Area Forecast Discussion
Issued by NWS Blacksburg, VA

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FXUS61 KRNK 020539
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
139 AM EDT THU OCT 2 2014

.SYNOPSIS...
HIGH PRESSURE WILL AGAIN WEDGE SOUTH ALONG THE EASTERN SLOPES OF
THE APPALACHIANS THROUGH THURSDAY. A STRONG COLD FRONT ARRIVES
LATER FRIDAY FOLLOWED BY MUCH COOLER AIR FOR THE WEEKEND.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 100 AM EDT THURSDAY...

A FEW SHOWERS SHIFTING ACROSS BUCKINGHAM COUNTY EARLY THIS
MORNING...OTHERWISE DEALING WITH CLOUDS IN THE EAST WITH FOG
ELSEWHERE...MAINLY PATCHY AND DENSE IN RIVER VALLEYS AND OUT EAST.
MODELS FAVOR LOWER CLOUDS MOVING WWD TOWARD ROANOKE BEFORE DAWN
THEN ERODING LATE MORNING. MADE SOME ADJUSTMENTS TO SKY COVER TO
ACCOUNT FOR THIS...WITH LITTLE ADJUSTMENTS TO THE REST OF THE
FORECAST.

PREVIOUS DISCUSSION...


A WEAK DISTURBANCE PASSING ACROSS THE REGION THIS EVENING IS
TRIGGERING SPOTTY SHOWER ACTIVITY ACROSS AMHERST/APPOMATTOX/
BUCKINGHAM COUNTIES. FURTHER SOUTH HOWEVER...SKIES ARE MOSTLY
CLEAR AND...COMBINED WITH LIGHT WINDS AND DEWPOINT TEMPERATURES IN
THE LOW 60S...AM STARTING TO SEE REPORTS OF PATCHY FOG DEVELOPING
ACROSS THE SOUTHSIDE. HAVE UPDATED THE AFTERNOON FORECAST PACKAGE
TO ADD MENTION OF FOG AND TO EXTEND SHOWER ACTIVITY A LITTLE
LONGER INTO THE NIGHT. RAPID UPDATE MODELS INDICATE THAT NEARLY
ALL OF THE SHOWERS SHOULD BE OUT OF OUR AREA BY 2 AM.

LATER DURING THE NIGHT...WILL SEE 500 MB HEIGHT RISES AS OUR AREA
BECOMES SITUATED UNDER IN A WEAK RIDGE BETWEEN A DEPARTING UPPER
LOW WELL OFF THE EAST COAST AND THE DIGGING TROF OVER THE CENTRAL
UNITES STATES. WITH RIDGING TAKING SHAPE...WILL GO WITH
TEMPERATURES ABOVE GUIDANCE...WHICH HAS BEEN TOO COOL THE PAST FEW
NIGHTS. EXPECT LOW TEMPERATURES RANGING FROM THE LOW 50S/A FEW
UPPER 40S IN THE MOUNTAINS...TO THE UPPER 50S ACROSS THE PIEDMONT.

WEAK SURFACE COLD FRONT CROSSING INTO NORTH CAROLINA WILL
DISSIPATE BY THURSDAY MORNING...WITH HIGH PRESSURE OVER THE
FORECAST AREA DURING THE DAY. PREVAILING WIND FLOW WILL BE
WESTERLY...AND LOCATIONS THAT HAVE RAPID CLEARING OF FOG OR LOW
CLOUDS IN THE MORNING CAN EXPECT ABOVE NORMAL HIGH TEMPERATURES.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/...
AS OF 257 PM EDT WEDNESDAY...

A COLD FRONT WILL APPROACH THE REGION THURSDAY NIGHT. WITH AN
INCREASE IN MIXING AHEAD OF THIS FRONT...A SHALLOW WEDGE WILL
CONTINUE TO ERODE WITH A PIECE HANGING OVER THE PIEDMONT INTO
FRIDAY MORNING. AS EXPECTED...MODELS HAVE SLOWED DOWN THE TIMING
OF THE FRONT AND PREFRONTAL SHOWERS ENTERING THE AREA. THE FRONT
WILL ENTER THE OHIO VALLEY LATE IN THE MORNING WITH PREFRONTAL
SHOWERS TRACKING ACROSS EXTREME WESTERN PORTION OF THE COUNTY
WARNING AREA (SW VA/SE WV). BY EARLY AFTERNOON...THE FRONT MOVES
OVER THE OHIO VALLEY AND SHOWERS ADVANCE EAST TO THE BLUE RIDGE.
THE FRONT CROSSES OVER THE MOUNTAINS DURING THE EVENING WITH
SHOWERS OVER THE FOOTHILL AND PIEDMONT COUNTIES...EXITING DURING
THE EARLY MORNING HOURS SATURDAY. PRECIPITATION TIMING MAY VARY BY
A COUPLE OF HOURS...AS THE CLOSED LOW CYCLES AND REORGANIZES OVER
THE UPPER MISSISSIPPI FRIDAY.

