FXUS61 KRNK 021105
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
605 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/...
PRECIP SHIELD CONTINUES TO ADVANCE QUICKLY NE TOWARD THE CWA THIS 
MORNING AHEAD OF THE DEVELOPING SURFACE LOW OVER SOUTHERN ALABAMA 
ATTM. EXPECT LOW LEVEL DRY AIR TO INITIALLY INHIBIT MUCH PROGESS TO 
THE EAST OF THE BLUE RIDGE EARLY THIS MORNING BEFORE THINGS QUICKLY 
SATURATE AS THE FLOW TURNS MORE SE ALOFT BY MIDDAY. THIS SHOULD 
LIMIT HIGHER POPS TO THE FAR SW AROUND 12Z...THEN EXPANDING ACROSS 
MOST OF THE REGION BY LATE MORNING IN RESPONSE TO THE AXIS OF 
ISENTROPIC LIFT SHIFTING UP FROM THE SOUTH. STILL SOME POTENTIAL FOR 
ENOUGH EVAPORATIVE COOLING TO SEE SOME WET SNOW AT ELEVATION MAINLY 
NW IF THE PRECIP REACHES THE SURFACE FASTER...OTRW ALL RAIN PER 
WARMING ALOFT THRU THE DAY OVERTOP INSITU CAD. 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.

WILL KEEP THE GOING NPW/WIND PRODUCTS IN PLACE TODAY ALTHO QUESTIONS 
WITH JUST HOW MUCH WILL REACH THE SURFACE OUTSIDE OF TAZEWELL/MERCER 
CTYS GIVEN THE DEVELOPING CAD. FCST RAOBS SUGGEST A CLOSE CALL ON 
WHETHER OR NOT THE 50-60 KTS ALOFT LOWER DOWN TO THE RIDGETOPS ELSW 
SO BEST TO KEEP IN PLACE WITH BEST SPEEDS FROM LATE MORNING THRU 
LATE AFTERNOON. SE COMPONENT ALOFT QUICKLY VEERS SOUTH AND THEN SW 
THIS EVENING SO EXPECT MAY BE ABLE TO CANCEL EARLY LATER TODAY. 

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 /12Z 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
SHORT TERM...DS
LONG TERM...RCS
AVIATION...AMS/DS/JH/WP