FXUS61 KRNK 141813
AFDRNK
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
113 PM EST MON DEC 14 2009
.SYNOPSIS...
HIGH PRESSURE WILL BUILD ACROSS THE REGION TODAY. A COLD FRONT
WILL SWEEP THROUGH THE AREA ON TUESDAY. HIGH PRESSURE RETURNS BY
MID WEEK...AND ITS INFLUENCE WILL CONTINUE INTO THE EARLY PART OF
THE WEEKEND.
&&
.NEAR TERM /THROUGH TONIGHT/...
STILL SHAPING UP TO BE A MILD DAY AS TEMPS 850-900 MB ARE BETW +10
TO +12 DEG C. KEY IS GETTING THIS WARM AIR TO MIX TO THE SURFACE.
HIGHS IN THE 50S TO AROUND 60 LOOK PROMISING. CLOUD COVER WILL BE
A BIT TRICKY. AND WHERE CLOUDS FORM OR ADVECT BACK INTO THE
AREA...THIS WILL CUT DOWN ON FULL INSOLATION AND MIXING POTENTIAL.
THERE IS QUITE A BIT OF LOW LEVEL CLOUD COVER OVER THE
CAROLINAS...AND THIS LOW LEVEL CLOUD DECK COULD EASILY SNEAK BACK
INTO THE SOUTHERN CWA PER INCREASING SOUTHERLY FLOW. HOPING THE
WESTERLY WIND AT 85H AND ABOVE WILL LIMIT THE NORTHWARD
DRIFT...BUT FOR THE MORNING UPDATE SKEWED FORECAST TO A LITTLE BIT
MORE CLOUD COVER FOR THE NC/VA BORDER COUNTIES.
TONIGHT CLOUDS WILL BE ON THE INCREASE AS A COLD FRONT APPROACHES
FROM THE WEST AND AN AREA OF LOW PRESSURE JUST MISSES THE REGION TO
THE SOUTH. AFTER MIDNIGHT...LOOK FOR FAR SOUTHERN AND FAR WESTERN
PARTS OF THE AREA TO STARTING SEEING SOME ISOLATED SHOWERS. FAVORED
LOWS ON THE MILD SIZE OF GUIDANCE.
&&
.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
WEAK COLD FRONT ENTERS SE WEST VA NEAR 12Z TUESDAY. MODELS CONTINUE
TO BACK OFF POPS...WITH MOISTURE SHALLOW AND NOT REACHING H7. DEEPER
MOISTURE MOVING THROUGH THE SOUTHEAST WILL BE CUTOFF BY VEERING
DOWNSLOPING SURFACE WINDS INTO THE AFTERNOON. ELEVATIONS OF SE WEST
VA AND EXTREME NW NC WILL CARRY THE HIGHEST POPS...ALBEIT STILL IN
THE CHC CATEGORY. ACTUALLY A RATHER SMALL WINDOW TUESDAY MORNING
WHEN THE BEST LIFT AND MOISTURE COINCIDE. THE NEW RIVER VALLEY INTO
THE LYH/FVX CORRIDOR COULD GO THROUGH THE DAY DRY.
ALTHOUGH WINDS BECOME NW TUESDAY NIGHT...MOISTURE IS VERY
SHALLOW...SO HARD TO SEE ANY ACCUMULATIONS EVEN ACROSS THE HIGHEST
SPOTS OF WESTERN GREENBRIER. JUST KEPT FLURRIES IN THE FORECAST. H85
TEMPS DROP FROM +5C TO ABOUT -5C ACROSS SE WEST VA DURING THE DAY
TUES...SO DID SKETCH IN A NONDIURNAL CURVE IN THOSE PARTS. WINDS MAY
GUST FROM 25-30 MPH AS THE COLDER AIR ARRIVES THROUGH THE REST OF
THE CWA LATE TUESDAY AND TUESDAY NIGHT.
SOME AMPLITUDE IN THE SOUTHERN STREAM WILL ALLOW MILDER AIR TO MIX
WITH THE BITTER COLD BEFORE IT ARRIVES ACROSS THE MIDDLE ATLANTIC.
BASICALLY A TEMPERATURE AND DEWPOINT FORECAST AFTERWARDS THROUGH
THURSDAY. CONSIDERING CONTINENTAL CANADIAN ORIGIN OF HIGH PRESSURE
ARRIVING WEDNESDAY AND WEDNESDAY NIGHT...DID TRY TO FOLLOW NAM12
DEWPOINTS...WHICH USUALLY PERFORM WELL WITH THIS TYPE OF AIRMASS.
