Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 191432
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
932 AM EST FRI DEC 19 2014

.SYNOPSIS...
HIGH PRESSURE OVER THE UPPER MIDWEST WILL GRADUALLY BUILD SOUTHEAST
ACROSS THE AREA RESULTING IN OVERALL DRY WEATHER INTO TONIGHT. A
WEAK AREA OF LOW PRESSURE WILL DEVELOP ALONG THE GULF COAST
STATES LATE TONIGHT AND MOVE EAST OVER THE SOUTHEAST STATES ON
SATURDAY. THIS SYSTEM WILL BRING A PERIOD OF LIGHT WINTRY
PRECIPITATION TO MAINLY SOUTHERN AND WESTERN AREAS SATURDAY
MORNING BEFORE TAPERING OFF SATURDAY AFTERNOON.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 928 AM EST FRIDAY...

VERY LITTLE TO CHANGE IN THE FORECAST. LOWER CLOUDS STICKING
AROUND TIL ABOUT NOON IN THE WRN SLOPES...WITH MOST AREAS STAYING
SUNNY. WILL SEE SOME THIN HIGH CLOUDS ARRIVING FROM THE SOUTHWEST
THROUGH THE AFTERNOON...BECOMING MORE OPAQUE AS WE HEAD TOWARD
DUSK.

PREVIOUS VALID DISCUSSION...

HIGH TEMPS REMAIN A BIT TRICKY GIVEN THE WIDE RANGE OF VALUES TO
INIT THIS MORNING AND TIMING OF CLOUD EXODUS THIS AFTERNOON.
OVERALL MOS A BIT COOLER THAN PREVIOUS SO LOWERED A DEGREE OR TWO
IN SPOTS BUT NOT AS COOL AS THE MET TODAY PER MORE EXPECTED
INSOLATION.

MID LEVEL WAVE CURRENTLY HEADING NE OUT OF NEW MEXICO WILL GIVE RISE TO
WEAK SURFACE LOW PRESSURE ALONG THE NORTHERN GULF LATE TONIGHT WITH
PLENTY OF SHEARED MOISTURE ZIPPING NE INTO THE REGION OVERNIGHT.
HOWEVER THE SYSTEM STILL LOOKS TO REMAIN WEAK GIVEN THE MAIN UPPER JET
WELL TO THE SOUTH AND DAMPENING OF THE MID LEVEL SHORTWAVE AS IT GETS
BOOTED EAST WITHOUT PHASING VIA A SEPARATE NORTHERN STREAM VORT. BEST
MOISTURE TRANSPORT WITH THE WEAK SURFACE LOW WILL STAY SOUTH WITH
PERHAPS A SECOND ZONE OF LIGHT PRECIP FARTHER NORTH DRIVEN BY THE COMBO
OF THE WAVE ALOFT AND WEAK ISENTROPIC LIFT INTO SW SECTIONS LATE.
MODELS CONTINUE TO ONLY SHOW VERY LIGHT QPF AND WOULDN`T TAKE
MUCH LIFT TO THE SOUTH TO TOTALLY CUT OFF MOISTURE INTO THE CWA
PER LATEST EURO. HOWEVER WITH SOME SPOTTY QPF OF UP TO A TENTH OF
AN INCH OFF THE NAM OVER THE NW NC MOUNTAINS...BROUGHT IN LOW
LIKELYS THERE BY DAYBREAK WHILE SPREADING LOW CHANCES FARTHER
NORTH ACROSS MOST OF THE MOUNTAINS/FOOTHILLS UNDER THE WAVE AXIS.
FORECAST SOUNDINGS SHOW MOST OF THE REGION BELOW FREEZING ALOFT SO
PTYPE MAINLY SNOW WITH PERHAPS THE WARMER BOUNDARY LAYER IN SPOTS
CAUSING A BIT MORE RAIN TO INIT FOOTHILLS EAST. SOME SLEET ALSO
POSSIBLE DURING THE CHANGE TO SNOW AT THE ONSET IN THESE SPOTS AS
WELL SO INCLUDED MENTION.

OVERALL SNOWFALL LOOKS TO BE LESS THAN A HALF INCH AT BEST BY
MORNING...THUS NO HEADLINES GIVEN LIGHT AMOUNTS AND POTENTIAL FOR JUST
MORE CLOUDS THAN SIGNIFICANT QPF AT THIS POINT. OTRW BECOMING CLOUDY
ALL SECTIONS WITH LOWS IN THE 20S TO LOW 30S...MAINLY THIS
EVENING...THEN STEADYING OR RISING LATE AS CLOUDS THICKEN.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
AS OF 330 AM EST FRIDAY...

