FXUS61 KRNK 252036
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
336 PM EST FRI DEC 25 2009

.SYNOPSIS...
HIGH PRESSURE REMAINS WEDGED DOWN THE EAST SIDE OF THE
APPALACHIANS. WEAK LOW PRESSURE DEVELOPING IN THE NORTH CAROLINA
PIEDMONT WILL TRACK INTO EASTERN VIRGINIA BY SATURDAY MORNING.
COLDER HIGH PRESSURE WILL SLOWLY BUILD INTO THE REGION OVER THE
WEEKEND. 

&&

.NEAR TERM /THROUGH SATURDAY/...
ALL OBSERVATIONS INDICATE THAT SFC TEMPS HAVE FINALLY CREPT ABOVE
32 DEGREES. HAVE CANCELED THE REMAINING ICE STORM/FREEZING RAIN
ADVISORIES. OBSERVATIONS ALSO INDICATE THAT THE STRONGER
WINDS HAVE SUBSIDED...SO THINK WE CAN LET THE HIGH WIND
WARNINGS/WIND ADVISORIES EXPIRE AT 400 PM. WEAK LOW PRESSURE
DEVELOPING ALONG THE WARM FRONT IN THE NC PIEDMONT WILL LIFT INTO
EASTERN VA ALONG THE EDGE OF THE CAD AREA. THIS WILL KEEP LIGHTER
RAIN/DRIZZLE IN THE PIEDMONT AREAS WELL INTO TONIGHT...PARTICUALRY
LYH EASTWARD. SHOULD ALSO SEE AREAS OF FOG DEVELOP. AS FOR THE
FLOOD WATCH...THE HEAVIER RAIN IS BEGINNING TO PUSH EAST OF THE
FORECAST AREA. WE HAVE CHECKED AROUND...AND THERE ARE ONLY MINOR
POOR DRAINAGE FLOOD PROBLEMS...NO CREEKS OUT OF THEIR BANKS. RADAR
ESTIMATES A GOOD 1.5 INCHES OF RAIN ACROSS THE SRN CWA...SO CREEKS
AND RIVERS WILL SEE STRONG RISES. WILL LET THE FLOOW WATCH
EXPIRE...AND ISSUE A SPECIAL WEATHER STATEMENT FOR MINOR POOR
DRAINAGE PROBLEMS. A FLOOD WARNING CONTINUES FOR SOUTH BOSTON ON
THE DAN RIVER. 

WITH COLD ADVECTION LAGGING AND THE OCCLUDED FRONT NOT COMING
THROUGH MOST OF THE AREA UNTIL MORNING...I KEPT OVERNIGHT LOWS
CLOSER TO THE WARMER MAV. SATURDAY WILL BE A MILD DAY FOR ALL BUT
THE WESTERN MTNS AS WELL...WITH MORE OF A WEST-SOUTHWEST FLOW OF
COLD ADVECTION JUST GRADUALLY BRINGING COLDER AIR INTO TEH AREA. I
KEPT HIGHS SATURDAY ON THE WARM SIDE OF GUIDANCE...ESPECIALLY IN
THE PIEDMONT. 

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
COLD FRONT WILL CONTINUE PUSHING EAST OVER THE ATLANTIC AS SURFACE 
RIDGING NOSES IN FROM THE SOUTHWEST INTO THE WESTERN PORTION OF THE 
FORECAST AREA. COLDER DRIER AIR WILL FILTER FROM THE WEST ACROSS THE 
REGION WITH 850H TEMPERATURES BELOW 0 DEGREES C THROUGH MONDAY NIGHT. 
THE COLDEST AIR PUNCHES IN WITH -12 DEGREES C AT 850H IN SOUTHEASTERN 
WEST VIRGINIA SUNDAY NIGHT. MAX TEMPERTURES WILL RANGE FROM THE MID 
30S WEST OF THE BLUE RIDGE MOUNTAINS TO NEAR 50 IN THE PIEDMONT. 
WITH COLD AIR ADVECTION IN COMBINATION WITH THE CLOUDS 
THINNING...LOW TEMPERATURES WILL DROP INTO THE UPPER TEENS TO LOWER 
20S IN THE MOUNTAINS WITH MID 20S EAST SUNDAY AND MONDAY NIGHT.

A DISTURBANCE WILL APPROACH THE AREA SUNDAY NIGHT WITH A 
SOUTHWESTERLY FLOW OUT AHEAD INCREASING MOISTURE INTO THE WESTERN 
ZONES. AS THE WAVE APPROACHES...WINDS WILL VEER TOWARD THE WEST TO 
NORTHWEST GIVING WAY TO AN UPSLOPE COMPONENT. CONTINUE SLIGHT CHANCE 
POPS IN THE FAVORABLE WESTERN UPSLOPE REGIONS BUT THE MODELS SEEM TO 
BE SLOWING DOWN THE TIMING OF THE PRECIP WHICH MAY DELAY THE ONSET 
UNTIL LATER SUNDAY NIGHT. WITH TEMPERATURES BEING BELOW 
FREEZING...PRECIP WILL BEGIN AS ALL SNOW AND WILL CONTINUE THROUGH 
MONDAY NIGHT. 

850H WINDS INCREASE TO 40 TO 45 KNOTS IN WHICH THE RIDGETOPS COULD 
BECOME GUST TO 20 TO 25 MPH MONDAY MORNING AND LAST THROUGH THE DAY.

