-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KRNK 081055
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
555 AM EST SUN DEC 8 2013

.SYNOPSIS...
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ARCTIC HIGH PRESSURE TO OUR NORTH WILL PROVIDE A CONTINUOUS
SOURCE OF COLD AIR TODAY. A TROUGH OF LOW PRESSURE DEVELOPING
OVER THE TENNESSEE RIVER VALLEY WILL PROVIDE A CONTINUOUS
SOURCE OF MOISTURE. THE COLD AIR WILL INTERACT WITH MOISTURE
FOR A BLEND OF WINTRY PRECIPITATION ACROSS THE REGION TODAY
AND TONIGHT. FREEZING RAIN WILL BE THE DOMINANT PRECIPITATION
TYPE.
-- End Changed Discussion --

&&

.NEAR TERM /THROUGH TONIGHT/...
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AS OF 500 AM EST SUNDAY...

ALL INGREDIENTS ARE IN PLACE FOR WINTRY PRECIPITATION TODAY.
SURFACE HIGH PRESSURE IS STILL BUILDING INTO THE AREA FROM THE
NORTHEAST. THIS WILL PROVIDE A CONTINUOUS SOURCE OF COLD AIR
TODAY...TEMPERATURES CONTINUING TO FALL THROUGH THE MORNING HOURS.
MOST LOCATIONS SHOULD WETBULB AT OR BELOW FREEZING THIS MORNING.
SOME AREAS ARE ALREADY WELL BELOW FREEZING...NOTING THE 21 DEG F
TEMP AT HSP AIRPORT AS OF 5AM.

TROUGH OF LOW PRESSURE OVER THE TENNESSEE RIVER VALLEY WILL
STRENGTHEN TODAY...PROVIDING A CONTINUOUS SOURCE OF MOISTURE.
ALL MODELS INDICATE STRONG ISENTROPIC LIFT ACROSS THE AREA WITH
INCREASING MID LEVEL FRONTOGENESIS. THIS SHOULD YIELD WIDESPREAD
DEVELOPMENT OF PRECIPITATION...QPF OF A QUARTER TO THREE QUARTERS
OF AN INCH...FROM 12Z/7AM THIS MORNING THROUGH 12Z/7AM MONDAY
MORNING. THIS WILL TRANSLATE INTO AN ACCUMULATION OF SIGNIFICANT
WINTRY PRECIPITATION...THE DOMINANT P-TYPE...FREEZING RAIN.

WARM INTRUSION ALOFT CAPS THE COLD BOUNDARY LAYER. VERY WARM
AIR...4-8 DEG C...IS MOVING NORTHEAST THROUGH THE TENNESSEE VALLEY
AND WILL FLOW UP AND OVERTOP THE COLD AIR WEDGE HERE ON THE EAST
SIDE OF THE APPALACHIAN MOUNTAINS. THIS SHOULD ENSURE THAT
MOST... IF NOT ALL...HYDROMETEORS MELT ON THERE WAY TO THE
SURFACE. THE ONLY AREA WHERE THE SOUNDING PROFILE MAY ENTERTAIN
ISOTHERMAL CHARACTERISTICS...THE WARM NOSE CLOSER TO 0 DEG C...IS
FROM THE HIGHLANDS OF VA/WV NORTHEASTWARD INTO THE SHENANDOAH
VALLEY. AS SUCH...THE PRECIPITATION MAY TAKE ON THE FORM OF SLEET
AND SNOW WHICH COULD ACCUMULATE AN INCH OR TWO THIS MORNING. BY
AFTERNOON...THE WARM INTRUSION SHOULD MAKE ITS WAY FAR ENOUGH
NORTH LATITUDE TO CHANGE THE PRECIP TO FREEZING RAIN THERE TOO.

THE WEDGE OF COLD AIR ON THE EAST SIDE OF THE MOUNTAINS WILL
LIKELY REMAIN IN PLACE THROUGH TONIGHT. GIVEN THE EXTENT OF
WARMING WHICH IS FORECAST TO TAKE PLACE ALOFT...SOME OF THE MODELS
INDICATING AS WARM AS +10 DEG C AT 85H...MODIFICATION OF THE COLD
BOUNDARY LAYER SEEMS INEVITABLE...AND SHOULD RESULTING IN
STEADILY RISING TEMPERATURES AT THE SURFACE. A GRADUAL CHANGE FROM
FREEZING RAIN TO JUST PLAIN OL RAIN IS ANTICIPATED...ESP WEST OF
THE APPALACHIAN DIVIDE. WITH THE INCREASED WARMING ALOFT...FOG
WILL LIKELY BECOME AN ISSUE AS THE WARMER AIR MIXES WITH THE COLD
MOIST BOUNDARY LAYER.

