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000
FXUS61 KRNK 071217
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
717 AM EST SAT DEC 7 2013

.SYNOPSIS...
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ARCTIC HIGH PRESSURE WILL BUILD INTO THE AREA FROM THE NORTH TODAY
PROVIDING AN INFLUX OF COLD AIR THAT WILL INTERACT WITH
MOISTURE RETURNING NORTH BY SUNDAY. A COLD FRONT OVER THE
CAROLINAS WILL STALL OVER THE SOUTHEASTERN STATES TODAY...THEN
BECOME THE FOCUS FOR AN AREA OF LOW PRESSURE WHICH WILL DEVELOP
OVER THE SOUTHERN APPALACHIANS SUNDAY. THIS TROUGH OF LOW PRESSURE
WILL THEN TRY TO MOVE NORTH PUSHING ABUNDANT MOISTURE OVERTOP THE
AREA OF COLD HIGH PRESSURE. SIGNIFICANT WINTRY PRECIPITATION WILL
BE THE RESULT.

WINTER STORM WARNINGS/FREEZING RAIN ADVISORIES ARE IN EFFECT
FOR MUCH OF THE REGION SUNDAY.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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AS OF 500 AM EST SATURDAY...

NO SHORTS OR T-SHIRTS TO BE FOUND TODAY AS BEACH LIKE AIRMASS HAS
NOW BEEN PUSHED SOUTH OF THE FORECAST AREA...SUPPRESSED BY A LARGE
EXPANDING AREA OF HIGH PRESSURE. VERY COLD 1040+ MB SFC HIGH
PRESSURE EXTENDS FROM THE PLAINS STATES TO THE OHIO VALLEY AND
GREAT LAKES REGION. THIS HIGH WILL GRADUALLY NOSE ITS WAY ACROSS
THE APPALACHIANS TODAY...COLD AIR ADVECTION PUTTING A DRAG ON ANY
SORT OF TEMPERATURE RISE. THIS WILL BE A BIG CONTRAST TO
YESTERDAY...A CHANGE OF ABOUT 30 DEGREES. DANVILLE HIT 78 DEGREES
YESTERDAY. TODAY THEY WILL BE LUCKY TO HIT 48. FOR THE MOST
PART...THE NUMBER YOU SEE ON YOUR THERMOMETER THIS MORNING WILL
THE NUMBER IT WILL REFLECT FOR MOST OF THE DAY...SOMETHING MOST
LIKELY BEGINNING WITH A 3 OR 4.

RAIN ASSOCIATED WITH THE SURFACE FRONT WILL CONTINUE TO PROGRESS
SOUTH AND EAST AND AWAY FROM THE FORECAST AREA. AREAS ALONG AND
EAST OF THE BLUE RIDGE SHOULD EXPERIENCE SOME PARTIAL CLEARING BY
AFTERNOON. A BIT MORE CLOUDINESS MAY LINGER IN THE MOUNTAINS WEST
OF THE BLUE RIDGE...AND CAN`T RULE OUT SOME FLURRIES OR DRIZZLE
OVER THE WV/VA HIGHLANDS.

BOTTOM LINE...THE DAY AS A WHOLE LOOKS DRY...TEMPERATURES BACK TO
THE SEASONAL NORM...MORE DECEMBER LIKE.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY NIGHT/...
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AS OF 530 AM EST SATURDAY...

MODEL FORECASTS REMAIN ON TRACK FOR SIGNIFICANT WINTRY
PRECIPITATION SUNDAY. WINTER STORM WARNINGS ARE IN EFFECT FOR THE
MAJORITY OF OUR COUNTY WARNING AREA...38 OF THE 40 COUNTIES.

ONLY SUBTLE CHANGES HAVE BEEN MADE TO THE GRIDDED FORECASTS.
THIS YIELDS CONSISTENCY TO WHAT WE HAVE BEEN ADVERTISING THE LAST
SEVERAL DAYS. COMPUTER WORDED FORECASTS SHOULD LOOK VERY SIMILAR
TO WHAT THE DID YESTERDAY... THE ONLY DIFFERENCE IS WE ARE NOW ONE
DAY CLOSER TO THE EVENT.