&&

.LONG TERM /TUESDAY THROUGH THURSDAY/...
MID-WEEK PERIOD LOOKS TRANQUIL WITH SURFACE HIGH PRESSURE CENTERED 
ACROSS THE MID-MISSISSIPPI VALLEY EARLY TUESDAY SLIDING EAST TO THE 
MID-ATLANTIC BY WEDNESDAY. CORE OF THE COLDEST AIR REMAINS WELL TO 
THE NORTH ACROSS NORTHERN NEW ENGLAND BUT WITH CLEAR SKIES AND H85 
TEMPS -2 TO -6C SHOULD SEE SEASONABLY CHILLY TEMPS TUE AND WED 
MORNINGS...GENERALLY UPPER TEENS WEST TO MID-20S EAST. HIGHS ALSO 
NEAR TO SLIGHTLY BLO LATE DEC NORMALS RANGING FROM LOW 30S NW TO 
MID-40S SE. BOTH GFS/ECMWF TRY TO DEVELOP LOW PRESSURE ALONG THE 
GULF COAST BY EARLY THU AS HIGH PRESSURE DEPARTS THE EAST COAST AND 
A SHORT-WAVE ROUNDS THE BASE OF THE LONG-WAVE TROUGH CENTERED 
SOMEWHERE IN THE CENTRAL CONUS. THE LATEST RUNS...12Z GFS AND 00Z 
EC...BOTH PRODUCE AN INVERTED TROUGH ALONG THE SOUTHEAST COAST BY 
LATER THU AND THEN WEAK LOW PRESSURE OFF THE CAROLINA COAST. WEAK 
LOW PRESSURE ALONG THE COAST IS ALSO SHOWN BY NEARLY ALL THE GFS 
ENSEMBLES WITH THE BULK OF THE PRECIPITATION SOUTHEAST OF THE 
FORECAST AREA. HOWEVER THE GENERAL PATTERN REMAINS SOMEWHAT 
FAVORABLE FOR MORE SIGNIFICANT COASTAL DEVELOPMENT LATE IN THE WEEK 
AND RUN TO RUN MODEL FLUCTUATIONS ARE TO BE EXPECTED IN FUTURE. FOR 
NOW HAVE SIMPLY MAINTAINED SLIGHT CHANCE OR CHANCE POPS FROM EARLY 
THURSDAY THROUGH THE END OF THIS FORECAST CYCLE. 

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
FREEZING RAIN HAS ENDED AT ALL WFO RNK TERMINAL SITES...BUT CIGS
HAVE LOWERED TO IFR EAST OF THE MTNS AT ROA...LYH AND DAN. LOWERED
CIGS ARE ALSO EXPECTED AT BLF AND LWB...BUT THEY WILL BE VARYING
HIGHER AT TIMES THE REST OF THE AFTERNOON. MAIN ISSUE THROUGH 21
TO 22Z WILL BE LLWS. A VERY STRONG LLJ REMAINS OVER THE
AREA...THOUGH SHOULD BE STARTING TO DECREASE IN SPEED REST OF THE
AFTERNOON. HOWEVER...WITH SFC WINDS MAINLY LIGHT AT ALL SITES EXCEPT
FOR BLF...THE SHEAR MAGNITUDE WILL BE GREAT...POSSIBLY UP TO 40
KNOTS IN THE LOWEST 2000 FEET. 

RAIN WILL BE LIFTING NE AWAY FROM THE REGION THIS EVENING...AND
ALL SITES ARE EXPECTED TO DROP TO IFR OR EVEN LIFR WITH A LIGHTER
WIND FLOW AND ABUNDANT LOW LEVEL MOISTURE. THE IFR CONDITIONS WILL
LIKELY HANG ON UNTIL AROUND/AFTER 12Z SATURDAY. VFR CONDITIONS ARE
THEN EXPECTED AT ALL SITES BY 18Z SATURDAY.

THERE WILL BE TYPICAL MVFR TO LOCALIZED IFR RESTRICTIONS
CONTINUING IN THE UPSLOPE AREAS WEST OF THE BLUE RIDGE (KBLF/KLWB)
DUE TO STRATOCUMULUS AND SCATTERED SNOW SHOWERS THROUGH SUNDAY.

&&

.EQUIPMENT...
USE THE WIND OBSERVATION AT ROA WITH CAUTION. AN ERROR HAS BEEN
REPORTED WITH THE WIND SENSOR...IT MAY BE FROZEN. IF THE SENSOR
HAS FROZEN IT WILL CONTINUE TO REPORT A CALM WIND UNTIL THE ICE IS
BROKEN OFF OR THE ICE MELTS OFF THE SENSOR.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...WIND ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR VAZ011>014-
     016>020-022>024-032>035.
     HIGH WIND WARNING UNTIL 4 PM EST THIS AFTERNOON FOR 
     VAZ007-009-010-015. 
     FLOOD WATCH UNTIL 4 PM EST THIS AFTERNOON FOR
     VAZ032-043-044- 058. 
NC...WIND ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR NCZ002. 
     HIGH WIND WARNING UNTIL 4 PM EST THIS AFTERNOON FOR 
     NCZ001-018. 
     FLOOD WATCH UNTIL 4 PM EST THIS AFTERNOON FOR 
     NCZ003>006-019- 020. 
WV...WIND ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR WVZ044. 
     HIGH WIND WARNING UNTIL 4 PM EST THIS AFTERNOON FOR 
     WVZ042-043- 045.

&&

$$
SYNOPSIS...JJ
NEAR TERM...JJ
SHORT TERM...REB
LONG TERM...PC
AVIATION...AMS/JJ
EQUIPMENT...