GREATEST ACCUMULATIONS OF ICE TODAY/TONIGHT ARE EXPECTED ALONG
THE SPINE OF THE BLUE RIDGE WHICH WILL RESIDE IN THE COLDER AIR
THE LONGEST...AND WHERE THE LOW LEVEL UPSLOPE EASTERLY WIND FLOW
WILL ENHANCE THE LOCAL QPF/ICING AMOUNTS. HIGHEST IMPACT FROM THIS
EVENT WILL BE ICING ON ELEVATED SURFACES. THE GROUND IS STILL
RELATIVELY WARM FROM THIS PAST WEEKS WARMTH...SO THEORETICALLY
THERE SHOULD BE LESS OF AN IMPACT TO ROAD SURFACES. THAT BEING
SAID...ITS STILL A GOOD DAY TO SIT THIS ONE OUT. THE ROADS CAN
FOOL YOU ONCE THE AIR TEMP REMAINS BELOW FREEZING LONG ENOUGH.
UNTREATED SURFACES MAY LOOK WET...BUT MAY ACTUALLY CONTAIN A THIN
COATING OF ICE HIDDEN BY WHAT APPEARS TO BE JUST WET PAVEMENT. IF
VENTURING OUT OF DOORS...PREP ACCORDINGLY. A COLD RAIN OR FREEZING
RAIN MAKES FOR IDEAL HYPOTHERMIC CONDITIONS. WALKING OUT TO CHECK
THE ICE ACCUMULATION ON MY VEHICLE WAS ENOUGH TO MAKE MY TEETH
CHATTER...AS THE OLD SAYING GOES...THE DAMPNESS IN THE AIR WILL
CUT RIGHT THROUGH YA...A COLD RAW RAIN.
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&&

.SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/...
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AS OF 500 AM EST SUNDAY...

FOR THE MONDAY MORNING COMMUTE...MAY SEE A FEW POCKETS OF FREEZING
RAIN LEFT OVER ACROSS THE SHENANDOAH VALLEY...BUT OTHERWISE EXPECT
TEMPERATURES TO BE WARM ENOUGH ALL OTHER LOCATIONS FOR PRECIPITATION
TO FALL AS LIQUID. ANY ICING LEFTOVER FROM THE OVERNIGHT SHOULD MELT
QUICKLY DURING LATE MORNING AS TEMPERATURES CLIMB INTO THE MID 40S
NORTH OF INTERSTATE 81...AND INTO THE LOW 50S FURTHER SOUTH. DURING
MID AFTERNOON...EXPECT RAIN TO BECOME MORE SHOWERY IN NATURE AS A
COLD FRONT MAKES ITS WAY EAST ACROSS THE AREA. AS WINDS SHIFT
NORTHWESTERLY BEHIND THE FRONT...WILL SEE SHOWERS DIMINISH IN
COVERAGE FOR THE EVENING...ALTHOUGH THE BREAK WILL BE SHORT-LIVED.

PACIFIC HIGH PRESSURE WILL BUILD IN BEHIND THE COLD FRONT MONDAY
NIGHT...AND WILL BUILD SOUTHWARD AGAINST THE EASTERN FACE OF THE
APPALACHIANS BUY TUESDAY MORNING...RESULTING IN A COOL NORTHEASTERLY
WINDFLOW ACROSS THE AREA. MEANWHILE...OUR NEXT UPPER LEVEL TROUGH
WILL PASS ACROSS THE PLAINS...DRAWING ANOTHER WAVE OF WARM GULF
MOISTURE NORTHWARD ALONG THE APPALACHIAN CHAIN. RAIN ASSOCIATED WITH
THE TROUGH WILL COVER MUCH OF THE AREA DURING THE MORNING...BUT DO
NOT ANTICIPATE WIDESPREAD WINTRY PRECIPITATION ISSUES AS THE PACIFIC
HIGH PRESSURE SYSTEM HUGGING THE SURFACE WILL BE WARMER THAN THE
HIGH WHICH CONTRIBUTED TO FREEZING PRECIPITATION THIS PAST WEEKEND.
REGARDLESS...EXPECT TEMPERATURES TO REBOUND LITTLE...IF ANY...FROM
OVERNIGHT LOWS DUE TO THE RAIN...WITH AFTERNOON HIGHS RANGING FROM
AROUND FREEZING IN SOUTHEAST WEST VIRGINIA...TO THE LOW 40S ACROSS
NORTHERN NORTH CAROLINA.

