Deep South Winterwx Discussion 2015-2016

[Ivanhater]

NWS Mobile/Pensacola still forecasting snow on Christmas night north of interstate 10, just north of the immediate coast. Well see if they hold strong.


Saturday Night: A 40 percent chance of snow before midnight. Mostly cloudy, with a low around 28. North wind between 10 and 15 mph, with gusts as high as 25 mph.

[Ivanhater]

Wow. 18z Nam is trending better. Very close to a phase and Gulf low stronger. Close call

[Ntxw]

I don't think anything major is going to change. Usually when a system is onshore the data tremendously improves the forecasting which happened last night at the time we'd expect it to with the 0z consensus and euro collapsing. Small variables will occur and now it seems cold air is the issue. It's not too tremendously cold upstream which is a setback and without a powerhouse southern storm (it's pretty weak right now) it's unlikely to do so drastically. If it does snow I think it will be from cold air squeezing out what's left behind the cold front and models have shown a dusting to maybe a few inches in the Tennessee valley.

[georgia_tech_swagger]

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
245 PM EST THU DEC 23 2010

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
-- Changed Discussion --
AS OF 235 PM THURSDAY...THE 12Z GFS AND ECM FEATURE SLOWLY
INCREASING AGREEMENT ON THE UPPER FLOW PATTERN FOR THE SYSTEM THIS
WEEKEND. THE SRN STREAM LOW CENTER OVER THE FOUR CORNERS REGION THIS
AFTERNOON WILL REACH THE WRN GULF OF MEXICO FRI NIGHT AS THE NRN
STREAM UPPER SYSTEM DEEPENS OVER THE GREAT LAKES. THIS SHOULD CAUSE
THE SURFACE REFLECTION OVER THE NRN GULF OF MEXICO TO SHUTTLE
EASTWARD FAIRLY QUICKLY ON SAT. GRADUALLY DEEPENING MOISTURE ALONG
THE BAROCLINIC ZONE BETWEEN THE TWO SYSTEMS WILL SETTLE INTO THE
REGION STARTING FRI NIGHT AND CONTINUING SAT. ALTHOUGH THICKNESSES
APPEAR A BIT MARGINAL FOR SNOW AT ONSET IN THE SE HALF OF THE
AREA...WET BULB PROFILES SUPPORT SNOW IN THE EVAPORATIONALLY COOLED
AIRMASS. QPF AMOUNTS...HOWEVER...WITH THIS INITIAL BATCH OF
FRONTOGENESIS DRIVEN FORCING SHOULD BE FAIRLY LIGHT. SNOW
ACCUMULATIONS COULD REACH 1 TO 2 INCHES IN MTNS LOCATIONS SAT...BUT
REMAIN MUCH MORE DIFFICULT TO PIN DOWN AS SLIGHT WARMING OF THE SFC
LAYER IS LIKELY ACROSS THE PIEDMONT THROUGH THE DAY...WHERE RAIN
COULD MIX IN AT TIMES. WILL CONTINUE TO FEATURE MAX TEMPS WELL BELOW
MOS GIVEN ABUNDANT CLOUDS AND AN EXPECTED PRECIP ONSET.

THE MORE INTERESTING PART OF THE EVENT WILL BE THE TRANSITION OF THE
SFC LOW FROM THE NE GULF OF MEXICO TO THE COASTAL WATERS OFF GA ON
SAT NIGHT. THE ECM REMAINS THE MOST AGGRESSIVE WITH PRECIPITATION
AMOUNTS IN THE DEFORMATION ZONE STRETCHING NW INTO THE
PIEDMONT...BUT ALL OTHER GUIDANCE SOURCES REMAIN VERY STINGY ON THE
QPF IN THE INCREASINGLY COLD AIR. THE CURRENT THINKING IS THAT EVENT
TOTALS WILL LIKELY BE LIMITED TO AN INCH OF SNOW IN MOST AREAS
OUTSIDE OF THE MTNS...WITH AMOUNTS IN EXCESS OF 1.5 INCHES POSSIBLE
FROM CHARLOTTE SE. THE ONLY CHANCE AT HEAVY SNOW OUTSIDE OF THE MTNS
APPEARS TO BE WITH ANY MESOSCALE BANDING...AND THIS IS MUCH TOO
UNCERTAIN TO FORECAST AT THIS POINT.

THE EVENT WILL TRANSITION TO NW UPSLOPE FLOW IN THE WRN NC MTNS FROM
LATE SAT NIGHT THROUGH SUNDAY. AN EXTENDED WINTER WEATHER ADVISORY
FOR SNOW WILL LIKELY BE NEEDED IN MANY MOUNTAIN LOCATIONS AT SOME
POINT FOR THIS WEEKEND...WITH THE HIGHEST ACCUMULATIONS NEAR THE TN
BORDER. HOWEVER...NO WINTER STORM WATCHES ARE NEEDED AT THIS POINT.
WILL CONTINUE THE HWO MENTION WITH ADJUSTED WORDING ON ACCUMULATIONS.
-- End Changed Discussion --

[Portastorm]

I don't think anything major is going to change. Usually when a system is onshore the data tremendously improves the forecasting which happened last night at the time we'd expect it to with the 0z consensus and euro collapsing. Small variables will occur and now it seems cold air is the issue. It's not too tremendously cold upstream which is a setback and without a powerhouse southern storm (it's pretty weak right now) it's unlikely to do so drastically. If it does snow I think it will be from cold air squeezing out what's left behind the cold front and models have shown a dusting to maybe a few inches in the Tennessee valley.