FORECAST MODELS LOOK VERY MUCH THE SAME WITH FULL LATITUDE LONG
WAVE TROUGH AXIS OVER THE CENTRAL AND WESTERN CONUS...AND A LARGE
ARCTIC SURFACE HIGH MORPHING ITS WAY EAST AIDED BY STRONG
CONFLUENT FLOW ALOFT IN THE NORTHEASTERN PART OF THE UPPER TROUGH.
LOW LEVEL BAROCLINIC ZONE WHICH HAS BEEN SUPPRESSED TO THE GULF
COAST AND SOUTHEAST STATES WILL NOW BECOME THE FOCUS FOR THE NEXT
ROUND OF PRECIPITATION AS SHORTWAVE ENERGY ROUNDS THE BASE OF THE
UPPER TROUGH RESULTING IN A WAVE OF LOW PRESSURE TO FORM ALONG THE
BAROCLINIC ZONE AND RIPPLE NORTHEAST ACROSS THE SOUTHERN
APPALACHIANS SUNDAY. THIS WILL CAST DEEPER MOISTURE NORTHEAST AND
OVERTOP THE COLD DOME OF HIGH PRESSURE. RESULT WILL BE WIDESPREAD
OVERRUNNING PRECIPITATION.

PRECIPITATION IS EXPECTED TO OVERSPREAD THE AREA FROM SOUTH TO
NORTH BEGINNING LATE TONIGHT...EARLY SUNDAY MORNING. FORECAST
SOUNDINGS SUGGEST MOST AREAS WILL PARTAKE IN FREEZING RAIN.
THE EXCEPTION WILL BE THE VIRGINIAS NORTHWARD WHERE THE LOW LEVEL
T/TD PROFILE WILL BE SUCH THAT A MIX OF SLEET AND SNOW MAY OCCUR
FOR A FEW HOURS AT THE ONSET. THINK AREAS NORTH OF HIGHWAY 460
COULD SEE AN INCH OR TWO OF SNOW/SLEET BEFORE THE CHANGE OVER TO
FREEZING RAIN SUNDAY...WITH ONLY TRACE AMOUNTS OF SOLID
PRECIPITATION SOUTH OF HWY 460...AND ALL FREEZING RAIN FROM THE
NORTH CAROLINA BORDER SOUTHWARD.

DURING THE DAY SUNDAY...THE STRENGTH OF THE WARM NOSE ALOFT
INCREASES TO AS MUCH AS +6 TO +7 DEG C ACROSS THE AREA...WHILE
MOST OF THE REGION AT THE SURFACE REMAINS AT OR BELOW FREEZING.
WITH HIGH PRESSURE CENTERED TO OUR NORTH...IT WILL CONTINUE TO
REINFORCE THE BOUNDARY LAYER WITH SUBFREEZING AIR COURTESY OF A
PERSISTENT NORTHEAST GEOSTROPHIC WIND. THIS CLASSIC COLD AIR
DAMMING SET-UP WILL HELP MAINTAIN POTENTIAL FOR FREEZING RAIN
OVER MOST OF THE AREA THROUGH SUNDAY NIGHT. WARMING ALOFT WILL
EVENTUALLY MIX TO THE SURFACE...EFFECTING AREAS WEST OF THE
APPALACHIAN DIVIDE FIRST...THEN WORKING TO MODIFY THE AIRMASS EAST
OF THE DIVIDE SLOWLY WITH TIME. SOME AREAS...ESP FROM HWY 460
NORTHWARD MAY NOT SEE TEMPS CLIMB ABOVE 32 UNTIL DAYBREAK MONDAY.

SINCE THE TEMPERATURE AT THE SURFACE SEEMS LIKE IT WILL REMAIN AOB
FREEZING FOR AN EXTENDED PERIOD OF TIME...THE NUMBER TO REALLY WATCH
WILL BE THE QPF. MODELS ARE NOT AS CONSISTENT ON HOW MUCH LIQUID
EQUIVALENT WILL ACTUALLY OCCUR...BUT FOR THE MOST PART THE NUMBER
IS ABOVE A QUARTER OF AN INCH ON THE AVERAGE...WITH UPWARDS OF A
HALF TO MAYBE THREE QUARTERS OF AN INCH ALONG THE SPINE OF THE
APPALACHIANS WHERE EASTERLY AGEOSTROPHIC UPSLOPE FLOW WILL AID IN
PRECIP PRODUCTION. THAT SAID...HAVE FOCUSED THE AREA OF THE
HEAVIEST ICE ACCRETIONS ALONG THE SPINE OF THE BLUE RIDGE WITH
UPWARDS OF A HALF INCH /0.50/ OF ICE ACCUMULATION FROM FLOYD
COUNTY VA NORTHEASTWARD INTO THE VA HIGHLANDS AND SOUTHERN
SHENANDOAH VALLEY. FARTHER EAST AND WEST AWAY FROM THE BLUE RIDGE
TAPERED THE AMOUNTS BACK TO ABOUT A QUARTER OF AN INCH /0.25/.
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&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
AS OF 255 PM EST FRIDAY...

