Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 291808
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
208 PM EDT FRI AUG 29 2014

.SYNOPSIS...
A WEAK FRONT WILL BE STATIONARY FROM NORTH CAROLINA TO MISSOURI
TODAY. THIS FRONT WILL LIFT NORTH INTO THE OHIO VALLEY TONIGHT. A
STRONGER SYSTEM WILL BRING A BETTER THREAT FOR SHOWERS AND STORMS
FOR SUNDAY AND MONDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 1247 PM EDT FRIDAY...

LATEST LAPS DATA ARE SHOWING SURFACE BASED LI OF -2 TO -3 AND CAPS
AROUND 500 J/KG ACROSS TAZEWELL AND SMYTH COUNTIES. HIGHER VALUES
EXIST WEST OF THE FORECAST AREA IN SOUTHERN WEST VIRGINIA AND
NORTHEAST TENNESSEE. NO SHOWERS DETECTED YET ON REGIONAL RADARS IN
THAT REGION...BUT VISIBLE SATELLITE IMAGERY IS STARTING TO SHOW
THE DEVELOPMENT OF CUMULUS CLOUDS...SO AM NOT EXPECTING TOO LONG
OF WAIT FOR THE FIRST SHOWERS TO DEVELOP. LATEST HRRR AND RNK WRF-
ARW ARE ON TARGET FOR ABOUT A 18-19Z/2PM-3PM INITIATION TIME.

THE OTHER AREA OF THE REGION THAT WE HAVE BEEN WATCHING FOR
DEVELOPMENT IS SOUTHSIDE VIRGINIA AND NEIGHBORING NORTH CENTRAL
NORTH CAROLINA. THIS REGION HAS HAD DECENT CLOUD COVER OVER IT FOR
THE MORNING...AND NOW THE EARLY AFTERNOON. LAPS...AS
EXPECTED...STILL HAS THE AREA STABLE. FOR OUR FORECAST...HAVE
DELAYED THE ONSET OF ANY ISOLATED SHOWER OR THUNDERSTORM ACTIVITY
UNTIL LATER IN THE AFTERNOON...PERHAPS STARTING AROUND OR AFTER
21Z/5PM. HAVE ALSO LOWERED EXPECTED HIGH TEMPERATURES IN THIS AREA
BY A COUPLE OF DEGREES THANKS TO THE CLOUDS. HAVE RAISE FORECAST
HIGHS IN THE FAR WESTERN PARTS OF THE ARE BASED UPON CURRENT
TEMPERATURES AND CONTINUED WARMING TREND THROUGH THE AFTERNOON.

AS OF 947 AM EDT FRIDAY...

LATEST MESOSCALE MODELS STILL OFFERING BEST CHANCE FOR CONVECTION
TODAY TO BE ACROSS THE WESTERN QUARTER OF THE REGION. LATEST LAPS
DATA SHOW SURFACE BASED LI VALUES HAVE JUST DROPPED BELOW ZERO AND
A FEW HUNDRED SURFACE BASED CAPE HAVE DEVELOPED IN WESTERN
TAZEWELL AND SMYTH COUNTIES. THIS AREA AND THE SURROUNDING AREA IS
EXPECTED TO BECOME MORE UNSTABLE WITH THE HEATING OF THE
AFTERNOON. INITIAL CONVECTION TIME IS EXPECTED TO BE SOMEWHERE
BETWEEN 17Z-18Z/1PM-2PM IN THIS REGION AND MAINTAIN THROUGH THE
AFTERNOON. ANOTHER AREA WE ARE STILL WATCHING IS SOUTHSIDE
VIRGINIA AND NEIGHBORING PORTIONS OF NORTH CENTRAL NORTH
CAROLINA. WHILE STILL STABLE AT THE SURFACE...THIS AREA IS
EXPECTED TO BECOME UNSTABLE THIS AFTERNOON IN PROXIMITY TO THE
STALLED FRONTAL BOUNDARY. NO MAJOR CHANGES TO THE FORECAST.

AS OF 400 AM EDT FRIDAY...

STATIONARY FRONT TRAILED FROM NORTHEAST NORTH CAROLINA TO NORTH
CENTRAL TENNESSEE EARLY THIS MORNING.

