FXUS61 KRNK 112013
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
313 PM EST FRI DEC 11 2009

.SYNOPSIS...
A LARGE HIGH PRESSURE SYSTEM WILL MOVE EAST ACROSS THE THROUGH TONIGHT...THEN
OFF THE COAST SATURDAY. LOW PRESSURE WILL TRACK SOUTH OF THE
REGION OVER THE WEEKEND AND WILL LIKELY SPREAD WINTRY
PRECIPITATION INTO OUR AREA SATURDAY NIGHT INTO EARLY SUNDAY.

&&

.NEAR TERM /THROUGH SATURDAY/...
A STRONG SURFACE HIGH WILL BE OVERHEAD TONIGHT WITH ZONAL FLOW 
ALOFT. 85H RIDGE WILL ALSO BE OVER THE AREA WHICH WILL LEAD TO GOOD 
RADIATIONAL COOLING. DECOUPLING EXPECTED EARLY IN THE MOUNTAIN 
VALLEYS AND LATER IN THE EAST. WITH DEW POINTS BEING VERY DRY 
OVERNIGHT...TEMPERATURES WILL BOTTOM OUT IN THE 10-15F RANGE ACROSS 
THE WEST AND IN THE 15-20F RANGE IN THE EAST. MAV/GFS WAS THE 
COLDEST GUIDANCE WITH MET/NAM 5-10F WARMER. LIKING THE MAV/GFS 
NUMBERS FOR OVERNIGHT LOWS BUT NOT CONFIDENT TO RULE OUT MET/NAM. 
THEREFORE...TOOK A BLEND OF THE TWO WITH A SLIGHT WEIGHT TO MAV/GFS.

THE SURFACE HIGH WILL CONTINUE TO ADVANCE TO THE EAST AND OFF THE 
VA/NC COAST SATURDAY AFTERNOON. LIGHT SOUTHERLY FLOW WILL BE 
ESTABLISHED ACROSS THE WEST WHILE THE EAST REMAINS SOMEWHAT COOL. 
CLOUDS SHOULD HOLD OFF UNTIL THE LATE AFTERNOON AND WILL LIKELY SEE 
UNIFORM TEMPERATURES IN THE 40S...SOME 30S IN HIGHER ELEVATIONS AND 
SHELTERED VALLEYS. I WENT WITH THE COOLER NAM FOR HIGH TEMPERATURES.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
LOOKING AT A WINTRY EVENT SAT NIGHT INTO EARLY SUNDAY. MODELS ARE
PUSHING PRECIP INTO THE AREA AROUND THE 00Z-03Z TIME
FRAME...ALTHOUGH FAVORING SLIGHTLY SLOWER THAN THE GFS/NAM.
LEANING TOWARD THE 12Z NAM ON TEMP PROFILE WITH SOME ADJUSTMENTS
COLDER. THINKING THAT THE COLUMN AND SFC TEMPS ARE GOING TO BE
COLDER GIVEN THE PAST TWO DAYS OF TEMPS IN THE TEENS IN THE MTNS. 

THIS WILL SET THE STAGE FOR ACCUMULATING WINTRY PRECIP...ALBEIT ON
THE LIGHT SIDE AS OPPOSED TO THE PREVIOUS SYSTEM. STILL EXPECT
SLEET/SNOW MIX AT THE ONSET SAT EVENING OVER THE NC MTNS/SW VA
MTNS TO MOVE NORTH ACROSS THE AREA THROUGH MIDNIGHT. WARM NOSE
WILL CHANGE PRECIP OVER TO RAIN...AND THINK WITH SUB-FREEZING SFC
TEMPS LOOKING AT LIGHT ICE ACCRETION ACROSS THE ENITRE BLUE RIDGE
AND EITHER SIDE...WITH ANOTHER POCKET FURTHER WEST OVER THE
ALLEGHANY MTNS INTO THE GREENBRIER VALLEY. EVEN AREAS ALONG AND
NORTH OF THE ROANOKE RIVER IN THE PIEDMONT WILL SEE SOME POTENTIAL
FOR LIGHT ICE ACCUMULATIONS. AT THIS POINT...WILL CONTINUE TO
HIGHLIGHT THE ICE POTENTIAL IN THE HWO...AS IT IS 3RD PERIOD...AND
A TRACK THAT IS SLOWER COULD DELAY THE ONSET UNTIL LATER SAT NIGHT
INTO SUNDAY...THEREBY CHANGING P-TYPE POTENTIAL.

WITH THE SFC HIGH OVER THE WRN ATLANTIC AND AN INSITU-
WEDGE...LINGERING POCKETS OF FREEZING RAIN UNTIL ABOUT NOON OVER
THE VALLEYS NORTH OF ROANOKE...B4 WARM NOSE AND WEDGE START TO
SHRINK AND WARM THE SFC TEMPS ABOVE FREEZING. RAINFALL WILL MOVE
EAST OF THE AREA BY LATE SUNDAY AFTERNOON...AS THE LOW PRESSURE
SHIFTS OFF THE COAST. LINGERING MOISTURE ON THE BACK SIDE WITH
COLDER AIR WILL BRING A FEW RAIN/SNOW SHOWERS TO THE MTNS OF WV.

TEMPERATURES ARE GOING TO COOL DOWN SAT EVENING...THEN STEADY OUT
OR RISE TOWARD 12Z SUNDAY. SUNDAY TEMPS SHOULD HOLD STEADY IN THE
WEDGE ACROSS THE FOOTHILLS/SRN SHENANDOAH VALLEY INTO MIDDAY
SUNDAY WITH WARMING TEMPS ELSEWHERE. TRICKY FORECAST ON
HIGHS...BUT THINK COOLER THAN MOS THE WAY TO GO.

