITH THAT SAID...THERE IS A CHANCE OF SOME ACCUMULATING SNOW ACROSS
PORTIONS OF CENTRAL ALABAMA ON TUESDAY. AT THIS TIME...THE BEST
CHANCE FOR SNOW IS ALONG AND NORTH OF A LINE FROM EUTAW...TO
CLANTON...TO ROANOKE...FROM 4 AM THROUGH 6 PM TUESDAY. WITH THE
HIGHEST TOTALS LIKELY IN THE HIGHER ELEVATIONS IN THE NORTHEAST...
WHERE THERE WILL BE LESS DISTANCE FOR THE PRECIPITATION TO FALL THAT
WILL BE ABOVE FREEZING.

THE CURRENT FORECAST IS FOR ONE INCH OR LESS OF SNOW IN THESE
AREAS. HOWEVER...THIS FORECAST IS BASED ON TEMPERATURES STAYING JUST
WARM ENOUGH SO THAT MOST OF THE SNOW THAT DOES FALL WILL QUICKLY
MELT. HOWEVER...IT WOULD TAKE A TEMPERATURE DROP OF JUST 2 OR 3
DEGREES TO CAUSE THESE AMOUNTS TO INCREASE SIGNIFICANTLY.

NOW THROW IN THE LATEST NAM WITH A FURTHER SOUTH SOLUTION...AND
CONFIDENCE DECREASES EVEN MORE. AT THIS TIME WILL LEAVE THE FORECAST
AS IS AND WAIT TO COMPARE 00Z RUNS TO EACH OTHER. CONFIDENCE IS NOT
HIGH ENOUGH TO ISSUE ANY WINTER STORM WATCHES AT THIS TIME. ANY
WINTER WEATHER ADVISORIES ARE USUALLY ISSUED WITHIN A 12 TO 24 HOUR
PERIOD...SO WILL HOLD OFF ON THOSE AS WELL. WE WILL BE UPDATING THE
SPS TO HIGHLIGHT THE CONCERNS. UPDATES TO THE FORECAST HAVE BEEN
SENT.

[Brent]

Birmingham has been putting out awesome discussions given the setup. This is an impossible forecast, but I will say, I have a feeling at least that the highest elevations above 1,500 feet just north of here may see a significant snow(more than 2-3 inches). It could even be a situation where the lower elevations don't see a flake. Nothing would surprise me at this point and I'm fully expecting to travel towards the highest elevations to see it.

That said... the 0z models strongly suggest this could be a significant snow even in the lowest elevations, and possibly a massive snow over 6-8 inches in the higher elevations(especially in Georgia north of Atlanta). We'll see... this storm has been very high bust potential and I wouldn't be surprised to see a lot of nowcasting and warnings go up at the last minute late tomorrow or even early Tuesday.

[Brent]

Well I've decided to make a call map... this is about the most impossible forecast I've ever seen. I'm more aggressive than the NWS but not as aggressive as I wanted to be due to warm air/ground temps. On the other hand, I could be too low on totals because of very heavy rates overcoming the negatives. Very tough forecast.