AS THE FRONT TRACKS TO THE EAST COAST SATURDAY MORNING...THE
CLOSED LOW WILL MOVE EAST INTO THE OHIO VALLEY. A SHORT WAVE WITH
THIS LOW LOOKS TO TRACK FARTHER TO THE SOUTH AND OVER THE
TENNESSEE VALLEY. WITH THIS TRACK...THICK CLOUDS WILL REMAIN OVER
THE MOUNTAINS...ESPECIALLY ALONG WESTERN SLOPES THROUGH SATURDAY
MORNING. AS THIS SHORT WAVE EXITS THE FORECAST AREA...WEST WINDS
WILL INCREASE AND CLOUDS WILL EVENTUALLY DISSIPATE. UNTIL THE
CLOUDS ARE GONE...BREEZY/GUSTS WINDS SHOULD REMAIN ALONG HIGHER
RIDGES THEN MIX DOWN SATURDAY AFTERNOON. HIGH PRESSURE TRACKING
ALONG THE GULF STATES WILL STRETCH NORTH SATURDAY NIGHT ALLOWING
WINDS TO SUBSIDE.

WITH THE SLOWER ARRIVAL OF SHOWERS ON FRIDAY...WARMED
TEMPERATURES A FEW DEGREES WITH L/M 70S WEST AND U70S/L80S EAST.
ALONG WITH WARMER TEMPERATURES...INSTABILITIES WILL
INCREASE...THEREFORE INCREASE THUNDERSTORMS ACTIVITY FROM ISOLATED
TO SCATTERED FRIDAY AFTERNOON/EVENING. A DRAMATIC CHANGE IN
TEMPERATURES AND HUMIDITY WILL BE FELT SATURDAY AS TEMPERATURES
WILL RUN 5F-10F COOLER THAN NORMAL.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
AS OF 310 PM EDT WEDNESDAY...

FOLLOWING THE PASSING OF A COLD FRONT FRIDAY NIGHT...THE REGION
WILL REMAIN UNDER AN UPPER LEVEL TROUGH THROUGH EARLY NEXT WEEK.
COOLER THAN NORMAL AFTERNOON TEMPERATURES LIKELY THROUGH
MONDAY...THEN MODERATING TOWARDS NORMAL BY MID WEEK. OVERNIGHT
LOWS SATURDAY AND POSSIBLY SUNDAY NIGHT WILL BE COLD WITH
MOUNTAINS TEMPERATURES DROPPING INTO THE 30S...40S IN THE EAST.
FROST IS POSSIBLE ACROSS THE WEST IF WINDS COULD DECOUPLE EARLY
SUNDAY MORNING. GROUND TEMPERATURES WILL REMAIN WARM ENOUGH TO
LIMIT ANY FROST TO ISOLATED AREAS.

THE EASTERN HALF OF THE USA WILL REMAIN UNDER A BROAD BUT FLAT
TROUGH THROUGH TUESDAY. THERE COULD BE A MID LEVEL DISTURBANCE
MOVING ACROSS THE OHIO VALLEY MONDAY...BUT WITH LIMITED
MOISTURE...JUST SEEING AN INCREASE IN CLOUD COVER FOR THE AREA.
TUESDAY MAYBE THE NEXT CHANCE FOR RAIN...AS A FRONT IS SCHEDULED
TO MOVE OVER THE REGION.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 130 AM EDT THURSDAY...

ANOTHER VARIABLE NIGHT OUT EAST FOR TAFS...WITH MVFR CIGS AT LYH
TO IFR/LIFR VSBYS AT DAN. MODELS FAVOR VSBYS DROPPING DESPITE THE
LOWER CLOUDS AT LYH...AND HAVE THIS IN BY 09Z. TO THE WEST...THINK
MVFR CIGS COULD SHIFT INTO ROANOKE BY 09Z AS WELL BUT WILL BE A
SCT V BKN SITUATION BUT LEANED TOWARD BKN..WITH MVFR FOG.

BLF WILL STAY VFR WHILE LWB/BCB SEE CLEAR SKIES BUT FOG REDUCING
VSBYS DOWN TO 1/4SM.

FOG BURNS OFF IN THE WEST BY 14Z...WHILE THE SUB VFR CIGS IN THE
EAST HANG TOUGH THROUGH ABOUT MIDDAY BEFORE SCATTERING OUT.

WIND FIELDS REMAIN LIGHT THROUGH THE PERIOD.

EXTENDED AVIATION DISCUSSION...

FRONTAL BOUNDARY AND ASSOCIATED SHOWERS TO IMPACT THE MOUNTAINS BY
LATE FRIDAY MORNING AND THE PIEDMONT IN THE AFTERNOON. SUB VFR
EXPECTED IN HEAVIER SHOWERS OR ISOLATED TSRA.

SHOWERS EXITING THE MTNS BY LATE FRIDAY EVENING AND THE PIEDMONT
TOWARD DAWN SATURDAY. TIMING OF CLEARING IS STILL TRICKY.
SATURDAY SHOULD BE CLEARING OUT IN THE PIEDMONT TO
ROANOKE/BLACKSBURG BUT UPSLOPE MVFR CIGS AT BLF/LWB MAY OCCUR INTO
SAT AFTERNOON...WITH BREEZY NW WINDS.

WINDS DIMINISH SATURDAY NIGHT THEN VFR SUNDAY INTO MONDAY. A FRONT
CLOSES IN MONDAY AFTERNOON WITH SOUTHWEST WINDS INCREASING. LOOKS
LIKE SHOWERS MAY IMPACT THE MOUNTAINS BY MONDAY EVENING...WITH
POSSIBLE SUB VFR.

&&

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

&&

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


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