FXUS61 KRNK 010839
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
339 AM EST TUE DEC 1 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD JUST SOUTH OF THE AREA TODAY BEFORE
SLIDING EAST AND OFFSHORE TONIGHT. STRONG LOW PRESSURE ALONG THE
GULF COAST TONIGHT WILL LIFT NORTH ALONG THE APPALACHIANS
WEDNESDAY INTO WEDNESDAY NIGHT...REACHING NEW ENGLAND EARLY
THURSDAY. THIS SHOULD BRING ANOTHER ROUND OF SIGNIFICANT RAINFALL
FOR MID WEEK. MUCH COLDER AIR WILL FOLLOW THE TRAILING COLD FRONT
INTO THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
STILL SEEING SOME LOW CLOUDS ACROSS THE FAR WEST ATTM OTRW EXPECT
VERY DRY AIR TO WIN OUT THIS MORNING AS HIGH PRESSURE BUILDS IN FROM
THE SW AND REMAINS IN PLACE TODAY. MAY ALSO SEE SOME HIGH CLOUDS
SHEAR NE THRU THE RIDGE LATER TODAY BUT NOT ENOUGH TO DETER MAINLY
SUNNY SKIES THRU AFTERNOON UNDER SUBSIDENCE AND FAST WESTERLY
CONFLUENT FLOW ALOFT. ALSO WITH THE 85H COLD POCKET QUICKLY PULLING
OUT AND THE SURFACE HIGH RIDGING IN SHOULD SEE THE WIND GRADIENT
WEAKEN THIS MORNING ALLOWING FOR LIGHTER WINDS BY AFTERNOON. QUICK
REBOUND IN TEMPS ALOFT PLUS HEATING OF DRY AIR UNDER WESTERLY FLOW
SUGGESTS TEMPS LIKELY PUSHING THE WARM SIDE OF MOS SO NUDGED UP IN
SPOTS THIS AFTERNOON.
SURFACE RIDGE QUICKLY KICKS OFFSHORE OVERNIGHT AS LOW PRESSURE
DEVELOPS ALONG THE GULF COAST AND STARTS TO LIFT NORTH LATE.
INCREASING SE FLOW BETWEEN THE TWO SHOULD BEGIN TO INCREASE MOISTURE
PRETTY QUICK ESPCLY AFTER MIDNIGHT AHEAD OF A SLUG OF ISENTROPIC
LIFT PROGGED JUST SW OF THE CWA BY MORNING. HOWEVER THE COLUMN
REMAINS RATHER DRY IN THE LOW LEVELS EXCEPT OVER THE FAR SW WHERE
UPSLOPE LIKELY WILL CAUSE PRECIP TO OVERCOME THIS DRY POCKET SOONER.
THIS MAY PRODUCE IN SPOTTY -RA BY DAYBREAK AND IF FASTER/HEAVIER
COULD RESULT IN SOME MIX TO WET SNOW AT ELEVATION PER EVAPORATION SO
KEEPING A MENTION OTRW 20/30 POPS AT BEST. ELSW EXPECT A QUICK
INCREASE IN HIGH CLOUDS DURING THE EVENING THEN THICKENING OVERNIGHT
BUT STILL DRY. LOW TEMPS TRICKY PENDING TIMING OF THICKER CLOUD
CANOPY AND HOW FAST THINGS COOL OFF IN THE EVENING WHEN THE CIRRUS IS
RELATIVELY THIN. APPEARS COLDEST NE/VALLEYS AND WARMER AT ELEVATION
AS THE SE JET INCREASES SO RANGE FROM 40ISH RIDGES TO SOME LOWER 30S
VALLEYS OK FOR NOW.
&&
.SHORT TERM /WEDNESDAY THROUGH FRIDAY/...
