Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 151111
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
711 AM EDT MON SEP 15 2014

.SYNOPSIS...
HIGH PRESSURE OVER THE AREA THIS MORNING WILL SHIFT EAST AND
OFFSHORE THIS AFTERNOON BRINGING WARMER TEMPERATURES AS LIGHT
RETURN SOUTHWEST FLOW DEVELOPS. THE NEXT COLD FRONT MOVES THROUGH
LATER TONIGHT RESULTING IN A FEW SHOWERS FOLLOWED BY DRIER AND
COOLER WEATHER INTO MID WEEK. STRONG HIGH PRESSURE WILL BUILD
NORTH OF THE AREA FOR THE REST OF THE WEEK KEEPING RATHER COOL BUT
OVERALL DRY WEATHER IN PLACE.
&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 230 AM EDT MONDAY...

WEDGE REMAINS IN PLACE EARLY THIS MORNING WITH HIGH PRESSURE STUCK
ALONG THE EASTERN SLOPES AND A LIGHT EAST TO SE TRAJECTORY IN PLACE.
THIS SHOULD HELP KEEP LOW CLOUDS AND DENSE FOG IN PLACE INTO THE
MORNING WITH JUST SOME SPOTTY -DZ OR SPRINKLES SOUTH.

CAD FINALLY STARTS TO BREAK DOWN THIS AFTERNOON AS THE SURFACE HIGH
SHIFTS EAST AHEAD OF THE NEXT UPSTREAM 5H TROUGH AND ITS WEAK
ASSOCIATED COLD FRONT. DEVELOPING WEAK RETURN SOUTH/SW FLOW AHEAD OF
THE FRONT LOOKS TO START SCOURING OUT SOME OF THE LOW LEVEL MOISTURE
BUT TO WHAT DEGREE REMAINS IN QUESTION. THINK AREAS ACROSS THE FAR
NORTH IN THE WAKE OF A PASSING WAVE ALOFT THIS MORNING PER VAPOR LOOP
LIKELY TO HAVE MORE SUN WHILE ANY HEATING ELSW WILL ONLY LEAD TO MORE
CU DEVELOPMENT. THUS KEEPING IT PARTLY/MOSTLY CLOUDY WITH PWATS STILL
RATHER MOIST. SHOWER CHANCES ALSO IFFY GIVEN LITTLE FORCING AND LACK OF
SUSTAINED HEATING FOR THE MOST PART. MOST GUIDANCE HAS CUT WAY BACK ON
POPS/QPF TODAY WITH ONLY A FEW INCLUDING THE SREF SHOWING SOME
DEVELOPMENT SW TIER WHERE ANOTHER WEAK IMPULSE ALOFT ARRIVES LATE. NAM
ALSO SHOWS SOME MODEST CAPES OF 500-1K J/KG FROM THE NEW RIVER SOUTH
INTO THIS EVENING ALONG A WEAK 85H THETA-E RIDGE BUT LIKELY OVERDONE
WITHIN THE CURRENT COOL POOL. THUS CUT BACK POPS TO MOSTLY 20/30 TYPE
COVERAGE THIS AFTERNOON/EVENING WITH BEST CHANCES SW AND LEAST OVER THE
NE. LEFT SOME ISOLATED THUNDER MENTION IN LATER ON SOUTH BUT THAT MIGHT
BE GENEROUS AS WELL.

TEMPS MAY FINALLY GET OUT OF THE 60S GIVEN A BUMP IN 85H VALUES
UNDER WEAK SW FLOW. HOWEVER IF INSOLATION IS LESS THEN VALUES
CLOSER TO THE COOLER EC 2M TEMPS LOOK BEST AND WERE FOLLOWED
ESPCLY EAST WHERE CLOUDS MAY LINGER LONGER.

