FXUS61 KRNK 021441
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
941 AM EST WED DEC 2 2009

.SYNOPSIS...
LOW PRESSURE ALONG THE GULF COAST WILL TRACK WEST OF THE
APPALACHIANS BY THIS EVENING AND INTO THE NORTHEAST STATES BY
EARLY THURSDAY. WEAK HIGH PRESSURE FOLLOWING THIS SYSTEM SHOULD
BUILD INTO THE REGION THURSDAY INTO THURSDAY NIGHT. ANOTHER
AREA OF LOW PRESSURE MAY DEVELOP ALONG THE SOUTHEAST COAST AND
MOVE OFFSHORE THIS WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
SOLID SHIELD OF RAIN HAS MOVED INTO THE NRN CWA...WITH ONE REPORT
OF SLEET MIXED IN ACROSS THE VA HIGHLANDS EARLIER. MODEL SOUNDINGS
SUGGEST POTENTIAL FOR SLEET FOR THE NEXT COUPLE OF HOURS...BUT
WILL SEE WARM AIR TAKE OVER BY MIDDAY WITH ALL RAIN. STILL KEEPING
WITH CATEGORICAL POPS MOST PLACES WITH LIKELY ON THE WRN/ERN EDGES
OF THE CWA. REGIONAL RADAR SHOWING LIGHTER PRECIP EXPECTED INTO
EARLY AFTERNOON B4 SOUTHEAST ENHANCMENT GETS GOING. NEW 12Z NAM
SHOWING HEAVIER PRECIP OVER GA THIS MORNING SPREADING INTO THE SRN
CWA BY 21Z. 

12Z SOUNDINGS SHOWING 8H WINDS MORE OUT OF THE SOUTH THAN
SOUTHEAST...BUT ALREADY GETTING MORE OF A SOUTHEAST TURN BASED ON
OBS. SPEEDS INCREASE TO 50 KNOTS+ AT 18Z...SO ONGOING
WARNING/ADVISORY LOOKS OK...BUT WITH WEDGE IN PLACE OVER THE BLUE
RIDGE/FOOTHILLS/NEW RIVER VALLEY...MAY BE HARD PRESSED TO GET
ADVISORY WINDS EXCEPT THE PEAKS. SE COMPONENT ALOFT QUICKLY VEERS
SOUTH AND THEN SW THIS EVENING SO EXPECT MAY BE ABLE TO CANCEL
EARLY LATER TODAY.

GUIDANCE HAS COME AROUND TO A BIT FASTER SOLUTION IN
ADVANCING THE SURFACE LOW WEST OF THE MOUNTAINS THIS AFTERNOON
WITH THE AXIS OF HEAVIER RAIN TAKING SHAPE A LITTLE FARTHER TO THE
SE. WILL SEE A PERIOD OF STRONG SE UPSLOPE SOUTHERN BLUE RIDGE
THIS AFTERNOON BUT SHORT LIVED WITH THE 9H LEVEL FLOW QUICKLY
VEERING SOUTHERLY BY EVENING. ALSO SOME POTENTIAL FOR HEAVIER
PRECIP TO HEAD MORE TO THE SE TODAY WHERE SOME INSTAB EXISTS WHILE
DRY SLOT TAKES AIM UP ALONG THE APPALACHIANS. THEREFORE WENT A
LITTLE LOWER ON QPF BUT STILL 1-2 INCHES ESPCLY ALONG/EAST OF THE
BLUE RIDGE INTO THIS EVENING. GIVEN EXPECTED LOWER RATE TYPE
STRATIFORM RAINFALL TODAY APPEARS AREA STREAMS/CREEKS CAN HANDLE
WITHOUT NEED FOR A FLOOD WATCH AT THIS POINT. OTRW LITTLE CHANGE
IN POPS WITH MOST AREAS BUMPING UP TO CATEGORICAL BY AFTERNOON.
HIGH TEMPS VERY TRICKY GIVEN ONSET OF WEDGE ESPCLY CENTRAL/EAST
AND WARMING ON THE RIDGES. WENT CLOSER TO THE COLDER MET PER
EVAPORATIVE POTENTIAL EARLY ON AND LITTLE RISE OUTSIDE THE FAR
WESTERN/NE ZONES AFTER MID MORNING.

