FXUS61 KRNK 262036
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
336 PM EST SAT DEC 26 2009
.SYNOPSIS...
A STRONG LOW IN THE MIDWEST WAS CENTERED OVER EASTERN IOWA. A
WEAKER COASTAL LOW WILL MOVE NORTH TOWARD NEW ENGLAND TONIGHT WHILE
THE MID WEST LOW TRACKS TOWARD UPPER MICHIGAN. WEAK...BUT COLDER
HIGH PRESSURE WILL BUILD INTO THE MID ATLANTIC REGION TONIGHT AND
SUNDAY.
&&
.NEAR TERM /THROUGH SUNDAY/...
THICK JET ENHANCED CIRRUS ACROSS THE SERN HALF OF THE CWA WILL
SLOWLY SHIFT TO OUR EAST TONIGHT. ONCE THE CWA CLEARS OUT...WEAK
HIGH PRESSURE WILL BE OVER THE AREA AND THERE SHOULD BE GOOD
RADIATION CONDITIONS. EXCEPTION WILL BE HIGHER ELEVATIONS...WHERE
STRONGER SW FLOW AROUND THE MASSIVE UPPER LOW NOW OVER WISC WILL
KEEP RIDGES MIXED. I HAVE GONE A LITTLE COOLER THAN GUIDANCE FOR
LOW TEMPS MOST LOCATIONS.
SUNDAY...THE UPPER LOW DRIFTS EASTWARD...AND COLDER AIR CONTINUES
TO FILTER INTO THE AREA. OVERALL..HIGHS SHOULD BE A FEW DEGREES
COOLER THAN TODAY.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
AN UPPER LEVEL LOW WILL SWING THROUGH THE GREAT LAKES REGION
SUNDAY NIGHT...WITH A STRONG SHORT WAVE MOVG THRU THE CENTRAL
APPLNS...AS THE FORECAST AREA CATCHES THE SOUTHERN PERIPHERY.
SOUTHWEST WINDS AHEAD OF THE SURFACE WAVE INCREASES MOISTURE AND AS
WINDS TURN TOWARD A WEST NORTHWEST FLOW...THIS WILL ENHANCE THE
UPSLOPE COMPONENT AND BRING SNOW SHOWERS SUNDAY NIGHT/MONDAY.
THE LATEST MODEL RUNS HAVE THE PRECIP HANGING IN THROUGH TUESDAY
MORNING IN THE FAVORABLE WESTERN UPSLOPE REGIONS. MAINTAINED THE
LIKELY POPS IN THE UPSLOPE AREAS OF SE WV...AND CATEGORICAL WESTERN
GREENBRIER THROUGH EARLY MONDAY AFTERNOON. THEN HAVE POPS TAPERING
OFF FROM EAST TO WEST BY MONDAY NIGHT. HIGHEST POPS WILL REMAIN IN
THE NORTHERN TIP OF GREENBRIER WHICH MAY LAST THROUGH THE DAY
MONDAY. PRECIP WILL BE LIGHT THOUGH...ACCUMULATIONS SHOULD BE JUST A
FEW INCHES AT BEST.
MODELS PROG 850H WINDS INCREASING TO 50 KNOTS FROM MONDAY AFTERNOON
INTO MONDAY NIGHT. WINDS ON RIDGETOPS COULD GUST TO 20 TO 30 MPH
LATE MONDAY AND LASTING THROUGH TUESDAY MORNING.
HIGH PRESSURE WILL SLIDE EAST ACROSS THE REGION ON TUESDAY WHICH
WILL ALLOW THE WINDS TO SUBSIDE FAIRLY QUICKLY.
&&
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
SURFACE HIGH PRESSURE EXPECTED TO BE IN CONTROL ACROSS THE EASTERN
SEABOARD AT THE OUTSET OF THE EXTENDED PERIOD BUT CHANGES WILL BE IN
OFFING AFTER ABOUT WED. OPERATIONAL GFS AND GFS ENSEMBLES STILL
CARRYING ONLY A WEAK FLAT WAVE OUT OF THE WESTERN GOMEX MID- TO LATE
WEEK WITH THE BULK OF THE PRECIPITATION ALONG AND THEN EAST OF THE
CAROLINA COAST AND VERY LITTLE REACHING BACK THIS FAR WEST.
