Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 210640
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
240 AM EDT THU AUG 21 2014

.SYNOPSIS...
A WEAK STATIONARY FRONT WILL REMAIN IN THE AREA THROUGH THE REST
OF THE WEEK. UPPER LEVEL DISTURBANCES TRACKING EAST AND SOUTHEAST
ACROSS THE BOUNDARY WILL BRING SCATTERED SHOWERS AND STORMS TO THE
REGION EACH DAY. THE FRONT SHOULD SHIFT BACK SOUTH OF THE REGION
SATURDAY BRINGING A RETURN TO COOLER WEATHER FOR THE WEEKEND.

&&

.NEAR TERM /THROUGH TODAY/...
AS OF 1120 PM EDT WEDNESDAY...

MLCAPES OVER 1500 J/KG STILL LINGERING OVER THE PIEDMONT LATE THIS
EVENING KEEPING CONVECTION ONGOING FROM THE NC/VA LINE NORTH INTO
BUCKINGHAM COUNTY. AIRMASS HAS BEEN WORKED OVER ACROSS THE
MTNS...AND DESPITE A STRONGER WAVE DEPICTED BY LATEST RAP ANALYSIS
OVER KY...NOT SEEING MUCH OF ANYTHING EXCEPT ISOLATED/WIDELY
SCATTERED SHOWER THREAT THROUGH 3 AM OUT OVER FAR SW VA INTO NW
NC. THINK THE CONVECTION OUT EAST WILL EXIT THE CWA BY 1 AM.

SKIES WILL BE VARIABLY CLOUDY WITH LOTS OF HIGH CLOUDINESS ACROSS
THE WEST AND SOUTH. CLEARING TAKES PLACE INTO EARLY MORNING OUT
EAST...WITH MORE CLOUDS ARRIVING INTO THE APPALACHIANS AHEAD OF
THE NEXT SHORTWAVE MOVING OVER ILLINOIS THIS EVENING. MODELS HAVE
SLOWED TIMING DOWN SOME WITH ONSET OF NEXT ROUND OF SHOWERS IN THE
MTNS...SO DELAYED CHANCES A COUPLE OF HOURS.

FOG MAY BE MORE OF AN ISSUE OUT EAST IF/WHEN IT CLEARS ESPECIALLY
WHERE IT RAINED. FOR NOW KEPT IN PATCHY FOG...WITH AREAS CLOSER TO
BUCKINGHAM COUNTY. LOW TEMPS REMAIN MUGGY IN THE 60S.




WEAK RESIDUAL FRONT WILL LIFT BACK NE ON THURSDAY AS THE WAVE CHANNEL
ALOFT AROUND THE RIDGE TO THE SW AMPLIFIES A BIT AND STARTS TO SHIFT
NORTH AS WELL. MODELS BRING ANOTHER IMPULSE QUICKLY SE OUT OF THE
UPSTREAM CONVEYER BELT AND DRIVE IT TOWARD THE NW COUNTIES
THURSDAY MORNING SIMILAR TO TODAY...PERHAPS JUST A BIT SLOWER.
HOWEVER LIFT WILL BE ENCOUNTERING DEEP NW FLOW SO UNCERTAIN AS TO
HOW FAR THIS COMPLEX MAY GET BEFORE FADING. THUS RUNNING WITH
INCREASING CHANCE POPS THURSDAY MORNING...MAINLY BLUE RIDGE
WEST...WITH HIGHEST ACROSS SE WEST VA. EXPECT EARLY CONVECTION TO
AGAIN FADE CROSSING THE RIDGES AS WE SLIP IN BETWEEN WAVES BEFORE
BETTER INSTABILITY/OUTFLOW HELPS REDEVELOP AT LEAST SCATTERED
AFTERNOON COVERAGE MOUNTAINS...AND ISOLATED OUT EAST WHERE
DOWNSLOPE ALOFT WILL BE STRONGER. THEREFORE TRIMMED BACK POPS TO
MORE CHANCE NATURE GIVEN TRENDS OF LATE AND LACK OF MUCH LIFT
THURSDAY AFTERNOON WITH THE NEXT WAVE IN OHIO. WARMING ALOFT AND
WESTERLY WINDS SHOULD COMBINE WITH SUNSHINE TO PUSH TEMPS ABOVE 90
SE WITH 80S MOST OTHER SPOTS PENDING EARLY CLOUDS.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
AS OF 245 PM EDT WEDNESDAY...

