FXUS61 KRNK 260458
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
1158 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/...
FOG HAS BECOME DENSE IN SPOTS THROUGHOUT THE CWA BUT WEATHER CAMS
DEPICT PATCHY TO AREAS AT BEST. FLUCTUATIONS IN WIND SPEED WILL
CAUSE THE FOG TO VARY IN DENSENESS. THEREFORE...HAVE ELECTED TO
COVER THIS WITH A SPECIAL WEATHER STATEMENT. LIGHT RAIN WILL EXIT
TO THE NORTH OVERNIGHT WITH THE CAA ARRIVING FROM THE SOUTHWEST-
WEST TOWARD DAWN. SFC TEMPS AT OR BELOW FREEZING TOWARD DAYBREAK
WILL ALSO CAUSE BLACK ICE CONCERNS. MENTIONED THIS ALSO IN THE SPS.
OTHERWISE...KEPT LOWS CLOSE TO THE PREVIOUS FORECAST. DRIER AIR
WILL START TO WORK IN FROM THE SW OVERNIGHT...AND COULD CAUSE
CIGS/VSBYS TO RISE IN THE NC MTNS/SW VA MTNS BY 12Z.
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 FRIDAY/...
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 /06Z SATURDAY THROUGH WEDNESDAY/...
ALL TAF SITES TONIGHT WILL REMAIN IN THE DRINK...IN TERMS OF LOW
CIGS AND/OR VSBYS. THESE CONDITIONS MAY FLUCTUATE FROM TIME TO
TIME...BUT AS VSBYS DROPS...CIGS MAY RISE SOME...AND VICE VERSA.
SO OVERALL...LOOKING AT LIFR TO VLIFR THROUGH ABOUT 12-16Z...WITH
IMPROVEMENTS TO VFR BY MIDDAY.
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....OTHERWISE...LOOKING AT VFR INTO EARLY NEXT WEEK.
&&
.HYDROLOGY...
STILL GETTING SOME RISES ALONG THE ROANOKE RIVER UPSTREAM OF
WALNUT STREET. HOWEVER...ONLY EXPECTING THE ROANOKE RIVER AT
WALNUT ST TO GET JUST ABOVE THE ACTION STAGE OF 6 FEET BY
DAWN...AS MAIN PRECIP FELL DOWNSTREAM AND SOUTH OF THE AREA. THE
MAIN CHANGE WAS TO INCREASE THE RISE AT SOUTH BOSTON AND PACES.
PACES LOOKS TO REACH CLOSE TO FLOOD STAGE SATURDAY AFTN...WHILE
SOUTH BOSTON FLOODS BUT REMAINS BELOW THE MODERATE FLOOD CATEGORY
OF 25 FEET.
&&
.CLIMATE...
RECORD PRECIPITATION HAS BEEN SET AT BOTH ROANOKE AND BLACKSBURG
FOR THE MONTH OF DECEMBER. SEE THE LATEST RER FOR DETAILS. THE 1.42
INCHES OF PRECIP TODAY WAS THE 2ND MOST PRECIP FOR CHRISTMAS. THE
FIRST BEING 1.5 INCHES IN 1969.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...JJ/WP
NEAR TERM...JJ/WP
SHORT TERM...REB
LONG TERM...PC
AVIATION...JJ/WP
HYDROLOGY...
CLIMATE...