ECMWF HOWEVER...IS CONSIDERABLY SLOWER AND MORE DEVELOPED WITH A
CLOSED SURFACE LOW OVER THE NE GULF BY LATER ON THURSDAY WHICH IT
MOVES RAPIDLY NORTHEAST THE VA CAPES BY 12Z FRIDAY. WITH NO REAL
BLOCKING SURFACE HIGH OVER NEW ENGLAND THAT SEEMS REASONABLE...BUT
WOULD MEAN A BETTER CHANCE FOR PRECIPITATION HERE...POTENTIALLY WINTRY
THU INTO FRI. AGAIN THE LACK OF A SURFACE HIGH AND STRONG WEDGE OF
COLD AIR WOULD MITIGATE AGAINST A PURELY SNOW OR FROZEN EVENT. ECMWF
H85 TEMPS FLIRTING WITH 0C AT THE ONSET OF PRECIP BUT RISE TO THE +1
TO +5C RANGE ACROSS THE CWA...SO IT COULD WIND UP MAINLY A RAIN
EVENT. AT THIS POINT HAVE INCREASED GRID POPS TO HIGHER CHANCE ON
THURSDAY WITH MAINLY SNOW IN THE WEST...A MIX IN BETWEEN AND RAIN IN
THE SOUTHEAST. BEYOND 12Z FRIDAY EC MODEL SHOWS DEEPENING AND
PHASING OF A COASTAL CYCLONE WHICH WOULD POTENTIALLY BRING A MAJOR
STORM TO NEW ENGLAND AND OR PENNSYLVANIA BUT LEAVE THIS AREA MAINLY
IN THE BACKLASH WITH STRONG COLD AIR ADVECTION...THE USUAL MOUNTAIN
SNOW SHOWERS AND MUCH COLDER AIR DROPPING THROUGH THE OHIO VALLEY
INTO THE CWA DURING THE DAY SATURDAY. H85 TEMPS FALL TO -14 TO -16C
ON BOTH GFS AND EC MODELS SO CONFIDENCE IN A SHIFT TO MUCH COLDER
REGIME IS HIGHER THAN IN THE EVENTUAL OUTCOME OF A STORM.
&&
.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
HIGH PRESSURE WILL BE RIDGING INTO THE AREA THIS AFTERNOON AND
TONIGHT. WITH THE EXCEPTION OF SOME FOG IN THE PIEDMONT AREAS...
VFR CONDITIONS ARE EXPECTED THROUGH THE NEXT 24 HOURS. LYH AND DAN
WILL LIKELY SEE SOME MVFR FOG...AND HAVE A CHANCE FOR A FEW HOURS
OF IFR BEFORE DAYBREAK.
ON SUNDAY NIGHT THROUGH MONDAY NIGHT AN UPPER TROF WILL BRING
COLDER AIR BACK INTO THE REGION WITH UPSLOPE LOW LEVEL WINDS IN
THE MOUNTAINS. SNOW SHOWERS ARE EXPECTED IN BLF AND LWB WHICH WILL
RESULT IN MVFR TO OCCASIONALLY IFR CEILINGS AND VISIBILITIES. AT
THIS TIME SNOWFALL AMOUNTS ARE EXPECTED TO REMAIN LIGHT.
EAST OF THE BLUE RIDGE WILL BE VFR INTO WEDNESDAY.
A LARGE STORM SYSTEM MAY IMPACT THE REGION AS EARLY AS
THURSDAY...BRINGING MVFR OR IFR CONDITIONS.
&&
.HYDROLOGY...
FLOOD WARNINGS REMAIN IN EFFECT FOR DANVILLE...PACES AND SOUTH
BOSTON ON THE DAN RIVER...AND ALSO RANDOLPH ON THE ROANOKE RIVER.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...JJ
NEAR TERM...JJ
SHORT TERM...REB
LONG TERM...PC
AVIATION...AMS/JJ
HYDROLOGY...
