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000
FXUS61 KRNK 110003
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
703 PM EST TUE DEC 10 2013

.SYNOPSIS...
HIGH PRESSURE WAS ENTERING THE TENNESSEE VALLEY THIS EVENING AND
WILL BE CENTERED OVER THE SOUTHERN APPALACHIANS BY MORNING. A COLD
FRONT WILL CROSS THROUGH THE AREA WEDNESDAY EVENING. A MORE
COMPLEX STORM SYSTEM WILL MOVE FROM THE CENTRAL PLAINS ON FRIDAY
INTO THE EASTERN UNITED STATES BY SATURDAY NIGHT.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 700 PM EST TUESDAY...

DECREASED THE CLOUD COVER AS IR SATELLITE AND SURFACE OBS CONFIRM
THAT AREA IS CLEARING OUT A COUPLE HOURS QUICKER THAN ANTICIPATED.
WILL CONTINUE TO HANG ON TO CLOUD COVER ACROSS WESTERN GREENBRIER
THROUGH ALMOST DAYBREAK WEDNESDAY.

AS OF 335 PM EST TUESDAY...

NO ECHOS ON THE RADAR AT 20Z/3PM AND NO OBSERVATIONS REPORTING
ANY SNOW. EVEN THE LOW LEVEL MOISTURE IN THE WESTERN UPSLOPE AREAS
OF SOUTHWEST VIRGINIA WILL ERODE ENOUGH TO HAVE CLOUDS CLEAR OUT
AFTER THIS EVENING.

AT THE SURFACE HIGH PRESSURE WAS MOVING INTO THE TENNESSEE VALLEY
AND WILL BE CENTERED OVER THE FORECAST AREA BY MORNING. WINDS JUST
ABOVE THE SURFACE INCREASE TO AROUND 50 KNOTS THIS EVENING ALONG
THE BLUE RIDGE. BUFKIT WAS SHOWING THE INVERSION DROPPING TO NEAR
RIDGE TOP LEVEL AROUND BOONE WITH MOMENTUM TRANSFER AROUND 40
KNOTS. HAVE LEFT WIND ADVISORY IN PLACE THROUGH MIDNIGHT. WINDS
WILL DIMINISH AS THE HIGH GETS CLOSER LATE TONIGHT.

THE LOWEST 850 MB TEMPERATURES PASS THROUGH THE AREA TONIGHT AND
ARE SLOWLY MODERATING LATE TONIGHT AND WEDNESDAY. TEMPERATURES
ALREADY DOWN IN THE LOWER TO MID 20S AT THE HIGHEST ELEVATIONS IN
THE WEST...GRANDFATHER MOUNTAIN WAS AT 20 DEGREES AT 3PM AND
GRAYSON HIGHLANDS STATE PARK WAS 26. HAVE LOWERED MINIMUM
TEMPERATURES ON THE RIDGES AND IN WESTERN GREENBRIER AND SUMMERS
COUNTIES WERE THERE IS FRESH SNOW ON THE GROUND. KEPT MAXIMUM
TEMPERATURES JUST BELOW MAV GUIDANCE VALUES FOR WEDNESDAY.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/...
AS OF 400 PM EST TUESDAY...

CORE OF COLDEST H85 AIR ARRIVES ACROSS THE OHIO VALLEY WITH A
MOISTURE STARVED SHORTWAVE WEDNESDAY NIGHT. CRASHING INVERSION
SHOULD SQUEEZE WINDS CLOSER TO THE SURFACE...ALLOWING CHANNELING
WITH NW WINDS...SUCH THAT SOME 35KT GUSTS ARE POSSIBLE ALONG THE
HIGHEST SLOPES WITH 25KT GUSTS AT LOWER ELEVATIONS. SCANT MOISTURE
MAY BE ENOUGH FOR A QUICK SHOT FOR UPSLOPE SNOW SHOWERS ACROSS
WESTERN GREENBRIER JUST BEFORE MIDNIGHT. CLOUDS AND WIND SHOULD KEEP
TEMPS UP A BIT AT LEWISBURG DESPITE THE SHALLOW ARCTIC AIRMASS. LESS
WINDS AND CLOUDS THROUGH THE PIEDMONT AND SOUTHSIDE WILL ALLOW TEMPS
TO FALL INTO THE LOW TO MID 20S.

ANY CLOUDS LEFT OVER GREENBRIER THURSDAY MORNING SHOULD DISSIPATE
RATHER QUICKLY WITH HIGH PRESSURE NEARBY...AND THE UPPER TROUGH
SLOWLY LIFTING NORTHEAST WHICH ALLOWS WAA TO ENSUE.
REGARDLESS...TEMPS WILL STRUGGLE INTO THE MID AND UPPER 30S AT MOST
CITIES. VERY DRY AIR IN PLACE WITH SURFACE HIGH JUST TO OUR
SOUTHEAST SHOULD ALLOW FOR DECOUPLING AND A VERY COLD NIGHT WITH
LOWS POTENTIALLY BELOW GUIDANCE.

