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413
FXUS61 KRNK 190927
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
427 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 218 AM EST FRIDAY...

CLOUDS AGAIN THE MAIN CONCERN TODAY AS SHORTWAVE EXITS EARLY THIS
MORNING AND WEAK SUBSIDENCE FILLS IN BEFORE THE NEXT WAVE APPROACHES
FROM THE SW LATE TONIGHT. IR PICS SHOW A VARIETY OF MID DECK AS WELL AS
HIGH END STRATO-CU PASSING ACROSS WITH LINGERING LOW CLOUDS PINNED
ALONG THE NW SLOPES. GUIDANCE HANGS ON TO THIS SCENARIO INTO MID
MORNING BEFORE SHOWING PERHAPS ENOUGH DRYING ALOFT TO AID CLEARING BY
EARLY AFTERNOON AS BRIEF SHORTWAVE RIDGING BUILDS EAST. THIS SUPPORTS
GOING WITH MORE SUN BY THIS AFTERNOON BEFORE HIGH/MID CLOUDS
MAKE A RETURN OVER THE SW LATE. 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 WOULDNT 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 /09Z FRIDAY THROUGH TUESDAY/...
AS OF 1045 PM EST THURSDAY...

NOT MUCH CHANGE TO THE AVIATION FORECAST...THOUGH CONFIDENCE IS
LESS THAT BLF WILL DROP BELOW 1KFT PER UPSTREAM OBS. STILL WILL
HAVE A TEMPO GROUP TOWARD 12Z FOR BLF DROPPING TO 9H FEET FOR A
COUPLE HOURS.

OTHERWISE BECOMING MVFR AT BLF/LWB OVERNIGHT THEN BACK TO VFR BY
MIDDAY FRIDAY...WHILE REST OF THE TAF SITES STAY VFR. COULD SEE
SOME SCT SUB 3KFT CLOUDS ACROSS BCB BUT CONFIDENCE HIGH THAT
THREAT OF BKN IS NOT GOING TO HAPPEN.

CLOUDS AHEAD OF THE NEXT SYSTEM WILL BE INCREASING OVERNIGHT
FRIDAY SO EXPECT MAINLY CIRROSTRATUS IN THE LATE EVENING ACROSS
THE REGION.

EXTENDED DISCUSSION...

THE SAT SYSTEM NOW HAS TRENDED WEAKER AND WILL SHIFT MOST OF THE
PRECIP ACROSS THE CAROLINAS...THOUGH STILL WILL SEE SOME WINTRY
MIX BUMP UP INTO THE SE WV/SW VA CORRIDOR INTO THE NC
MTNS...THOUGH TRENDS ARE SHOWING LESS. EXPECT SUB VFR THOUGH AT
TIMES SATURDAY INTO SAT NIGHT.

ON THE HEELS OF THIS  SYSTEM WILL BE ANOTHER SYSTEM TO
POTENTIALLY IMPACT MAINLY THE EASTERN PORTION OF THE REGION SUNDAY
NIGHT INTO MONDAY...WITH YET ANOTHER SYSTEM SLATED FOR LATE
TUESDAY INTO WEDNESDAY. THESE SYSTEMS ARE EXPECTED TO BRING A
PERIOD MAINLY RAIN BUT COULD BE SOME WINTRY WX AS WELL ESPECIALLY
IN THE MOUNTAINS. EXPECT POTENTIAL LOW LEVEL WIND SHEAR AS WELL
AND POOR FLYING WEATHER MONDAY.

&&

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

&&

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




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