WEATHER FORECAST MODELS OVER THE PAST FEW RUNS ARE SETTLING ON A
MODEST UPPER LEVEL TROUGH PASSING ACROSS THE AREA ON SATURDAY...WITH
A WEAK LOW PRESSURE SYSTEM MOVING NORTHEAST ALONG THE ATLANTIC
COAST. THIS WILL BRING LIGHT SNOW ACROSS THE AREA DURING THE MORNING
AND AFTERNOON...WITH SPOTTY ACCUMULATIONS...MOSTLY LESS THAN AN
INCH...CONFINED TO THE HIGHER RIDGES...PARTICULARLY ALONG THE BLUE
RIDGE PARKWAY SOUTH OF ROANOKE INTO THE MOUNTAIN EMPIRE. ENERGY
ASSOCIATED WITH THE UPPER TROUGH WILL EXIT TO THE EAST DURING THE
AFTERNOON...LEAVING ONLY LIGHT SNOW SHOWERS ALONG THE WESTERN RIDGES
DURING THE EVENING. OTHERWISE...WILL BE LOOKING AT DRY WEATHER
THROUGH SATURDAY NIGHT...AS ANOTHER ROUND OF HIGH PRESSURE PASSES
ACROSS EASTERN CANADA...AND BUILDS SOUTHWARD ACROSS NEW ENGLAND AND
THE MID ATLANTIC TO WEDGE AGAINST THE EASTERN FACE OF THE
APPALACHIANS.

YET ANOTHER TROUGH WILL APPROACH FROM THE WEST ON SUNDAY...
SUPPORTING DEVELOPMENT OF LOW PRESSURE ALONG THE CENTRAL GULF COAST.
SOUTHERLY FLOW OFF THE SURFACE WILL PUSH WARM GULF AIR ALONG THE
CENTRAL APPALACHIANS TO OVERRUN THE COLD NORTHEASTERLY WIND FLOW
ASSOCIATED WITH THE HIGH PRESSURE WEDGE. AS SUCH...EXPECT TO SEE A
WINTRY MIX DEVELOP SUNDAY NIGHT AS PRECIPITATION ENTERS OUR AREA.
FORECAST MODEL SOUNDINGS INDICATE THAT THE COLD AIR ASSOCIATED WITH
THE WEDGE IS DEEP ENOUGH TO CAUSE MUCH OF THE PRECIPITATION ACROSS
THE MOUNTAINS TO FALL AS A MIXTURE OF SLEET AND RAIN NORTH OF
HIGHWAY 460...WITH TEMPERATURES TOWARD THE INTERSTATE 64 CORRIDOR
BECOMING COLD ENOUGH THAT SNOW WILL BECOME MORE OF A POSSIBILITY.
STILL A LITTLE EARLY TO DISCUSS ACCUMULATIONS...BUT AS OF THIS
MORNING...IT IS LOOKING MORE LIKE AN ADVISORY CRITERIA EVENT RATHER
THAN A WARNING EVENT...ALTHOUGH THIS CAN EASILY CHANGE OVER THE NEXT
DAY OR TWO.

TEMPERATURES WILL WARM ENOUGH BY EARLY MONDAY AFTERNOON TO ALLOW
PRECIPITATION TO CHANGE MAINLY TO RAIN...POSSIBLY WITH A FEW POCKETS
OF SLEET OR FREEZING RAIN REMAINING THROUGH THE DAY. THE MAIN ENERGY
ASSOCIATED WITH THE SYSTEM WILL PASS EAST DURING MONDAY
EVENING...LEAVING ONLY PATCHES OF LIGHT PRECIPITATION TO PASS ACROSS
THE AREA OVERNIGHT.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
AS OF 230 PM EST THURSDAY...

A DEEP LONGITUDINAL TROUGH DEVELOPS SOUTH TO THE GULF OF MEXICO ON
TUESDAY WITH INCREASING SOUTHERLY LOW LEVEL FLOW ACROSS OUR
REGION...ACCOMPANIED BY INCREASING MOISTURE ADVECTION. TEMPERATURES
WILL TREND MILDER FOR HIGHS TUESDAY FROM THE MID 40S TO THE LOWER
50S.

BY TUESDAY NIGHT INTO WEDNESDAY...BOTH GFS AND ECWMF DEEPEN THE
UPPER LOW AND ASSOCIATED TROUGH AND NEGATIVELY TILT THE FEATURE SO
THAT THE TROUGH AXIS SHIFTS TO OFF THE NORTH CAROLINA COAST...
COINCIDENT TO THE POSITION OF THE ASSOCIATED SURFACE OCCLUDED
FRONT...WITH THE TRIPLE POINT PASSING SOMEWHERE NEAR OR JUST SOUTH
OF OUR REGION. AT THIS TIME...SPC DOES NOT HAVE ANY THUNDERSTORMS IN
ITS DAY 4-8 CONVECTIVE OUTLOOK. IT LOOKS LIKE...THERE IS THE
POTENTIAL FOR OUR REGION TO HAVE ACTIVE WEATHER LATE TUESDAY NIGHT
INTO WEDNESDAY WITH PLENTY OF SHOWERS...PERHAPS VERY GUSTY WINDS AND
A FEW THUNDERSTORMS.