I won't quibble with the direction of your statement above as I agree with you, but as I pointed out in an earlier post today, the NCEP folks in DC this morning said that tonight's 0z runs would be the ones which reflect the most data input and that today's 12z runs would have *some* of that input.

[Ntxw]

Very good point Portastorm! Why don't we take some nowcasts and see what's going on there

[Lane]

Ivan, does this current setup remind you of the Feb snow storm last year? I want to say that low formed somewhere of the coast of LA or TX. And then headed towards Cuba? Central AL ended up seeing snow and so did FL. It all boiled down to the timing of the cold air.
Is this a similar scenario?

[Ntxw]

Ivan, does this current setup remind you of the Feb snow storm last year? I want to say that low formed somewhere of the coast of LA or TX. And then headed towards Cuba? Central AL ended up seeing snow and so did FL. It all boiled down to the timing of the cold air.
Is this a similar scenario?

This is a much different setup. Cold air was already in place for that one as the SJT streamed from Hawaii. The vigorous storm system then took advantage of that jet and tapped moisture which spread snow all across the south. For this it would come from the backside comma head (if it phases enough) rather than all snow from start to finish.

[Ivanhater]

00z models coming out and the Nam is very odd

It stalls the southern vort over Texas, but does have the northern stream further west. Very close to a phase..maybe a trend?

[Ntxw]

The northern stream is coming in too fast rather than coming behind/right at to boost. Instead of phasing, it's stronger and absorbs the southern stream. After the Texas treck, it fades away which we don't want. We want the dominant southern storm which then blows up as the northern trough feeds into it.

Minus a few details, looks similar to previous runs.

[Ivanhater]

The 00z GFS is a vast improvement from prior runs. Almost phases and much wetter. We will see if this is a trend, sure better than last night

[Ivanhater]

00z Canadian looks better as well! Hope this is a trend

[Ivanhater]

00z GFS snowfall map....see how much of an improvement. If it keeps trending the way it is, it could be game on

[Ntxw]

Lets keep our fingers crossed! Let it snow let it snow let it snow! Euro comes out soon.

[SunnyThoughts]

Guess I'll have another rum and coke, hang out and see what the euro has to say. Not getting my hopes up though. Fun to see how dynamic this system is...back and forth. Probably won't know exactly what anyone in the south will get as far as rain/snow or mix...until it actually happens.

[bella_may]

Michael do you have the updated mobile/pensacola noaa outlook?

[Ivanhater]

Drink up Sunny!

BTW while we wait on the Euro...GFS is showing a COLD start to January. Almost the entire country in the deep freeze. When again are we supposed to have a warm winter?

[sherry]

Guess I'll have another rum and coke, hang out and see what the euro has to say. Not getting my hopes up though. Fun to see how dynamic this system is...back and forth. Probably won't know exactly what anyone in the south will get as far as rain/snow or mix...until it actually happens.

For some reason that is always the case it seems for snow in the south.. I feel bad for mets in the south. It seems the more they talk about a snow the less chance of it happening and then when they only predict a little we end up with alot.

[Ivanhater]

Michael do you have the updated mobile/pensacola noaa outlook?

Here is the updated outlook Bella

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH WEDNESDAY

A STRENGTHENING LOW PRESSURE SYSTEM IS FORECAST TO MOVE ACROSS THE
NORTHERN GULF OF MEXICO ON CHRISTMAS DAY. RAIN WILL BECOME LIKELY
OVER MUCH OF THE AREA DURING THE DAY SATURDAY AS THE LOW PASSES TO
THE SOUTH. AS THE LOW DEEPENS...COLDER AIR WILL BE PULLED INTO THE
AREA...RESULTING IN THE CHANCE FOR SOME SNOW TO MIX IN WITH THE RAIN
ACROSS INLAND PORTIONS OF THE FORECAST AREA LATE SATURDAY AFTERNOON
AND SATURDAY EVENING. THERE IS THE CHANCE FOR A TRANSITION TO A
BRIEF PERIOD OF ALL SNOW BY SATURDAY EVENING...ESPECIALLY ALONG AND
NORTH OF THE HIGHWAY 84 CORRIDOR. THERE IS STILL CONSIDERABLE
UNCERTAINTY REGARDING HOW MUCH COLD AIR WILL BE IN PLACE PRIOR TO THE
SIGNIFICANT MOISTURE EXITING THE AREA...WHICH WILL DIRECTLY AFFECT
ANY POTENTIAL FOR ACCUMULATION. PLEASE STAY TUNED FOR FURTHER
UPDATES.

[MGC]

Remember how the models vacillated when forecasting the 2004 Gulf Coast Christmas snow? The same may be occurning with this system. Remember, the trend is your friend. Would be nice to see the low take shape a bit futher west and become deeper just south of Mobile, drawing down the cold air to meet the moisture. Most is not all snow events along the Gulf Coast were not forecast, lets hope that trend continues.......MGC