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4th Annual Fall/Winter Thread for the Mountains/Foothills


Met1985

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So far KGSP is not backing down and accumulations at mid day are mostly above 4500'. It remains to be seen if the next lobe in the moisture is more productive. The HRRR seems to have backed off some.

As of 3:25pm KGSP has not made their full Afternoon AFD available.

If the ECMWF Ensembles have it right, all 50 of them keep the NW NC High Country well below freezing through the 15th except for one day for a few hours.

Hopefully we can set up a general small snowpack early this week for the chance of a substantial snowstorm to follow.

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Blacksburg just took away my winter storm watch. 

Yep GSP just cancelled our winter storm watch for tomorrow through Thursday. The way this precip shield  is pin wheeling, we are getting our moisture coming in directly west and even southwest..not good..Maybe when the low moves off more to the east tomorrow we can get a good NWF

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It last update to the late afternoon AFD, KGSP points out several difficulties with the forecast that are highlighted in Red Below with the favorable factors in Green.

 

 

http://hp2.wright-weather.com/cgi-bin/text-awips.cgi?type=AFDGSP

 

 

NEAR TERM /THROUGH TUESDAY/...
AS OF 245 PM EST MONDAY...A BROAD UPPER LONGWAVE TROF CONTINUES TO
HIGHLIGHT THE PATTERN ALOFT...AND ALSO DRIVE THE WX AT THE SURFACE
WHERE A COLD FRONT CONTINUES TO SLIDE OUT OF THE NC FOOTHILLS
INTO/THROUGH THE NC/SC PIEDMONT AS WELL AS NORTHEAST GA. LIGHT
SHOWERS ASSOCIATED WITH SAID FRONT ARE HAVING A ROUGH GO AT IT WITH
SURFACE TD DEPRESSIONS UPWARDS OF 25-30 DEGREES THUS PROHIBITING
MUCH OF SAID PRECIP FROM REACHING THE SURFACE. THAT SAID...SURFACE
TEMPS WILL BEGIN TO COOL BEHIND THE FRONT ALLOWING FOR THAT GAP
TO NARROW AND THUS MOISTENING OF THE BOUNDARY LAYER WILL OCCUR.
LIKEWISE...A SERIES OF H5 VORTICITY MAXIMAS WILL PASS THROUGH
THE TROF BASE OVER THE NEXT 4-6 HOURS...WITH THE FIRST OF WHICH
DOING SO AT PRESENT TIME. THIS REGION OF UPPER SUPPORT CONTINUES
TO YIELD ENHANCED RA/SN SHOWERS OVER THE NC MOUNTAINS...WITH RA
SHOWERS BREAKING CONTAINMENT INTO THE FOOTHILLS AND UPPER PIEDMONT
LOCALES. THUS...POPS THROUGH THE REMAINDER OF THE AFTERNOON WILL
REMAIN AT CHANCE LEVELS OVER THE LOWER TERRAIN...INCREASING WITH
ELEVATION TOWARDS THE TN LINE WHERE CATEROGICALS ARE FAVORED.
POPS WILL THEN TAPER EVERYWHERE OUTSIDE OF THE MTNS INTO TUESDAY
MORNING AS THE FLOW VEERS GRADUALLY AND THE FIRST OF SAID H5 VORTS
EXITS TO THE EAST. POPS ALONG THE TN LINE WILL REMAIN ELEVATED AT
CATEGORICAL LEVELS AS FLOW BECOMES MORE ORTHOGONAL TO THE TERRAIN
THUS SETTING UP INCREASED UPSLOPE POTENTIAL...LASTING THROUGH THE
REMAINDER OF THE PERIOD.