WEDGE SHOULD BE CONTINUING TO WEAKEN BY EARLY MONDAY WITH ONGOING
STRONG 85H WARM ADVECTION SLOWLY CAUSING THE COLD POOL TO FADE WITH
TIME DURING THE DAY AS THE COLD FRONT TO THE WEST APPROACHES. BASED
ON LATEST MODEL SOUNDINGS AND IDEA THAT THE WEDGE WILL BE SLOW TO
EXIT UNTIL A FEW HOURS AFTER SUNRISE...WILL KEEP IN SOME LIGHT
FREEZING RAIN MENTION MAINLY GREENBRIER INTO THE HIGHLANDS EARLY ON.
OTRW RETURNING DEEPER BAND OF MOISTURE SHOULD BE CROSSING THE WEST
THRU MIDDAY MONDAY AND THEN LIKELY WEAKENING ALONG THE BLUE RIDGE BY
EARLY AFTERNOON AS WEAK ENERGY SHEARS BY TO THE NE. HOWEVER AS THE
BOUNDARY SLOWS AGAIN HEADING EAST MAY SEE YET ANOTHER IMPULSE RIDE
UP THRU THE CAROLINAS RESULTING IN ANOTHER ROUND OF RAIN SE LATE.
WILL HAVE BASICALLY ALL LIQUID DURING THE AFTERNOON AS SURFACE TEMPS
WARM ENOUGH TO PUSH MOST INTO THE 40S IF NOT 50S SE.

FRONT PUSHES OUT TO THE BLUE RIDGE MONDAY NIGHT BEFORE SEEING
ANOTHER WAVE ALONG THE BOUNDARY WHICH MAY RESULT IN ANOTHER SWATH OF
PRECIP RIDING UP THE BAROCLINIC ZONE BACK TO THE MOUNTAINS BY EARLY
TUESDAY. HOWEVER WESTWARD EXTENT REMAINS TRICKY ALONG WITH TEMPS AS
MOST GUIDANCE SHOWING VALUES COLD ENOUGH ALOFT FOR SNOW FAR WEST BY
EARLY TUESDAY WITH MOSTLY RAIN ELSW UNTIL THE 85H 0C LINE SWINGS
EAST DURING THE DAY WHEN THE BOUNDARY LAYER MAY BE TOO WARM ESPCLY
EAST. THUS RUNNING WITH MAINLY CHANCE POPS MONDAY NIGHT BUT HIGHER
SE AND THEN A GRADUAL NW TO SE DECREASE IN COVERAGE TUESDAY WITH -SN
NW LATER MONDAY NIGHT/EARLY TUESDAY AND A MIX BLUE RIDGE TO JUST
RAIN EAST FOR NOW. SHOULD FINALLY RETURN TO DRY BUT VERY CHILLY
WEATHER FOR THE REST OF THE WEEK AS STRONG HIGH PRESSURE BUILDS EAST
REACHING THE COAST ON FRIDAY. THIS WILL KEEP TEMPS WELL BELOW NORMAL
WITH MOST HIGHS IN THE 30S FOR MUCH OF THE REST OF THE WEEK.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
AS OF 1200 AM EST SATURDAY...