WEAK FRONT ZIPS ACROSS FROM THE NW THIS EVENING WITH THE AREA AGAIN
BASICALLY IN BETWEEN DEEPER MOISTURE WITH THE RESIDUAL BOUNDARY TO THE
SOUTH AND LIMITED LIFT WITH THE UPSTREAM FRONT. GIVEN AN OVERALL
WESTERLY TRAJECTORY...DOUBTING MUCH IN THE WAY OF OVERALL SHOWER
COVERAGE AFTER EARLY THIS EVENING WITH PERHAPS THE WESTERN SLOPES
HAVING THE BEST SHOT LATE AS UPSLOPE INCREASES. THUS THINKING OF GOING
FOR JUST ISOLATED COVERAGE AFTER SUNSET AND BETTER CHANCES FAR NW AFTER
MIDNIGHT WITH LITTLE POP ELSW LATE BEHIND THE FRONT. LOWS 50S WEST TO
LOW 60S EAST AS A NEW ROUND OF COOL ADVECTION STARTS TO ARRIVE LATE.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/...
AS OF 315 AM EDT MONDAY...

A COLD FRONT WILL HEAD SOUTH OF THE REGION DURING THE DAY TUESDAY.
FORECAST 850 MB NORTHWEST WINDS BEHIND THE FRONT SHOULD YIELD
SURFACE GUSTS OF 15 TO 20 MPH ACROSS THE MOUNTAINS DURING THE
MORNING HOURS. ALSO...ENOUGH RESIDUAL MOISTURE AND UPSLOPE FLOW WILL
HELP MAINTAIN SOME ISOLATED SHOWERS ACROSS PARTS OF SOUTHEAST WEST
VIRGINIA...NEIGHBORING COUNTIES OF SOUTHWEST VIRGINIA...AND THE
NORTHERN MOUNTAINS OF NORTH CAROLINA PRIMARILY DURING THE MORNING AS
WELL.

TUESDAY NIGHT THROUGH THURSDAY NIGHT...A BROAD UPPER TROUGH IS
FORECAST TO BECOME POSITIONED ACROSS THE U.S. EAST COAST. SURFACE
HIGH PRESSURE WILL BUILD OVER PENNSYLVANIA...AND AN ASSOCIATED LEE
SIDE TROUGH WILL EXTEND SOUTH THROUGH OUR REGION. WHILE THE FORECAST
WILL BE A DRY ONE FOR MUCH OF THE REGION...LOW LEVEL FLOW WILL
GRADUALLY TAKE ON PRIMARILY AN E-SE COMPONENT WHICH WILL POOL
MOISTURE INTO THE CREST OF THE BLUE RIDGE...ALLOWING FOR THE
POTENTIAL FOR SOME UPSLOPE LIGHT RAIN SHOWERS IN THE NORTHERN
MOUNTAINS AND FOOTHILLS OF NORTH CAROLINA AND NEIGHBORING PARTS OF
SOUTHWEST VIRGINIA. THIS E-SE FETCH MAXIMIZES...AND POTENTIALLY TAPS
SOME ATLANTIC MOISTURE ON THURSDAY AND THURSDAY NIGHT. THIS WOULD
ALLOW FOR A BIT MORE OF THE REGION...ESPECIALLY ALONG AND NEAR THE
CREST OF THE BLUE RIDGE...TO EXPERIENCE SOME ISOLATED SHOWERS. CANNOT
RULE OUT SOME ISOLATED THUNDERSTORMS BOTH TUESDAY AFTERNOON AND
WEDNESDAY AFTERNOON IN THE NC MOUNTAINS.

TEMPERATURES WILL TREND COOLER DURING THIS PORTION OF THE FORECAST
BEHIND THE COLD FRONT PASSAGE AND AS DRIER DEW POINT AIR SETTLES
INTO THE REGION.

&&

.LONG TERM /FRIDAY THROUGH SUNDAY/...
AS OF 345 PM EDT SUNDAY...

FOR MOST OF THE LONG TERM PERIOD A BROAD UPPER TROF WILL CONTINUE TO
HOLD OVER THE EASTERN U.S. WITH SFC HIGH PRESSURE EXTENDING FROM THE
NORTHEAST THROUGH THE MID-ATLANTIC...KEEPING A WEDGE IN PLACE
THROUGH THE PERIOD.

A REINFORCING SHOT OF DRIER AIR ARRIVES BY FRIDAY AS A NORTHERN
STREAM WAVE BRIEFLY AMPLIFIES THE UPPER TROF. ECMWF/GFS ENSEMBLE
MEANS AND DETERMINISTIC RUNS NOW SHOW AN UPPER RIDGE TRYING TO
BUILD LATE IN THE LONG TERM PERIOD (SATURDAY/SUNDAY) WHICH WILL
WEAKEN THE WEDGE OF HIGH PRESSURE AT THE SFC AND ALLOW TEMPS TO
MODERATE.