CLOSED UPPER LOW OVER NRN MEXICO IS BEGINNING TO MOVE EASTWARD...AND
SHOULD ACCELERATE AND TRACK EAST-NORTHEAST IN RESPONSE TO THE
DIGGING NR STREAM TROUGH ENTERING THE NWRN U.S. THE ASSOCIATED
DEEPENING SFC LOW WILL TRACK NORTHEASTWARD OUT OF THE GULF OF MEXICO
WEDNESDAY...AND MODELS CONTINUE TO SHOW A TRACK WEST OF THE
MTNS...WITH THE LOW IN UPSTATE NY BY THU MORNING. WITH A TRACK WEST
OF THE MTNS...AND MODELS CONTINUING TO SHOW A VERY STRONG
SOUTHEASTERLY LLJ WEDNESDAY...WE HAVE OPTED TO ISSUE A HIGH WIND
WARNING FOR THE SW MTNS OF VA AND INTO MERCER COUNTY WV. THIS AREA
IS CLIMATOLOGICALLY FAVORED FOR HIGH MOUNTAIN WAVE WIND GUSTS WITH A
STRONG SOUTHEAST JET. ALL MODELS HAVE A 60+ KNOT JET AT 850 MBS
DURING THE DAY WED. STRONGEST JET IS AROUND 18Z...BUT STRONG WIND
GUSTS MAY OCCUR IN THE MORNING SINCE THIS WILL BE BEFORE RAIN STARTS
AND CEILINGS LOWER. HAVE THE TIME WINDOW FOR THE HIGH WIND WATCH 600
AM WED THRU MIDNIGHT...WITH GUSTS UP TO 60 MPH. AS FOR THE RAIN
WED...HAVE KEPT WITH THE SLOWER TIMING CLOSER TO THE NAM WITH THE
SFC LOW TRACKING SO FAR WEST. WITH NO DAMMING EVIDENT...SHOULD SEE
RAIN BREAK OUT EARLIEST IN UPSLOPE AREAS OF NW NC AND FAR SW VA.
SHOULD HAVE RAIN ACROSS THE CWA BY THE END OF THE DAY. FINALLY...
WITH MODELS STILL INDICATING A CONVECTIVE LINE DEVELOPING ALONG THE
SFC FRONT ACROSS GA AND SC...THIS MAY TEND TO CUT OFF DEEP MOISTURE
TRANSPORT INTO THE REGION. HAVE KEPT THE QPF LOWER THAN HPC GUIDANCE
FOR THIS REASON...EXCEPT FOR HEAVIER UPSLOPE RIGHT ALONG THE BLUE
RIDGE. THERE IS A SLIGHT CHC THAT THE CONVECTION MAY REACH THE
PIEDMONT AREAS LATE IN THE DAY AND IN THE EVENING...SO I HAVE
INCLUDED A SLIGHT CHC OF TSTMS OUT THAT WAY. STILL LOOKS LIKE A DRY
SLOT WILL MOVE INTO THE AREA OVERNIGHT AS THE UPPER JET SHIFTS EAST
TO OVER THE SRN APPLNS. STRONGEST COLD AIR ADVECTION SHOULD HOLD OFF
UNTIL DURING THE DAY THU...SO NOT MUCH THREAT OF SNOW IN THE MTNS
EVEN LATE WED NIGHT.
WITH MORE OF A WEST...OR EVEN WEST-SOUTHWEST FLOW BEHIND THE FRONT
LATE WED NIGHT AND THURSDAY...IT IS NOT THE BEST UPSLOPE COMPONENT.
HOWEVER...MODELS DO SHOW DEEP ENOUGH MOISTURE FOR SOME SHOWERS...SO
I HAVE KEPT THE WESTERN UPSLOPE POPS GOING. THE RAIN SHOWERS WILL BE
CHANGING TO SNOW SHOWERS IN THE HIGHER ELEVATIONS THU MORNING...AND
IF THE SHOWERS CAN KEEP GOING...WILL CHANGE OVER INTO THE LOWER
ELEVATIONS IN THE LATE AFTERNOON. SOME LIGHT SNOW ACCUMS ARE
POSSIBLE THURSDAY ABV 3K FEET. WILL BE A COLD DAY THURSDAY IN THE
MTNS WHERE TEMPS WILL STRUGGLE TO GET OUT OF THE 30S.