POOR AVIATION CONDITIONS EXPECTED THROUGH THE FIRST 8-10 HOURS OF
THE TAF...THEN SOME IMPROVEMENTS THROUGH THE REMAINDER OF THE TAF
VALID PERIOD. AN ARCTIC FRONT WAS CREEPING INTO SW VA...BUT MAKING
BETTER PROGRESS AS A BACKDOOR COLD FRONT SOUTHWARD THROUGH THE
PIEDMONT AS ARCTIC HIGH PRESSURE BUILDS EASTWARD NORTH OF 40 DEG
LAT. OVERNIGHT...THE COLD AIR WILL CONTINUE TO FILTER IN FROM THE
WEST AND NORTH AND SHOULD FILTER THROUGH MOST OF THE CWA IN ONE
DIRECTION OR ANOTHER BY DAYBREAK...BUT MOSTLY IT APPEARS FROM THE
NORTH. RAIN...IMMEDIATELY BEHIND THE FRONTAL BOUNDARY...WILL
CONTINUE PROGRESSING THROUGH THE PIEDMONT...AND MOST PCPN AFT 08Z
WILL BE IN THE FORM OF -DZ. TEMPS SHOULD REMAIN ABOVE FREEZING
THROUGH 12Z IN MOST AREAS...SO HAVE REMOVED ANY MENTION OF FROZEN
PCPN WITH THIS TAF SET. EXPECT MOSTLY MVFR-IFR CIGS
OVERNIGHT...WITH LOCALIZED POCKETS OF IFR CIGS...ESPECIALLY AT
BLF. VSBYS MOSTLY MVFR IN -RA AND DZ...WITH ISOLATED POCKETS OF
IFR...POSSIBLY LIFR AT BLF IF CIGS DROP BELOW 004. WINDS...NW-NE
THROUGH THE CWA AT SPEEDS OF 7-10KTS WITH LOW END GUSTS ACROSS THE
PIEDMONT OVERNIGHT AS COLD AIR SURGES DOWN FROM THE NE. AFT 18Z
SAT...EXPECT IMPROVEMENT OF CIGS AT BCB/ROA/DAN AT WORST...WITH
LYH/LWB/BLF POTENTIALLY REMAINING IFR TO LOW END MVFR THROUGH MUCH
OF THE DAY. CLOUDS WILL LOWER AFT 06Z AND WINTER PCPN WILL ALSO BE
AFTER THIS TAF VALID PERIOD.

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


EXTENDED AVIATION...

AFTER THE BRIEF BREAK IN THE POOR WEATHER ON SATURDAY...WE GET
RIGHT BACK INTO POOR CONDITIONS AS HIGH PRESSURE MOVES IN TO A
WEDGE POSITION AND OVERRUNNING LEADS TO LOW CIGS AND MIXED PCPN
FROM S TO N SATURDAY NIGHT...THEN CONTINUING ON SUNDAY. TEMPS
SHOULD MODERATE ENOUGH TO END THE WINTRY PCPN BY MONDAY...BUT WE
WILL STAY WITH PCPN AND LOW CLOUDS/VSBYS RIGHT INTO TUESDAY. HIGH
PRESSURE FINALLY BUILDS IN LATER ON TUESDAY WITH A RETURN TO VFR
FOR THE MIDDLE OF THE WEEK.

&&


.RNK WATCHES/WARNINGS/ADVISORIES...
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VA...WINTER STORM WARNING FROM 4 AM SUNDAY TO 9 AM EST MONDAY FOR
     VAZ011-013-014-017>020-022>024-033>035-045>047.
     WINTER STORM WARNING FROM 4 AM SUNDAY TO MIDNIGHT EST SUNDAY
     NIGHT FOR VAZ010-012-015-016.
     WINTER STORM WARNING FROM 4 AM SUNDAY TO 4 AM EST MONDAY FOR
     VAZ032-043-044-058-059.
     FREEZING RAIN ADVISORY FROM 4 AM SUNDAY TO MIDNIGHT EST SUNDAY
     NIGHT FOR VAZ007-009.
NC...WINTER STORM WARNING FROM 4 AM SUNDAY TO MIDNIGHT EST SUNDAY
     NIGHT FOR NCZ001-002-018.
     WINTER STORM WARNING FROM 4 AM SUNDAY TO 4 AM EST MONDAY FOR
     NCZ003>006-019-020.
WV...WINTER STORM WARNING FROM 4 AM SUNDAY TO 9 AM EST MONDAY FOR
     WVZ043>045.
     WINTER STORM WARNING FROM 4 AM SUNDAY TO MIDNIGHT EST SUNDAY
     NIGHT FOR WVZ042.
-- End Changed Discussion --

&&

$$
SYNOPSIS...PM
NEAR TERM...PM
SHORT TERM...PM
LONG TERM...JH
AVIATION...MBS/RAB