UNTIL THEN...TEMPS WILL BE BELOW NORMAL AND MORNING LOWS IN THE 40S
WILL BE COMMON FOR MANY MOUNTAIN VALLEY LOCATIONS.

OUTSIDE OF UPSLOPE SHOWERS IN THE SOUTHERN BLUE RIDGE/NW NC
MOUNTAINS AND FOOTHILLS...MOST AREAS SHOULD REMAIN DRY.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
AS OF 700 AM EDT MONDAY...

AREAS OF IFR/LIFR IN FOG/STRATUS WILL PERSIST IN SPOTS ESPCLY
ACROSS THE SE WVA LOCATIONS INTO MID MORNING. MVFR CIGS ALONG
WITH SPOTTY MVFR VSBYS WILL ALSO FILL BACK IN ALONG THE BLUE RIDGE
EARLY THIS MORNING BEFORE HEATING AND MIXING STARTS TO LIFT CIGS
AND SCOUR OUT ANY LEFTOVER FOG.

ONCE THE FOG AND STRATUS LIFT...PERHAPS NOT UNTIL MIDDAY IN
SPOTS...CEILINGS AND VISIBILITIES WILL IMPROVE AS THE FLOW TURNS
MORE SW. EXPECT MOST TO PUSH INTO VFR DURING THE AFTERNOON WITH CU
BASES BETWEEN 4-5K FT WHILE ANY SHRA LOOKS TOO ISOLATED TO INCLUDE
FOR NOW. WEAK COLD FRONT SLIDES THROUGH MONDAY EVENING WITH AGAIN
MOSTLY ISOLATED SHOWERS BUT LIKELY ENOUGH WESTERLY FLOW TO KEEP
THINGS MOSTLY VFR DURING THE EVENING. POTENTIAL FOR LOWER CIGS TO
DEVELOP...MAINLY KBLF/KLWB...LOOKS TO COME LATER TONIGHT WITH
INCREASING UPSLOPE FLOW AND PERHAPS A FEW MORE SHOWERS AROUND.
SOME POTENTIAL TO ALSO SEE FOG REDEVELOP ACROSS THE EAST AS WELL
DESPITE THE FRONTAL PASSAGE GIVEN LIGHT WINDS AND LINGERING
MOISTURE SO INCLUDED A LATE NIGHT VSBY REDUCTION OUT EAST
EXCLUDING KROA OTRW SHOULD REMAIN VFR OUTSIDE OF FOG.

EXTENDED AVIATION DISCUSSION...

UPSLOPE MOISTURE MAY PERSIST INTO TUESDAY ALONG THE WESTERN SLOPES
WHILE EXPECT BRIEF DOWNSLOPE TO BRING MAINLY VFR ELSW INTO TUESDAY
AFTERNOON AS WEAK HIGH PRESSURE BUILDS IN.

BROAD UPPER TROUGH REMAINS IN PLACE ACROSS THE EASTERN STATES FOR
THE REMAINDER OF THE WEEK ALLOWING A LARGE AREA OF HIGH PRESSURE
TO BUILD SOUTH FROM THE GREAT LAKES FOR MID WEEK BEFORE WEDGING IN
FROM OFF THE MID ATLANTIC COAST BY THE WEEKEND.

THIS SHOULD PUSH THE PESKY DEEP MOISTURE FURTHER SOUTH AWAY FROM
THE REGION. HOWEVER BIGGER CONCERN WILL BE WITH TRAPPED RESIDUAL
LOW LEVEL MOISTURE THAT MAY KEEP SOUTHERN/WESTERN LOCATIONS STUCK
IN PERIODS OF MVFR CIGS ESPCLY WEDNESDAY INTO FRIDAY AS THE LOW
LEVEL EAST/SE FLOW TAKES SHAPE.

&&

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

&&

$$
SYNOPSIS...JH/PH
NEAR TERM...JH
SHORT TERM...DS
LONG TERM...PH
AVIATION...JH


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