ALONG THE BOUNDARY AND WEST OF THE BLUE RIDGE MODELS WERE SHOWING
A CHANCE OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING.
WILL BE STARTING OFF THE DAY CAPPED. EVEN IF THE CAP DOES
BREAK...AS SUGGESTED BY BUFKIT NAM/RAP GUIDANCE...NOT MUCH
INSTABILITY...AND NOT UNTIL AFTER 18Z. WITH THE SHORT WAVE ENERGY
WELL WEST AND NORTH OF THE FORECAST AREA...LITTLE TO AIDE IN THE
FORCING TODAY.

AXIS OF POOLED MOISTURE AND LOW LEVEL CONVERGENCE ALONG THE WEAK
BOUNDARY PIVOTS NORTHEAST TONIGHT AND WILL EXTEND FROM OHIO INTO
EASTERN NORTH CAROLINA BY SATURDAY MORNING.

WILL HAVE BEST PROBABILITY OF SHOWERS AND THUNDERSTORMS IN THE
EXTREME SOUTHWEST COUNTY WARNING AREA. AREAL COVERAGE OF
PRECIPITATION SHOULD ONLY BE ISOLATED TO SCATTERED. STORM MOTION
WOULD BRING THE STORMS INTO SOUTHEAST WEST VIRGINIA AND POSSIBLY THE
NEW RIVER VALLEY AROUND 00Z. BUT NOT MUCH INSTABILITY LEFT BY THAT
TIME.

SOUTHEAST WINDS AT THE SURFACE THROUGH LOW LEVELS...BRING 850-1000MB
RELATIVE HUMIDITY UP TODAY AND BY TONIGHT LOW CLOUDS ARE EXPECTED TO
ADVANCE TOWARD THE EAST SIDE OF THE APPALACHIANS.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
AS OF 310 AM EDT FRIDAY...

UPPER RIDGE EXPECTED TO SHIFT EAST AS STRONGER UPPER TROUGH MOVES
FROM THE UPPER MIDWEST INTO THE GREAT LAKES. MODELS AGREE THAT A
SOUTHERN STREAM UPPER SHORTWAVE WITH ENHANCEMENT IN THE JET WILL
STREAK OVER THE GULF COAST STATES AND ACROSS THE WESTERN SLOPES OF
THE APPALACHIANS SUNDAY. FOR SATURDAY THOUGH...MAINLY LOOKING WEAK
FLOW ALOFT WITH SOME CONVERGENCE ACROSS THE MTNS PER SOUTH-SOUTHEAST
FLOW. MODELS ARE FAVORING A BIT OF CONVECTION WITH THE LEE TROUGH IN
THE EAST...MAINLY FROM THE EASTERN WV PANHANDLE SOUTHEAST TOWARD THE
TIDEWATER. THINK THE AIRMASS WILL BE UNSTABLE AND MOIST ENOUGH TO
TRIGGER A FEW STORMS BUT OVERALL UPPER SUPPORT IS LACKING SO ONLY
SEEING ISOLATED COVERAGE OVER THE MTNS AND NORTH OF A ROANOKE TO
DANVILLE LINE. MORE SUN SATURDAY WILL BRING TEMPS TOWARD 90 OUT EAST
WITH MID 80S WEST.

SAT NIGHT...MAIN AXIS OF CONVECTION WILL RUN FROM MS-KY...WITH
LITTLE TO NO CHANCE OF SHOWERS EAST OF THE BLUE RIDGE AFTER EVENING
STORMS WANE. WITH THE UPPER SUPPORT TRACKING CLOSER WILL HAVE AT
LEAST SLIGHT CHANCE INTO THE MOUNTAINS LATE.