HIGH PRESSURE RIDGES EASTWARD FROM THE TN AND OHIO VALLEYS ACROSS
THE CENTRAL APPLNS FRIDAY...AND ALTHOUGH THE LOW LEVEL FLOW REMAINS
WEST TO NORTHWEST WITH SOME LOW LEVEL MOISTURE...IT LOOKS LIKE
UPSLOPE SHOWERS WILL BE DECREASING WITH MORE OF AN ANTI-CYCLONIC
FLOW. I HAVE LOWERED THE POPS FRIDAY...AND CONFINED THEM TO JUST THE
FAR WESTERN SLOPES. FRIDAY WILL BE CHILLY ACROSS THE CWA- BUT
ESPECIALLY IN THE MTNS.
&&
.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
THE 00Z GFS/ECMWF MIX SHOWS A WAVE ROUNDING THE TROUGH IN THE
SOUTHERN PLAINS...GRABBING SOME GULF MOISTURE...THEN PRODUCING
LIGHT SNOW IN THE WEST AND RAIN/SNOW OUT EAST LATE FRIDAY NIGHT
AND SATURDAY. HOWEVER THE DEEPER MOISTURE LOOKS TO REMAIN CLOSER
TO THE COAST WITH INLAND PRECIP MAINLY THE RESULT OF THE MID LEVEL
SUPPORT AND UPPER JET TO THE WEST OF THE OFFSHORE COASTAL LOW. JUST
HOW MUCH THE UPPER TROF CAN SHARPEN...AND HOW CLOSE TO THE COAST
THE SURFACE LOW TRACKS KEYS TO THE AMOUNT OF RETURN INLAND
MOISTURE...AND WHETHER OR NOT THE DEEP RH GETS SHEARED OUT TO THE
NE WITH THE FAST FLOW UNDER THE POSITIVE TILTED TROF. FOR NOW WILL
KEEP THINGS MAINLY DRY AND SEE IF LATER GUIDANCE BRINGS A BETTER
CONSENSUS WITH TIME.
THE COLD FRONTAL BOUNDARY FROM WEDNESDAY NIGHT RAIN
EVENT WILL BE ALONG THE SOUTHERN TIP OF FLORIDA. GIVEN THIS
PATTERN...A MID LEVEL WAVE COULD RIDE OVER THE AREA BUT MOISTURE
SHOULD ONLY CREATE OVERCAST SKIES TO POSSIBLE FLURRIES. THE GFS IS
PRODUCING A TENTH TO A QUARTER INCH OF LIQUID PRECIP...WHICH IS
WAY OVER DONE. LIKING THE ECMWF WITH SHORT WAVES ROUNDING THE
TROUGH...BUT KEEPING BULK OF PRECIPITATION OVER FLORIDA.
TEMPERATURES WILL REMAIN BELOW NORMAL THROUGH THE WEEKEND WITH THE
TROUGH REMAINING TO THE WEST FRIDAY NIGHT FOLLOWED BY A CHILLY
SURFACE HIGH OVER THE WEEKEND. TEMPERATURES ARE EXPECTED TO REBOUND
EARLY NEXT WEEK WITH A PASSING OF A WARM FRONT.
&&
.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
VFR CONDITIONS EXPECTED THROUGH THE PERIOD AS NW WINDS WILL SHIFT
MORE TO THE SOUTHWEST TUESDAY AFTERNOON...THEN SE TUE EVENING.
ANOTHER STORM SYSTEM WILL BRING A GOOD CHANCE FOR SIGNIFICANT
RAIN BY WEDNESDAY...WITH WIDESPREAD IFR CONDITIONS...POSSIBLY
CONTINUING THROUGH THURSDAY. STRONG SE WINDS ALSO EXPECTED AHEAD
OF THIS SYSTEM IN BLF BY 12Z WED.
UPSLOPE SNOW SHOWERS LOOK TO LINGER MVFR CONDITIONS ACROSS SE WVA
INTO FRIDAY WITH VFR ELSEWHERE.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...HIGH WIND WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY
EVENING FOR VAZ007-009-010-012-015.
NC...NONE.
WV...HIGH WIND WATCH FROM WEDNESDAY MORNING THROUGH WEDNESDAY
EVENING FOR WVZ042.
&&
$$
SYNOPSIS...JH/KM
NEAR TERM...JH
SHORT TERM...JJ
LONG TERM...JH/RCS
AVIATION...AMS/WP