FORECAST AREA STAYS IN BROAD NORTHWEST SYNOPTIC FLOW. PROBABILITY
OF PRECIPITATION WILL DEPEND ON WHEN SHORT WAVES COME THROUGH.
SHOWERS AND THUNDERSTORMS THAT CROSS THE COUNTY WARNING AREA
DURING THE LATE NIGHT OR EARLY MORNING...OR UPSTREAM CLUSTERS OF
STORMS THAT SPREAD CLOUDS DOWNSTREAM OVER US WILL DIMINISH THE
AVAILABLE INSTABILITY.

MODELS HAVE AXIS OF BEST LIFT SHIFTING JUST NORTH OF THE FORECAST
AREA ON FRIDAY. THIS MAY LIMIT THE COVERAGE OF PRECIPITATION FOR
FRIDAY THROUGH SATURDAY. BUT SURFACE BOUNDARY POSSIBLY MOVING SOUTH
THROUGH THE EASTERN PART OF THE FORECAST AREA ON FRIDAY MAY TRIGGER
SHOWERS AND THUNDERSTORMS. PRECIPITABLE WATER VALUES REMAIN HIGH
THROUGH THE PERIOD. LARGE RAINFALL RATES WILL BE POSSIBLE IN ANY OF
THE STORMS.

EXPECTING MUGGY CONDITIONS OVERNIGHT WITH DEW POINTS REMAINING WELL
INTO THE 60S. 850 TEMPERATURES ON THE EASTERN SIDE OF THE FORECAST
AREA WILL BE COOLER THAN IN THE WEST. OVERALL PRECIPITATION AND
CLOUD COVER WILL HOLD TEMPERATURES AT OR JUST BELOW NORMAL FOR
MAXIMUM TEMPERATURES.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AS OF 300 PM EDT WEDNESDAY...

LARGE UPPER RIDGE BUILDS FROM THE LOWER MISSISSIPPI VALLEY. 500 MB
HEIGHTS OVER THE FORECAST AREA BEGIN TO RISE ON TUESDAY WITH THE
RIDGE CENTERED OVER THE TENNESSEE VALLEY.

SURFACE HIGH PRESSURE WILL BE OVER NEW ENGLAND AND WEDGED DOWN THE
APPALACHIANS THROUGH TUESDAY. BY THURSDAY A STRONG BERMUDA HIGH WILL
BE IN PLACE.

CHALLENGING TO TIME SHORT WAVES COMING OVER THE TOP OF THE RIDGE.
WPC WAS FAVORING A BLEND OF ENSEMBLE GFS AND ECMWF THROUGH THE
PERIOD. THIS KEEPS FORECAST AREA IN A PERSISTENT CHANCE OF
PRECIPITATION THROUGH MONDAY NIGHT. AT THIS TIME WILL BE
EMPHASIZING SUNDAY NIGHT AS THE BEST CHANCE IN THIS TIME FRAME.

WILL BE WARMING UP CLOSER TO ABOVE NORMAL TEMPERATURES ASSOCIATED
WITH THE UPPER RIDGE ON WEDNESDAY.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
AS OF 230 AM EDT THURSDAY...

PATCHY MORNING FOG ANTICIPATED AREAWIDE...MAINLY MVFR...BUT CAN`T
RULE OUT BRIEF PERIOD OF IFR/LIFR FOR A FEW HOURS AROUND DAYBREAK.
ANY FOG AND STRATUS THAT FORMS WILL DISSIPATE AFTER SUNRISE WITH
WIDESPREAD VFR CONDITIONS DEVELOPING AFTER 13Z/9AM.