SUNDAY LOOKS ACTIVE AS THE SHORTWAVE AXIS SHIFTS ACROSS KY INTO
NORTHERN WV...WITH STRONG CONVERGENCE AND LIFT. WILL SEE HIGH
CHANCE/LIKELY POPS. LOOKS LIKE CLOUD COVER COULD ARRIVE SOON ENOUGH
TO KEEP INSTABILITY LOWER...BUT ENOUGH UPPER SUPPORT/SHEAR WHERE A
FEW STORMS COULD PRODUCE GUSTY WINDS. THE SHORT WAVE AXIS SLOWLY
SHIFTS TO THE EAST AND WITH A LEE TROUGH...CONVECTION FIRES LATE IN
THE AFTERNOON AND MAY REMAIN OVER SOUTHSIDE UNTIL MIDNIGHT. HIGHS
SUNDAY WILL RANGE FROM THE UPPER 70S MOUNTAINS TO UPPER 80S TOWARDS
SOUTHSIDE.

OVERALL...LABOR DAY WEEKEND LOOKING VERY WARM/HOT/HUMID. SATURDAY
NOT TOO BAD RAIN WISE...BUT STAY COOL WHILE DRINKING PLENTY OF WATER
IF OUTDOORS. SUNDAY APPEARS POOR FOR OUTDOOR ACTIVITIES.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
AS OF 300 PM EDT THURSDAY...

MUCH OF THE LONG TERM PERIOD WILL BE INFLUENCED BY A MEAN UPPER
RIDGE THAT WILL INITIALLY RESIDE ALONG AND OFF THE SOUTHEAST
COAST...WHICH GRADUALLY RETROGRESSES AND EXPANDS WESTWARD INTO THE
GULF COAST STATES BY THE END OF THE FORECAST PERIOD.

SOUTHEASTERN RIDGE WILL INITIALLY BE STRONG ENOUGH TO DEFLECT ANY
NORTHERN STREAM ENERGY AWAY FROM THE BLACKSBURG FORECAST AREA...WITH
MAIN BAROCLINIC ZONE REMAINING FROM THE NORTHERN PLAINS EAST INTO
AND THROUGH THE GREAT LAKES INTO NEW ENGLAND.

HOWEVER...TAP OF TROPICAL MOISTURE RIDING AROUND PERIPHERY OF
SOUTHEASTERN RIDGE LIKELY TO REMAIN OVER/NEAR THE BLACKSBURG
FORECAST AREA THROUGH AT LEAST MONDAY OR MONDAY NIGHT...MAINTAINING
THREAT FOR MAINLY DIURNALLY DRIVEN SCATTERED SHOWERS AND
THUNDERSTORMS...SOME OF WHICH MAY BE ACCOMPANIED BY LOCALLY HEAVY
RAIN CONSIDERING RELATIVELY HIGH PRECIPITABLE WATER VALUES EXPECTED
OVER THE AREA.

GRADUAL RETROGRESSION OF UPPER RIDGE INTO NORTHERN GULF COAST REGION
DURING THE MIDWEEK PERIOD SHOULD BE SUFFICIENT TO ALLOW WINDS ALOFT
TO VEER SUCH THAT INFLUENCE OF TROPICAL MOISTURE TAP GRADUALLY
WANES...ONLY TO BE REPLACED BY MORE AGGRESSIVE SOUTHWARD INTRUSION
OF NORTHERN STREAM ENERGY AND ASSOCIATED SCATTERED SHOWERS/STORMS IN
ADVANCE OF AN ACCOMPANYING DECAYING COOL FRONT INTO THE MID
APPALACHIAN AND MID ATLANTIC REGION IN TUESDAY-WEDNESDAY TIMEFRAME.

PUSH OF POST-FRONTAL SLIGHTLY DRIER AIR MAY BE STRONG ENOUGH TO
REDUCE THREAT FOR PRECIPITATION ACROSS AREAS NORTH OF INTERSTATE 64
BY THURSDAY...BUT WITH AT LEAST A CHANCE THREAT FOR SHOWERS/STORMS
REDEVELOPING BY AFTERNOON ACROSS THE SOUTHWESTERN MOUNTAINS CLOSER
TO DECAYING FRONTAL BOUNDARY AND PROXIMITY TO HIGHER THETA-E AIR.

