Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 210824
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
424 AM EDT SUN SEP 21 2014

.SYNOPSIS...
LOW PRESSURE WAS OVER MICHIGAN WITH A COLD FRONT TRAILING INTO THE
MID MISSISSIPPI VALLEY. THIS FRONT WILL MOVE EAST TODAY AND
TONIGHT...AND WILL REACH THE EAST COAST BY MONDAY MORNING. MONDAY
THROUGH THURSDAY...A LARGE HIGH PRESSURE SYSTEM WILL COVER MUCH OF
THE EASTERN UNITED STATES.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 400 AM SUNDAY...

SATELLITE PICTURES AND SURFACE OBSERVATIONS SHOWED THAT FOG HAD
DEVELOPED IN THE NEW AND GREENBRIER RIVER VALLEYS THIS MORNING.
THE FOG WILL LIFT SHORTLY AFTER SUNRISE.

TIMING OF THE FRONT REMAINS SIMILAR IN THE GUIDANCE AS PAST FEW
RUNS. BULK OF SHOWERS AND THUNDERSTORMS WILL COME THROUGH THE
FORECAST AREA BETWEEN 2PM/18Z AND 8PM/00Z. AMOUNT OF INSTABILITY
THIS AFTERNOON WILL DEPEND ON HOW MUCH HEATING THERE IS...HOW FAST
THE CLOUDS ARRIVE FROM THE WEST. MODELS HAVE ENOUGH CAPE AND
SURFACE HEATING TO SUPPORT THUNDERSTORMS. MODELS ALSO CONFINE A
MAJORITY OF THE PRECIPITATION TO ALONG AND WEST OF THE BLUE RIDGE.
THIS SEEMS REASONABLE WITH THE LOW LEVEL WINDS STARTING FROM THE
NORTH THIS MORNING AND BACKING TO THE WEST AHEAD OF THE FRONT AS
HIGH PRESSURE OVER THE AREA WEAKENS.

THE FRONT COMES THROUGH THE FORECAST AREA BETWEEN 00Z/8PM AND
06Z/2AM. DECENT PRESSURE RISES BEHIND THE FRONT WITH 850 MB
TEMPERATURES DROPPING TO AROUND +6 IN SOUTHEAST WEST VIRGINIA BY
MONDAY MORNING.

EXPECTING SOME LOW LEVEL MOISTURE IN THE WESTERN UPSLOPE AREA
AFTER MIDNIGHT...BUT BUFKIT FORECAST SOUNDINGS SHOWED THE MOISTURE
WILL BE SHALLOW. EAST OF THE BLUE RIDGE WILL CLEAR OUT LATE
TONIGHT.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
AS OF 300 AM EDT SUNDAY...

AN UPPER LEVEL TROUGH WILL PIVOT ACROSS THE REGION WITH NORTHWEST
FLOW AND LOW LEVEL MOISTURE KEEPING CLOUDS BANKED UP AGAINST WESTERN
SLOPES THROUGH MONDAY MORNING. ONCE THIS TROUGH AXIS TRACKS TO THE
MID ATLANTIC COAST DURING THE AFTERNOON...DRY AIR WILL ERODE
MOUNTAIN CLOUDS WITH CLEAR CONDITIONS CONTINUING THROUGH THE REST OF
THE PERIOD. DOWNSLOPE FLOW IS EXPECTED EAST OF THE BLUE RIDGE TO
KEEP CLEAR SKIES THROUGH THE ENTIRE PERIOD.

FOLLOWING THE PASSING OF THE UPPER LEVEL TROUGH...A SURGE OF COOLER
DRIER AIR WILL MOVE OVER THE AREA. DEW POINTS WILL DROP INTO THE 40S
MONDAY AFTERNOON AND CONTINUE TO LOWER INTO THE 30S ACROSS THE
MOUNTAINS MONDAY NIGHT. OVERNIGHT LOWS WILL RANGE FROM THE UPPER 30S
IN MOUNTAIN VALLEYS TO THE UPPER 40S IN THE PIEDMONT. TEMPERATURES
WILL RUN 5F-10F COOLER THAN NORMAL MONDAY AND TUESDAY AFTERNOON.
ALSO MONDAY...PRESSURE RISES WILL BRING BREEZY AND GUSTY CONDITIONS
TO THE AREA...ESPECIALLY ALONG THE BLUE RIDGE. GUSTS ALONG THE BLUE
RIDGE COULD TOP OUT AT 30 MPH.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
AS OF 100 PM EDT SATURDAY...