H85 TEMPS WARM JUST ABOVE 0C FOR THE SOUTHERN HALF OF THE REGION AS
TEMPS TRY TO RECOVER FROM THE MORNING TEENS FOR MANY LOCATIONS.
APPEARS AS THOUGH THICK HIGH CLOUDS MAY HOLD OFF UNTIL LATE
DAY...HOWEVER IF THEY ARRIVE FASTER MAX TEMPS COULD BE MORE IN THE
UPPER 30S LOWER 40S FOR FRIDAY. THIS WOULD HAVE IMPLICATIONS ON LOW
PRESSURE DEVELOPING THROUGH THE GULF COAST STATES FOR FRIDAY NIGHT.

AT THE SURFACE...THE ECMWF/GFS LOOK FAIRLY SIMILAR...BUT THAT`S
WHERE THE SIMILARITIES END LATE FRIDAY NIGHT. THE ECMWF IS MUCH
COLDER AND ALLOWS FOR COLD AIR DAMMING TO OCCUR MUCH MORE QUICKLY
THAN THE GFS. ALSO THE ECMWF WOULD INDICATE AN ISOTHERMAL NEAR
FREEZING SOUNDING...WHICH WOULD SUGGEST RAIN TO START...THEN QUICK
WETBULBING AND SNOW AFTERWARDS. ALTHOUGH THE ECMWF IS MUCH SLOWER
THAN THE GFS WITH THE BEGINNING OF THE PRECIP...QPF USUALLY BREAKS
OUT MUCH QUICKER IN ISENTROPIC LIFT SO WILL CONTINUE TREND OF AN
EARLIER ONSET THAN WHAT MODELS SUGGEST. SINCE WPC IS FAVORING THE
ECMWF...WILL FOLLOW ITS THERMAL PROFILE AND GO WITH A RAIN TO
RAIN/SNOW TO SNOW SCENARIO FOR NOW. HOWEVER...THIS EVENT IS FAR OFF
AND THERE STILL WILL BE SOME CHANGES NECESSARY AS THE MODELS GET A
BETTER HOLD ON THE ARCTIC HIGH COMING ACROSS THE GREAT LAKES NEXT
WEEK. WE SAW THIS HAPPEN WITH OUR MOST RECENT EVENT...ESPECIALLY THE
GFS...WHICH WAS CONSISTENTLY WARM A FEW DAYS AWAY BEFORE SWINGING
BACK TO A COLDER SOLUTION WITHIN 48 HOURS OF THE EVENT.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 300 PM EST TUESDAY...

ON SATURDAY...WE ARE ANTICIPATING AN UPPER LOW/TROUGH TO BE MOVING
THROUGH THE MID-MISSISSIPPI VALLEY. A SHORTWAVE TROUGH ALONG THE
SOUTHERN JET WILL GET EJECTED NORTHEAST IN ADVANCE OF THE UPPER
LOW/TROUGH. MODEL GUIDANCE STILL VARIES ON BOTH THE TIMING AND TRACK
OF BOTH THE PARENT SYSTEM AND THE ASSOCIATED LEADING SHORTWAVE
TROUGH AND THEIR DEGREE OF INTERACTION ACROSS OUR REGION. CLOSER TO
THE SURFACE...A RIDGE OF HIGH PRESSURE WILL BE ALONG THE LEE OF THE
APPALACHIANS ALONG WITH MANY AREAS BELOW FREEZING SATURDAY MORNING
AS THE PRECIPITATION IS ARRIVING.

A QUICK GLANCE AT ALL THE SOLUTIONS FOR THE WEEKEND SUGGESTS THAT
WINTRY PRECIPITATION OF SOME FORM WILL IMPACT AT LEAST PARTS OF THE
REGION. MODEL SOLUTIONS FROM YESTERDAY WERE LEANING TOWARD ENOUGH OF
A WARM NOSE FOR A WINTRY MIX OF PRECIPITATION FOR THE AREA UNTIL
SUCH POINT WHERE THE REGION WAS ON THE BACKSIDE OF THE PARENT UPPER
LOW. AT THIS POINT...STRONG NORTHWEST FLOW AND COLD AIR ADVECTION
WOULD YIELD UPSLOPE SNOW SHOWERS IN THE MOUNTAINS TO CONCLUDE THE
EVENT. WHILE THE LATTER HALF OF THIS SCENARIO IS STILL LOOKING
PROMISING LATE SATURDAY NIGHT THROUGH SUNDAY NIGHT...THE EARLIER
PART WILL BE REVAMPED A BIT.