COLD AIR PUSHES INTO THE REGION TUESDAY NIGHT INTO WEDNESDAY
MORNING...ALLOWING FOR SOME RAIN AND SNOW SHOWERS. IF ENOUGH COLD
AIR ARRIVES QUICKLY...THERE COULD BE SOME ACCUMULATING SNOW IN THE
WESTERN MOUNTAINS. KEPT THE HIGHEST POPS OF RAIN AND SNOW SHOWERS IN
THE WEST AS THE LOW CENTER MARCHES NORTHEAST PUSHES A COLD FRONT TO
THE COAST. IN THE WAKE OF THE COLD FRONT A COOLING TRENDS WILL
CONTINUE WEDNESDAY INTO THURSDAY...WITH WEST TO NORTHWEST FLOW
ALOFT. UPPER FLOW SHIFTS TO THE SOUTHWEST AS TROF CURVES OUT IN THE
CENTRAL US WITH SFC INFLECTION OF LOW PRESSURE DEVELOPS OVER THE
TENNESSEE VALLEY BY FRIDAY MORNING.

&&

.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
AS OF 605 AM EST FRIDAY...

FLYING CONDITIONS SLOWLY IMPROVING THIS MORNING BUT STILL LOOKING
AT MVFR/OCNL IFR CIGS AT KBLF WITH LOW CLOUDS BANKED UP ALONG THE
WESTERN SLOPES...AND PERHAPS A PERIOD OF MVFR AT KLWB. LATEST
BUFKIT SOUNDINGS SUGGEST THAT MOST RESIDUAL UPSTREAM LOW CLOUDS
SHOULD MIX OUT LATER THIS MORNING WITH ALL WESTERN LOCATIONS
BECOMING VFR AROUND MID MORNING. SOME LOW END VFR SCT-BKN CLOUDS
POSSIBLE OUT EAST THIS MORNING AS WELL BUT SHOULD ONLY LAST A FEW
MORE HOURS AT BEST. OTRW SHOULD SEE WIDESPREAD VFR THIS AFTERNOON/
EVENING UNDER REDUCED CLOUDINESS BEFORE MID/HIGH LEVEL MOISTURE
STARTS TO RETURN FROM THE SW...AND LOW CLOUDS POSSIBLY SNEAK BACK
INTO KBLF/KLWB LATE WHERE INCLUDED SOME MVFR CIGS LATE.

LIGHT PRECIP WITH WEAK LOW PRESSURE TO THE SOUTH SHOULD APPROACH
THE REGION VERY LATE TONIGHT WHILE LATEST FORECAST SOUNDINGS
SUGGEST ENOUGH LOW LEVEL DRY AIR TO PRECLUDE MUCH FROM REACHING
THE SURFACE. THEREFORE MAINTAINING VFR UNDER LOWERING CIGS ELSW
OUTSIDE OF THE SE WEST VA SITES BUT WITHOUT ANY PRECIP MENTION AT
THIS POINT.

EXTENDED DISCUSSION...

WEAK SYSTEM WILL PASS TO THE SOUTH AND EAST SATURDAY PERHAPS
BRINGING A PERIOD OF SNOW OR WINTRY MIX ACROSS SOUTHERN/SW
SECTIONS INTO EARLY AFTERNOON BEFORE TAPERING. HOWEVER WITH THE
MAJORITY OF THE PRECIP LOOKING TO PASS SOUTH ONLY LOOKING AT BRIEF
VSBY REDUCTIONS AT WORSE...MAINLY ALONG THE KBLF-KBCB-KDAN
CORRIDOR...WHERE A PERIOD OF MVFR CIGS LOOKS LIKELY INTO SATURDAY
AFTERNOON.

ONCE THIS FEATURE EXITS BY LATE SATURDAY...WILL SEE THE NEXT WAVE
ALONG THE COAST BRING ANOTHER ROUND OF SUB-VFR CONDITIONS FOR
LATER SUNDAY NIGHT INTO MONDAY. THIS SYSTEM LOOKS TO IMPACT
AREAS ALONG AND EAST OF THE BLUE RIDGE...WITH YET ANOTHER SYSTEM
SLATED FOR LATE TUESDAY INTO WEDNESDAY AHEAD OF A STRONG COLD
FRONT. THESE SYSTEMS ARE EXPECTED TO BRING A PERIOD MAINLY RAIN
BUT COULD BE SOME WINTRY WX AS WELL ESPECIALLY IN THE MOUNTAINS
WITH THE SUNDAY NIGHT/MONDAY EVENT. EXPECT POTENTIAL LOW LEVEL
WIND SHEAR AS WELL AND POOR FLYING WEATHER FOR EARLY NEXT WEEK.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.

&&

$$
SYNOPSIS...JH/RCS
NEAR TERM...JH/WP
SHORT TERM...NF
LONG TERM...KK
AVIATION...JH/RCS/WP



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