THE EXTENDED PERIOD IS DOMINATED BY A 1032MB SURFACE HIGH THAT
STARTS IN SOUTHERN QUEBEC ON WEDNESDAY AND WILL SLOWLY DRIFT SOUTH
OVER THE NE STATES BY SATURDAY. THE RESULT OF THIS WILL BE AN
EASTERLY WEDGE FLOW THROUGH THE ENTIRE PERIOD. THERE IS SIGNIFICANT
DIFFERENCES IN PLACEMENT OF A MID LEVEL CLOSED LOW BY THE GFS AND
THE ECMWF TO OUR WEST...WHICH WILL IMPACT HOW MUCH MOISTURE CAN GET
PULLED INTO THE REGION. AT THIS POINT TRENDED TOWARD HPC AND THE
DRIER GFS SOLUTIONS AND KEPT JUST LOW CHANCE POPS ALONG AND EAST OF
THE BLUE RIDGE FROM THURSDAY THROUGH THE END OF THE PERIOD. ANY
PRECIP THAT DOES FALL WILL LIKELY BE JUST PATCHY DRIZZLE WITH LITTLE
TO NO ACCUMULATION.

WENT BELOW GUIDANCE FOR HIGH TEMPS AS THE MODELS ARE TYPICALLY TOO
WARM WITH AN EASTERLY FLOW. EXPECT SURFACE HIGHS OF MID TO UPPER 60S
ACROSS THE MOUNTAINS TO LOW 70S EAST OF THE BLUE RIDGE.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
AS OF 135 AM EDT SUNDAY...

HIGH CLOUDS AROUND A LOW OFF THE CAROLINA COAST WILL REDUCE FOG
DEVELOPMENT IN THE PIEDMONT OF VIRGINIA AND NORTH CAROLINA EARLY
THIS MORNING. DID NOT INCLUDE FOG AT KDAN AND KLYH FOR THIS
MORNING. SATELLITE PICTURES SHOWED A CLEAR SKY WEST OF THIS
CIRRUS. FOG WAS ALREADY FORMING AT KLWB IN THE GREENBRIER RIVER
VALLEY. LOW CONFIDENCE FOR HOW MUCH FOG WILL REDUCE THE VISIBILITY
AT KBCB THIS MORNING.

FOG WILL DISSIPATE AFTER DAYBREAK....BUT MOISTURE ADVANCING AHEAD
OF AN APPROACHING COLD FRONT WILL BRING MOSTLY CLOUDY SKIES...WITH
LOW END VFR CIGS BY LATE MORNING TO THE MOUNTAINS. SCATTERED
SHOWERS WILL ALSO DEVELOP IN THE MOUNTAINS DURING THE AFTERNOON.
LOW LEVEL WINDS INCREASE WITH THE APPROACHING FRONT...AND GUSTS
20-25KTS ARE POSSIBLE BY THIS AFTERNOON IN THE HIGHER ELEVATIONS.

WINDS BECOME WEST TO NORTHWEST BEHIND THE FRONT TONIGHT. MODELS
WERE SUGGESTING SOME LOW LEVEL MOISTURE WILL BANK UP AGAINST THE
WESTERN SLOPS OF THE APPALACHIANS LATE TONIGHT. MVFR CEILINGS ARE
POSSIBLE AT KBLF AND KLWB AFTER MIDNIGHT.

EXTENDED AVIATION DISCUSSION...

HIGH PRESSURE AND DRIER AIR IN THE REGION MONDAY THROUGH THURSDAY
WILL RESULT IN MAINLY VFR CONDITIONS. RIVER VALLEY FOG WILL STILL
BE POSSIBLE AT NIGHT.

&&

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

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS
SHORT TERM...RCS
LONG TERM...CF
AVIATION...AMS/PH


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