THE BIGGEST ADJUSTMENTS WILL BE IN THE SATURDAY PORTION OF THE
FORECAST. ENOUGH WET BULB COOLING IS EXPECTED TO TAKE PLACE SUCH
THAT THE LOW LEVEL T/TD PROFILE FALLS BELOW 0 C FOR MUCH OF THE AREA
ALONG THE HIGH PRESSURE RIDGE AXIS. ALSO...WITH THE WET-BULBED
COOLED AIR...FORECAST HIGH TEMPERATURES ON SATURDAY ALSO SHOULD BE
COOLER THAN PREVIOUSLY ADVERTISED. THE RESULT WILL BE A SNOW VERSUS
RAIN FORECAST FOR SATURDAY. THE BULK OF THE SNOW WILL BE EARLY IN
THE DAY. STRONG SOUTHWEST FLOW WARM AIR ADVECTION WILL GRADUALLY WIN
OUT OVER THE WET-BULB COOLING THAT TOOK PLACE BECAUSE OF THE
PRECIPITATION. MOST OF THE REGION WILL BE IN THE MID TO UPPER 30S BY
SATURDAY AFTERNOON...AND WE WILL BE LOOKING FOR EITHER A COLD RAIN
OR A WHITE RAIN TO BE OCCURRING BY THE AFTERNOON FOR MOST OF THE
REGION.

SUNDAY NIGHT NIGHT INTO MONDAY...LOOK FOR GUSTY CONDITIONS ACROSS
THE REGION AS A TIGHT PRESSURE GRADIENT FORMS BETWEEN THE DEPARTING
SYSTEM AND AN APPROACHING REGION OF HIGH PRESSURE. FORECAST GUIDANCE
OFFERS 850 MB NORTHWEST WINDS ANYWHERE BETWEEN 35 AND 50 KTS DURING
THE TIME PERIOD. THIS SHOULD HELP MAINTAIN UPSLOPE SNOW SHOWERS IN
THE PREFERRED AREAS OF SOUTHEAST WEST VIRGINIA SOUTH INTO THE
NORTHERN MOUNTAINS OF NORTH CAROLINA. HOWEVER...WITH DRIER AIR
ARRIVING...THERE WILL BE A GRADUAL TREND TOWARD DECREASING COVERAGE.
SURFACE WINDS IN THE MOUNTAINS WILL BE STRONG...POSSIBLY AT LEAST
WIND ADVISORY LEVELS.

MONDAY INTO TUESDAY...COLD SURFACE HIGH PRESSURE WILL BUILD OVER AND
THEN EAST OF THE REGION. THERE LIKELY WILL BE INCREASING CLOUD COVER
AND WIND SPEEDS ON TUESDAY...ESPECIALLY IN THE WEST...AS A SHORTWAVE
TROUGH IS PROGGED TO SWING THROUGH THE GREAT LAKES REGION.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
AS OF 645 PM EST TUESDAY...

MUCH IMPROVED AVIATION CONDITIONS EXPECTED THIS TAF VALID PERIOD
COMPARED TO ANY RECENT DAYS. ALL SITES SHOULD SEE VFR CIGS AND
VSBYS THROUGH THE TAF VALID PERIOD. UPSLOPE SC CURRENTLY
DISSIPATING ACROSS EASTERN WV...AND REMAINING MOSTLY JUST WEST OF
LWB AND BLF. REMAINING SC SHOULD REMAIN NEAR THE HIGHER ELEVATIONS
OF THE ALLEGHANYS AND AT BEST SKIRT LWB/BLF WITH SCT 025-030 CIGS
OVERNIGHT. ELSEWHERE...DOWNSLOPE WINDS AND DIMINISHING CAA
RESULTING IN CLR/SKC. WINDS ARE ALSO DIMINISHING AND BACKING MORE
TOWARD THE WEST. WINDS WED SHOULD BE SW 5-8KTS WITH LOW END GUSTS
TO 16KTS BLF/ROA.

HIGH CONFIDENCE IN CIGS AND VSBYS THROUGH TAF VALID PERIOD.
HIGH CONFIDENCE IN WIND DIR/SPD THROUGH TAF VALID PERIOD.

EXTENDED AVIATION DISCUSSION...
THE NEXT ORGANIZED STORM SYSTEM WILL MOVE INTO THE REGION ON
SATURDAY INTO SUNDAY. RAIN AND SNOW ARE POSSIBLE WITH THIS SYSTEM
WITH IFR TO MVFR CEILINGS AND VISIBILITIES.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR NCZ001-002-018.
WV...NONE.

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS/CF
SHORT TERM...KM
LONG TERM...DS
AVIATION...AMS/RAB