AS FOR PRODUCTS...WILL CONTINUE TO WITH CURRENT WINTER STORM WARNING
ACROSS THE ALREADY WARNED LOCALES...EXTEND THE CURRENT ADVISORY
PRODUCT IN TIME THROUGH THE DAY TOMORROW...ALL THE WHILE EXPANDING
THE ADVISORY A BIT FURTHER SOUTH TO INCLUDE RABUN COUNTY GA GIVEN
LATEST HIGH ELEVATION SNOW TOTALS MEETING ADVISORY CRITERIA.
NEW SNOW TOTALS TOP OUT IN THE 2-4 INCH RANGE ALONG THE TN LINE
WITH A 1-3 INCHES POSSIBLE EASTWARD ALONG THE ESCARPMENT.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
AS OF 225 PM MONDAY...PROTRACTED NW FLOW SNOW EVENT WILL BE UNDERWAY
AT THE BEGINNING OF THE PERIOD...CONTINUING THROUGH AT LEAST WED
NIGHT BEFORE THE MOISTURE FINALLY BECOMES TOO SHALLOW TO SUPPORT
MUCH IN THE WAY OF SHOWER GENERATION. IN THE INTERIM...THE MOST
IMPRESSIVE ASPECT OF THIS EVENT WILL BE THE THERMODYNAMIC STRUCTURE
IN THE UPSLOPE LAYER...WITH TEMPS AS COLD AS -20 AT THE TOP OF THE
MOIST LAYER THROUGH MUCH OF THE PERIOD. TEMPS THIS COLD USUALLY
SUPPORT EFFICIENT SNOWFALL PRODUCING SHOWERS...WITH OFTEN OUTLANDISH
SNOW:LIQUID RATIOS IN THE NEIGHBORHOOD OF 30:1. HOWEVER...THE
QUESTION IS WHETHER THERE WILL BE ENOUGH LIQUID PRODUCED TO ACHIEVE
WARNING/WATCH CRITERIA SNOWFALL ON APPROPRIATE TIME AND SPATIAL
SCALES.


SOME OF THE OTHER INGREDIENTS THAT ONE TYPICALLY LIKES TO SEE FOR A
HEAVY NW FLOW SNOW EVENT ARE MISSING...INCLUDING THE ORIENTATION OF
THE FLOW. THE MAGNITUDE OF THE H8 FLOW ALMOST NEVER EXCEEDS 25 KTS
THROUGH THE PERIOD...WHILE THE DIRECTION REMAINS MOSTLY WNW.
THUS...THE ACTUAL COMPONENT OF THE FLOW ORTHOGONAL TO THE SOUTHERN
APPALACHIANS IS RELATIVELY WEAK. THE OTHER CONSEQUENCE OF THE
LESS-THAN-IDEAL FLOW ORIENTATION IS THAT LOW LEVEL TRAJECTORIES DO
NOT ORIGINATE FROM THE GREAT LAKES...WHICH IS TYPICALLY NEEDED TO
PRODUCE THE TYPE OF UPSTREAM STEEP LOW LEVEL LAPSE RATES/HIGH FROUDE
NUMBERS NECESSARY TO PRODUCE A LOT OF LIQUID EQUIVALENT
. INDEED...
THE SHORT TERM GUIDANCE DEPICTS THE BEST LOW LEVEL LAPSE
RATES/FROUDE NUMBERS UPSTREAM OF THE CENTRAL APPALACHIANS...WHILE
THEY ARE QUITE MODEST FROM CENTRAL KY THROUGH EAST TN. OVERALL...
THIS DOESN/T APPEAR TO BE A SETUP CONDUCIVE TO A WARNING-LEVEL
EVENT. HAVING SAID THAT...THERE ARE LOCATIONS ACROSS THE HIGH
ELEVATIONS OF THE SMOKIES AND OTHER HIGH PEAKS AND RIDGE TOPS ALONG
THE TN BORDER THAT WILL PROBABLY SEE STORM TOTALS OF MORE THAN A
FOOT THROUGHOUT THIS PROLONGED EVENT...BUT THESE AMOUNTS WOULD FALL
ON TIME/SPATIAL SCALES THAT DO NOT WARRANT A WARNING...BUT RATHER AN
ADVISORY.

OTHERWISE...IT WILL BE QUITE COLD THROUGH THE PERIOD...WITH TEMPS
AVERAGING A GOOD 15 DEGREES BELOW CLIMO. WIND CHILL VALUES WILL
REACH ADVISORY CRITERIA ACROSS THE HIGH ELEVATIONS OF WESTERN NC TUE
NIGHT...AND ACROSS ALL OF THE MOUNTAINS WED NIGHT. IN
FACT...LOCATIONS ABOVE 3500 FT MAY SEE WARNING CCRITERIA WIND CHILL
OF -15 OR LESS WED NIGHT.

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Wow. Just had a squall to come through that had the heaviest rates I've seen this year. It only lasted for maybe 10 minutes but had to drop at least a half inch. It's getting cold now too (24.4) so this stuff is sticking to everything. You can also tell the ratios are going up too. It's is getting real fluffy.

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