SCENARIO TRANSFORMS FROM MORE ISENTROPIC TO DYNAMICAL THIS EVENING 
AND EARLY TONIGHT AS THE UPPER AIR SUPPORT TRAILING THE SURFACE LOW 
CATCHES UP FROM THE SW. DIFFLUENCE AND STRONG FORCING TO THE EAST
OF THE VORT COMPLEX PASSING JUST WEST MAY ACT TO DEVELOP A BAND OF
EMBEDDED CONVECTION WITH THIS MORE ELEVATED IN THE WEDGE BUT
POSSIBLY SURFACED BASED SE IF THE WARM SECTOR PULLS A LITTLE
FARTHER TO THE WEST. LATEST NAM SUPPORTS ELEVATED TSRA WELL INTO
THE COOL POOL SO INCHED TSRA MENTION TO JUST SE OF THE BLUE RIDGE
THIS EVENING. DRY SLOT ALOFT AND ARRIVAL OF THE SURFACE COLD FRONT
FROM THE WEST SHOULD TAPER SHRA AFTER MIDNIGHT WITH ONLY SOME WRAP
AROUND -SHRA LINGERING WESTERN SLOPES BY MORNING. THUS HIGH POPS
LOWERING TO LOWER CHANCE MOST AREAS LATE WITH LIKELY LITTLE
LEFTOVER PRECIP SOUTH PER INCREASING DOWNSLOPE. EXPECT LOW TEMPS
OUT EAST TO OCCUR DURING THE EVENING AND THEN RISE...WITH SOME
FALLS WEST LATE AS THE FRONT PUSHES THRU BUT ONLY WEAK COLD ADVECTION
AT THIS POINT WHICH KEEP MOST SPOTS UPPER 30S TO LOWER 40S.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/...
THURSDAY INTO FRIDAY LOOK FOR A DECREASING PRESSURE GRADIENT AS THE 
CENTER OF HIGH PRESSURE APPROACHES THE REGION. THIS WILL HELP WINDS 
TREND SLOWER...BUT THEY WILL CONTINUE MAINLY FROM THE 
WEST-NORTHWEST. THIS WILL HELP MAINTAIN UPSLOPE RAIN/SNOW SHOWERS IN 
THE PREFERRED HIGHER ELEVATIONS OF SOUTHEAST WV AND NEIGHBORING 
PARTS OF SW VIRGINIA...SOUTH INTO THE NORTHERN MOUNTAINS OF NC. 
HOWEVER...COVERAGE DURING THIS PERIOD WILL BE ON THE DECREASE. 

WE WILL HAVE A BRIEF BREAK IN THE WEATHER BY LATE FRIDAY AFTERNOON 
INTO EARLY FRIDAY EVENING. BY LATE FRIDAY NIGHT INTO EARLY 
SATURDAY...OUR EYES TURN TO THE EAST AS AN AREA OF LOW PRESSURE IS 
PROGGED TO HEAD NORTH ALONG THE EAST COAST. AS IT DOES...GUIDANCE IS 
STILL IN REASONABLE AGREEMENT OF A WESTERN FLANK DEFORMATION ZONE 
SETTING UP OVER THE FORECAST AREA IN ASSOCIATION WITH THIS PASSING 
LOW. HAVE CONTINUED WITH CHANCE POPS DURING SATURDAY WITH 
PRECIPITATION ENDING SATURDAY NIGHT.

FOR TEMPERATURES DURING THE THURSDAY TO SATURDAY NIGHT PERIOD...HAVE 
MADE ONLY MINOR TWEAKS TO THE PREVIOUS FORECAST...AND MOST OF THE 
TWEAKS WERE TOWARD THE SLIGHTLY COOLER SIDE.

&&

.LONG TERM /SUNDAY THROUGH TUESDAY/...
AN UPPER LEVEL TROUGH WILL MOVE QUICKLY FROM THE MID WEST SATURDAY 
MORNING TO THE EAST COAST SATURDAY NIGHT. A STRONG SHORT WAVE AT THE 
BASE OF THIS TROUGH WILL TRACK FROM TEXAS SATURDAY MORNING TO OFF 
THE VA/NC COAST SATURDAY EVENING. THIS DISTURBANCE WILL PICK UP SOME 
MOISTURE DURING ITS TRAVEL AND BRING A CHANCE FOR PRECIPITATION TO 
THE AREA ON SATURDAY. YESTERDAY...THE 12Z GFS WAS THE ONLY MODEL 
SHOWING THIS DISTURBANCE WITH PRECIPITATION OVER THE AREA. 
TODAY...THE 12Z GFS IS STILL SHOWING IT AND NOW THE ECMWF HAS IT AS 
WELL. THE 12Z GEM MAINTAINING ITS CONTINUITY AND LOOKS SIMILAR TO 
YESTERDAY ECMWF...KEEPING ANY PRECIPITATION OVER FLORIDA. MODELS 
CONTINUE TO SHOW WEST TO NORTHWEST LOW LEVEL FLOW OVER THE REGION 
AND AHEAD OF THE FRONT FRIDAY NIGHT/SATURDAY MORNING. WITH THE SPEED 
OF THIS SYSTEM COMING IN TO A RELATIVELY DRY AIR MASS...STILL THINK MODELS 
ARE OVER DOING LIQUID PRECIPITATION OVER THE AREA. IN LIGHT OF 
ANOTHER MODEL MOVING THIS DISTURBANCE OVER THE REGION...WILL ADD LOW 
CHANCE POPS ON SATURDAY...BUT CONFIDENCE IS VERY LOW.