SHALLOW EASTERLY SURFACE WINDS THIS MORNING WILL GIVE WAY TO WEST
NORTHWEST WINDS LATER THIS MORNING. THE LOW LEVEL FLOW WILL BE
FROM THE NORTHWEST TODAY...WINDS 6-12 KTS...AND GUSTY NEAR THE
RIDGE CRESTS. THE DEEPER FLOW...WELL ALOFT...IS ALSO FROM THE
NORTHWEST. THIS WILL TRANSPORT DEBRIS CLOUDINESS DOWNSTREAM FROM
THUNDERSTORMS OVER THE MIDWEST AND OHIO VALLEY REGIONS...CLOUD
LAYERS MAINLY ABOVE 10KFT.

WITH WINDS OUT OF THE WEST TODAY...THIS WILL CREATE DOWNSLOPE
COMPRESSIONAL WARMING AND SUBSIDENCE. DO NOT EXPECT MUCH IN THE
WAY OF LOCAL STORM ACTIVITY...DEEP CONVECTION...DUE TO THIS
DOWNWARD VERTICAL MOTION. THE SUBSIDENCE IS EXPECTED TO WEAKEN
TOWARD SUNSET...THUS POTENTIAL FOR STORM ACTIVITY WILL
INCREASE...BUT MAINLY CONFINED LATER IN THE TAF PERIOD.

THUNDERSTORMS ARE EXPECTED TO DEVELOP TODAY VCNTY OF STALLED
FRONTAL BOUNDARY OVER THE OHIO VALLEY. STORMS WHICH DEVELOP VCNTY
OF THIS BOUNDARY...ACROSS IL/IN/OH/KY...WILL MOVE DOWNSTREAM
TOWARD THE MID ATLANTIC REGION THIS EVENING AND DURING THE
OVERNIGHT TONIGHT.

HIGHEST CONFIDENCE FOR STORMS THIS AFTERNOON WILL BE FROM WEST
VIRGINIA INTO THE OHIO VALLEY...THE THREAT TRANSITIONING
DOWNSTREAM INTO VIRGINIA AND NORTH CAROLINA TONIGHT. INTRODUCED
VCNTY TSRA FOR ALL THE TERMINALS AFTER 22Z/6PM...THE STORM THREAT
PERSISTING THROUGH THE OVERNIGHT. CONFIDENCE IS HIGHER FOR THE WV
TERMINALS.

EXTENDED AVIATION...

UPPER LEVEL DISTURBANCES WILL BE MOVING THROUGH PERIODICALLY AND
INTERACTING WITH A STATIONARY FRONT OVER THE AREA FOR THE NEXT FEW
DAYS...RESULTING IN PERIODS OF SHOWERS AND THUNDERSTORMS. DUE TO
THE HIGH MOISTURE CONTENT OF THE AIR...EXPECT STRATUS AND FOG
DURING THE OVERNIGHT PERIODS WITH AREAS OF MVFR/IFR MOST
PRONOUNCED BETWEEN MIDNIGHT AND 9AM EACH DAY. MODELS ARE INDICATED
THAT A DEEPER EASTERLY SORT OF WIND FLOW WILL SETUP FOR THIS
UPCOMING WEEKEND. THIS SUGGEST THAT LOW CIGS MAY PERSIST EVEN
DURING THE DAYTIME PERIODS...SATURDAY AND SUNDAY...WITH WIDESPREAD
MVFR CONDITIONS ACROSS THE AREA THIS WEEKEND DUE TO MOISTURE
BANKING UP AGAINST THE EAST SIDE OF THE APPALACHIANS.

&&

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

&&

$$
SYNOPSIS...JH
NEAR TERM...JH/WP
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...PM



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