THE UPPER LEVEL TROUGH WILL PASS EAST OF OUR AREA TUESDAY NIGHT...
TAKING REMAINING PRECIPITATION WITH IT FOR THE MOST PART...ALTHOUGH
A FEW UPSLOPE SNOW SHOWERS MAY LINGER ACROSS SOUTHEAST WEST VIRGINIA
INTO LATE EVENING. HIGH PRESSURE WILL BUILD IN FROM THE WEST...
BRINGING A RETURN OF SOME SUNSHINE FOR WEDNESDAY.
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&&

.LONG TERM /THURSDAY THROUGH SATURDAY/...
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AS OF 310 PM EST SATURDAY...

SURFACE HIGH PRESSURE REMAINS OVER MUCH OF THE EASTERN UNITED STATES
THURSDAY AND FRIDAY WHICH WILL KEEP TEMPERATURES NEAR OR SLIGHTLY
BELOW NORMAL.

WEAK NORTHERN STREAM SHORTWAVE COMING THROUGH EARLY THURSDAY...BUT
MODELS KEEP FORECAST AREA DRY. NEXT ORGANIZED SYSTEM COMES OUT OF
SOUTHERN STREAM FRIDAY NIGHT THROUGH SATURDAY. THIS TIMING LEANS
TOWARD SLOWER ECMWF.
-- End Changed Discussion --

&&

.AVIATION /10Z SUNDAY THROUGH THURSDAY/...
AS OF 1145 PM EST SATURDAY...

VERY POOR AVIATION CONDITIONS EXPECTED THROUGH THE TAF VALID
PERIOD. STRONG WAA ALOFT WILL RESULT IN SIGNIFICANT ISENTROPIC
LIFT OVER AN INTENSIFYING COLD AIR WEDGE AS ARCTIC HIGH PRESSURE
MOVES FROM THE GREAT LAKES REGION TOWARD NY/PA BY SUNDAY MORNING.
COLD AIR AT THE SFC WILL BE RE-ENFORCED AS PCPN FALLS FROM THE
WARMER AIR ABOVE INTO THE COLD SFC AIR MASS...WHICH SHOULD BEGIN
FROM SW-NE IN THE 08Z-10Z TIME FRAME...REACHING THE NE CORNER OF
THE CWA BY 12Z. THIS WILL SET THE STAGE FOR A PROLONGED PERIOD OF
MOSTLY -FZRA...WITH SIGNIFICANT ACCUMULATIONS OF ICE FROM 0.25 TO
0.50 INCH EXPECTED ACROSS MANY PARTS OF THE FORECAST
AREA...INCLUDING ALL TAF SITES. THE COLD AIR MAY BE DEEP ENOUGH
INITIALLY ACROSS THE NORTHERN PARTS OF THE FORECAST AREA FOR MINOR
1-3 INCH ACCUMULATIONS OF SLEET AND SNOW. MVFR CIGS AND VFR VSBYS
WILL REMAIN IN PLACE UNTIL PCPN BEGINS IN THE 08Z-10Z TIME
FRAME...THEN WILL QUICKLY LOWER TO IFR CIGS AND VSBYS WITH
POCKETS OF LIFR CIGS. LITTLE TO NO IMPROVEMENT THEN EXPECTED
THROUGH THE REMAINDER OF THE TAF VALID PERIOD. WINDS...MOSTLY
NE-E THROUGH THE TAF VALID PERIOD WITH SPEEDS 5-10KTS...WITH LOW
END GUSTS ACROSS THE PIEDMONT THROUGH 00Z MON WITH SURGING
WEDGE/ARCTIC AIR FROM THE N-NE AND SFC LOW PRESSURE DEVELOPING IN
RESPONSE TO UPSTREAM SHORT WAVE ENERGY.

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

.AVIATION EXTENDED...
WEATHER WILL BE QUITE UNSETTLED THROUGH THE FIRST PART OF THE WEEK.
A COLD FRONT PUSHES THROUGH ON MONDAY BUT GETS HUNG UP JUST TO OUR
SOUTH AS MULTIPLE WAVES OF ENERGY RIPPLE ALONG. THIS WILL KEEP MVFR
TO IFR CONDITIONS AROUND UNTIL HIGH PRESSURE BUILDS IN FOR WEDNESDAY
AND THURSDAY WITH A RETURN TO VFR. HOWEVER...KBLF/KLWB/KBCB MAY HAVE
SOME MVFR CONDITIONS TO DEAL WITH DUE TO UPSLOPE NW FLOW.

&&

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

&&

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