SUNDAY NIGHT...NOT EXPECTED MUCH WIND BEHIND THIS SYSTEM EITHER
THIS TIME...MAYBE 10-15 MPH. WARM ADV ACTUALLY BEGINS BEHIND THIS
BY SUNDAY NIGHT WELL IN ADVANCE OF NEXT SYSTEM...AND AS A RESULT
INCREASED THE LOWS FOR SUN NIGHT A FEW DEG. ANY LINGERING UPSLOPE
SHWRS IN FAR WEST QUICKLY FADE AS FLOW TURNS WEST OR WSW OVERNIGHT
AND ANTICYCLONIC FLOW ALOFT RETURNS. MOST OF THESE WILL BE RAIN
SHWRS GIVEN WARMING 850 TEMPS.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
RIDGING AT THE SURFACE AND ALOFT WILL INFLUENCE THE WEATHER FOR 
MONDAY AS SLIGHTLY DRIER AIR AND SUBSIDENCE ENTER THE AREA. A 
SURFACE LOW PRESSURE SYSTEM MOVES INTO THE GREAT LAKES WITH A COLD 
FRONT STRETCHING SOUTHWEST INTO ARKANSAS. THIS WILL PUSH EASTWARD 
MONDAY NIGHT INTO TUESDAY INCREASING MOISTURE OUT AHEAD OF THIS 
SYSTEM WITH THE SOUTHWESTERLY FLOW. MAINTAINED SLIGHT CHANCE POPS 
INCREASING TO CHANCE BY 12Z TUESDAY ACROSS THE FORECAST AREA. THE 
LATEST RUN OF THE ECMWF LOOKS TO BE A LITTLE SLOWER THAN THE GFS ON 
TIMING OF THE PRECIP. HAVE LEANED MORE TOWARD THE FASTER SOLUTION. 

WITH LOWS BELOW FREEZING...SNOW SHOWERS WILL SPREAD FROM NORTHWEST 
TO SOUTHEAST...MAINLY ALONG AND WEST OF THE BLUE RIDGE MOUNTAINS. 

GFS PROGS THE COLD AIR ADVECTION FILTERING IN TUESDAY AFTERNOON AS 
850 MB TEMPS FALL INTO THE RANGE OF +6 TO -6 FROM SOUTHEAST TO 
NORTHWEST. THE COLD AIR BANKS UP AGAINST THE APPALACHIAN MOUNTAINS 
OVERNIGHT WITH -12 IN SOUTHEAST WEST VIRGINIA. EXPECT ANOTHER NIGHT 
WITH LOWS IN THE UPPER TEENS TO LOWER 20S ONCE AGAIN WEDNESDAY 
NIGHT.  

SURFACE HIGH PRESSURE PUSHES INTO THE AREA IN THE WAKE OF THE COLD 
FRONT TUESDAY NIGHT INTO WEDNESDAY AND LASTING THROUGH THE END OF 
THE WEEK. COLD AIR WILL REMAIN IN PLACE THROUGH THURSDAY NIGHT WITH 
TEMPERATURES STAYING BELOW NORMAL. 
&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
VFR CONDITIONS WILL CONTINUE AT ALL AIRPORTS THROUGH FRIDAY NIGHT
UNDER DRY HIGH PRESSURE MOVING IN FROM THE SOUTHWEST. CENTER OF
HIGH REMAINS TO THE SOUTHWEST HOWEVER...AND STRONG WESTERLY
GRADIENT STILL EXISTS ALOFT TODAY. WESTERLY SFC WINDS WILL PICK
UP TO 10 TO 15 KNOTS BY 15Z...WITH GUSTS 20 TO 25 KNOTS. BY THIS
EVENING...SFC HIGH SETTLES IN MORE OVERHEAD AND MORE COMPLETE
DECOUPLING IS EXPECTED AT ALL SITES SO WINDS WILL DROP OFF TO
LIGHT WESTERLY ALL SITES. SOME VERY THIN CIRRUS POSSIBLE BY
MORNING...BUT NOT WORTHY OF MENTION IN TAFS.

VFR WEATHER WITH UNRESTRICTED FLIGHT CONDITIONS ARE EXPECTED OVER
ALL TERMINAL FORECAST SITES (KROA...KLYH...KDAN...KBLF...KLWB)
AGAIN SATURDAY...BUT THEN IS EXPECTED TO DETERIORATE SATURDAY
NIGHT INTO SUNDAY. AN AREA OF LOW PRESSURE IS EXPECTED TO DEVELOP
OVER THE GULF OF MEXICO SATURDAY...THEN SLIDE TO ALONG THE SOUTH
CAROLINA COAST BY SUNDAY. THIS WILL BRING LOWERING CIGS SATURDAY
NIGHT AND EVENTUALLY A WINTRY MIX OF PRECIPITATION BEFORE
DAYBREAK. THIS WILL BRING A RETURN OF IFR CONDITIONS FOR MUCH OF
SUNDAY. THE SYSTEM SHOULD EXIT THE REGION SUNDAY NIGHT WITH
IMPROVED FLIGHT CONDITIONS MONDAY. ANOTHER FRONT WILL AFFECT THE
REGION TUESDAY...AND MAY BRING RAIN...WITH A RETURN TO MVFR OR IFR
CONDITIONS.

&&

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

&&

$$
SYNOPSIS...SK/NONE
NEAR TERM...RCS
SHORT TERM...SK/WP
LONG TERM...REB
AVIATION...RCS