HOWEVER...CONSIDERING THE VERY DRY AIR...LACK OF CLOUDS AND NEUTRAL
ADVECTION WITH H85 TEMPS AROUND -2C...DID WARM MAX T ON THURSDAY.
THE VERY DRY AIR WILL ALLOW TEMPS TO PLUMMET WEDNESDAY NIGHT...WITH
HIGH PRESSURE COVERING THE NW HALF OF THE REGION...A BIT OF A
GRADIENT REMAINING MAY SAVE THE SOUTHSIDE FROM REACHING THE LOWER
20S.
&&
.LONG TERM /FRIDAY THROUGH SUNDAY/...
DRY WEATHER CONTINUES THROUGH FRIDAY. THE MAIN CONCERN IN THE
EXTENDED WILL BE OVER THE WEEKEND WHEN A LOW PRESSURE SYSTEM
DEVELOPS AND BECOMES A COASTAL LOW SLIDING UP THE CAROLINAS AND
VIRGINIA. THE LATEST RUN OF THE ECMWF HAS THE LOW FARTHER OFFSHORE
AND SLOWER IN TIMING THAN THE GFS. COLD AIR ADVECTION WILL BE
TAKING PLACE SATURDAY ACROSS THE COUNTY WARNING AREA AND MOISTURE
WILL BE INCREASING. AT THIS TIME SOUNDING PROFILES SUPPORT BELOW
FREEZING TEMPERATURES WHICH FAVOR A SNOW P-TYPE IF WE DO RECEIVE
ANY PCPN. AGAIN BEING 6 TO 7 DAYS OUT...EXPECT MODEL RUNS TO
DIFFER SOMEWHAT AND AT LEAST MINOR CHANGES TO BE MADE...ESPECIALLY
WITH TIMING AND LOCATION.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
MAINLY VFR CONDITIONS THIS AFTERNOON. THERE IS A LAYER OF
CLOUDINESS THAT WILL DRIFT NORTH FROM THE CAROLINAS WITH CLOUD
BASES BETWEEN 025 AND 040 KFT AGL. AS SUCH TEMPO MVFR CONDITIONS
MAY BE OBSERVED ALONG AND EAST OF THE BLUE RIDGE...BUT FOR THE
SAKE OF SIMPLICITY KEPT CONDITIONS PREDOMINANTLY VFR WITH NO
TEMPO GROUPS.
FOR TONIGHT...THE TREND WILL LIKELY BE DOWN...WITH LOWERING CLOUD
BASES AHEAD OF AN APPROACHING COLD FRONT. SOME FOG IS
POSSIBLE...ESP EAST OF THE BLUE RIDGE...WHERE IFR CONDITIONS ARE
POSSIBLE...PERSISTING UNTIL THE FRONTAL PASSAGE EARLY TUESDAY MORNING.
A COLD FRONT WILL MOVE THROUGH THE REGION EARLY TUESDAY...BRINGING
A LOW THREAT OF PRECIPITATION AND MVFR TO IFR CONDITIONS IN THE
MOUNTAINS. ONCE THE FRONT PUSHES EAST OF THE MOUNTAINS...STRONG
DOWNSLOPE FLOW SHOULD DEVELOP WHICH SHOULD SCOUR ANY LOW
CLOUDINESS EAST OF THE MOUNTAIN. ALONG THE WINDWARD
SLOPES...CLOUDS WILL PERSIST...WITH STRONG COLD ADVECTION
RESULTING IN MOUNTAIN RAIN/SNOW SHOWERS.
COLD HIGH PRESSURE WILL BUILD OVER THE AREA TUESDAY NIGHT AND
WEDNESDAY WITH UNRESTRICTED FLIGHT CONDITIONS. AN UPPER LEVEL
DISTURBANCE WILL MOVE THROUGH THE OHIO VALLEY THURSDAY INTO FRIDAY
SPREADING CLOUDINESS BACK INTO THE MOUNTAINS WITH THE THREAT OF
SNOW SHOWERS.
&&
.RNK WATCHES/WARNINGS/ADVISORIES...
VA...NONE.
NC...NONE.
WV...NONE.
&&
$$
SYNOPSIS...DS
NEAR TERM...DS/PM
SHORT TERM...KM
LONG TERM...REB
AVIATION...PM