PLENTY OF CLOUD COVER AND DEWPOINTS PRIMARILY IN THE 60S SHOULD
ENSURE THAT TEMPERATURES REMAIN CLOSE TO SEASONAL AVERAGES...MAINLY
MID 70S TO LOWER 80S ACROSS THE HIGHER ELEVATIONS BY DAY WITH UPPER
80S ACROSS THE PIEDMONT...WITH MAINLY 60S AT NIGHT. INTRUSION OF
SLIGHTLY COOLER/DRIER POST-FRONTAL AIR FROM THE NORTHEAST MAY ALLOW
TEMPERATURES TO BE A FEW DEGREES COOLER ON THURSDAY.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
AS OF 130 PM EDT FRIDAY...

VISIBILITY SENSOR AT KDAN REMAINS INOPERABLE. PARTS ARE ON
ORDER. UNTIL REPAIRS COMPLETE...NO ADMENDMENTS WILL BE SCHEDULED.

MORNING MVFR STRATOCU CLOUDS OVER MUCH OF THE CENTRAL AND
SOUTHEASTERN PARTS OF THE REGION HAVE FINALLY ERODED...OR LIFTED
TO LOW END VFR SCT-BKN. THE ATMOSPHERE IS BECOMING UNSTABLE ACROSS
THE WESTERN PART OF THE REGION BETWEEN KBLF-KTNB. NEW MVFR-LOW END
VFR CUMULUS CLOUDS ARE DEVELOPING IN THIS REGION...AND ISOLATED
SHOWERS AND PERHAPS A FEW THUNDERSTORMS ARE EXPECTED THIS
AFTERNOON INTO THE EARLY EVENING IN THIS REGION.

OVERNIGHT...A STATIONARY FRONT WILL MAKE SOME PROGRESS NORTH AS A
WARM FRONT ALONG WITH SOME PATCHY SHOWERS SOUTH OF IT. LOW LEVEL
MOISTURE WILL INCREASE AN BECOME TRAPPED UNDER THE NOCTURNAL
INVERSION. ANTICIPATE MOST OF THE REGION TO DEVELOP MVFR CIGS WITH
SOME REGIONS OF IFR. VSBYS WILL ALSO DECREASE WITH MOST AREAS
HAVING MVFR WITH POCKETS OF IFR.

ANY SUB-VFR CONDITIONS WILL BE FAIRLY SLOW TO IMPROVE TO VFR AFTER
SUNRISE SATURDAY. 15Z/11AM IS THE MOST LIKELY TIME MOST OF THE
REGION WILL BE BACK TO VFR.

EXTENDED DISCUSSION...

ANY ISOLATED OR SCATTERED SHOWERS AND STORMS WILL BE MAINLY
CONFINED TO AN AREA ALONG AND NORTH OF A KHSP-KFVX LINE SATURDAY
AFTERNOON...JUST SOUTH OF THE AGAIN STALLED FRONTAL BOUNDARY.

LATE SATURDAY NIGHT THROUGH SUNDAY EVENING AN AREA OF LOW PRESSURE
WILL HEAD EASTWARD THROUGH THE GREAT LAKES REGION TOWARD NEW
ENGLAND. ITS ASSOCIATED COLD FRONT WILL SWEEP THROUGH THE REGION
BRINGING A GENEROUS COVERAGE OF SHOWERS AND SOME STORMS. SUB-VFR
CONDITIONS ARE EXPECTED TO ACCOMPANY THE SYSTEM AND PRECIPITATION.

ANOTHER COLD FRONT IS EXPECTED TO PRODUCE SIMILAR CIRCUMSTANCES
TUESDAY INTO TUESDAY NIGHT. HOWEVER...MODEL GUIDANCE FOR THIS ONE
OFFERS PRECIPITATION IN A MORE SCATTERED DISTRIBUTION. AS
SUCH...THE MAGNITUDE OF SUB-VFR CONDITIONS MAY BE LESS.

&&

.EQUIPMENT...
AS OF 730 AM EDT FRIDAY ...

THE VISIBILITY SENSOR AT KDAN...DANVILLE REGIONAL AIRPORT...WILL
BE OUT OF SERVICE UNTIL FURTHER NOTICE. A PART HAS BEEN BACK-ORDERED.

&&

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

&&

$$
SYNOPSIS...AMS
NEAR TERM...AMS/DS
SHORT TERM...RCS
LONG TERM...WERT
AVIATION...DS
EQUIPMENT...AMS


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