FOR SAKE OF AGREEMENT...LETS SAY THIS SYSTEM DOES MOVE IN WITH 
PRECIPITATION. GFS FORECAST SOUNDINGS SHOWING A SHALLOW WARM SURFACE 
BOUNDARY LAYER...LESS THAN A 1000 FT ALONG THE FOOTHILLS AND FROZEN 
SOUNDING ACROSS THE MOUNTAINS. IF PRECIPITATION DOES FALL SATURDAY 
MORNING...IT WILL MOSTLY LIKELY BE SNOW. INTO THE 
PIEDMONT...BOUNDARY LAYER A LITTLE THICKER AND AROUND 1400-1800 FEET 
FOR P-TYPE TO BE RAIN...POSSIBLY MIXED WITH SNOW EARLY. OF COURSE 
THIS DEPENDS ON THE GFS VERIFYING...WHICH HAS A HISTORY OF A COLD 
BIAS DURING THE COOL SEASON...ESPECIALLY IN THE LONG RANGE.  

ONCE THE UPPER LEVEL TROUGH TRACKS OFF THE EAST COAST...HIGH 
PRESSURE WILL BUILD IN WITH ZONAL FLOW ALOFT. THE REGION SHOULD 
REMAIN PRECIPITATION FREE THROUGH EARLY NEXT WEEK. TEMPERATURES 
THROUGH THE PERIOD WILL STAY BELOW NORMAL BUT MODERATE EACH DAY.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
CIGS WILL CONTINUE TO LOWER FROM SW TO NE THIS MORNING WITH RAIN
SPREADING ACROSS MOST OF THE TAF SITES BY MID MORNING AND
CONTINUING THRU THE DAY. ALSO...A STRONG SOUTHEAST LOW LEVEL JET
WILL BRING LOW LEVEL WIND SHEAR TO ALL TAF SITES TODAY...WITH
WINDS MIXING DOWN TO THE SURFACE AT KBLF WHERE GUSTS TO 35 KNOTS
OR BETTER POSSIBLE ESPCLY THIS AFTERNOON. OTRW THE MAIN ISSUES
WITH THE TAFS WILL BE THE LOW CLOUD THREAT AND REDUCTIONS IN VSBYS
AS THE RAIN INCREASES. IF THE RAIN COMES DOWN HARD ENOUGH...WE
USUALLY KEEP CIGS ABOVE IFR...BUT IF THE RAINS ARE VERY LIGHT THEN
EXPECT IFR OR LOWER TO IMPACT THE SITES. AT THIS POINT LEANING
TOWARD MVFR CIGS WITH A PERIOD OF IFR VSBYS IN RAIN ESPECIALLY
FROM ROANOKE EAST TO LYH/DAN. POOR FLYING CONDITIONS SHOULD
CONTINUE INTO THE EVENING BEFORE A COLD FRONT SWEEPS THRU AFTER
MIDNIGHT ALLOWING CIGS TO LIFT INTO MVFR IF NOT BETTER ACROSS THE
EAST...WITH ONLY SCATTERED -SHRA REMAINING PRIOR TO 12Z THURSDAY.

THIS LOW PRESSURE STORM SYSTEM LIFTS NORTHEAST BY THURSDAY MORNING WITH
IMPROVING CONDITIONS EAST OF THE MOUNTAINS ON THURSDAY. EXPECT
UPSLOPE SNOW SHOWERS TO LINGER MVFR CONDITIONS ACROSS SE WVA INTO
FRIDAY WITH VFR ELSEWHERE. ANOTHER STORM SYSTEM COULD BRING LOWER
CIGS AND POSSIBLY A LITTLE MORE WINTRY PRECIP FOR SATURDAY
FOLLOWED BY VFR UNDER HIGH PRESSURE FOR THE END OF THE WEEKEND.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR VAZ011-013-014-
     016>020-022>024-032>035.
     HIGH WIND WARNING UNTIL MIDNIGHT EST TONIGHT FOR VAZ007-009-
     010-012-015.
NC...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR NCZ001>003-018-
     019.
WV...WIND ADVISORY UNTIL MIDNIGHT EST TONIGHT FOR WVZ043>045.
     HIGH WIND WARNING UNTIL MIDNIGHT EST TONIGHT FOR WVZ042.

&&

$$
SYNOPSIS...JH/KM
NEAR TERM...JH/WP
SHORT TERM...DS
LONG TERM...RCS
AVIATION...DS/JH