Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000
FXUS61 KRNK 222008
AFDRNK

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BLACKSBURG VA
408 PM EDT FRI AUG 22 2014

.SYNOPSIS...
A STRONG UPPER LEVEL RIDGE OF HIGH PRESSURE IS CENTERED OVER THE
LOWER MISSISSIPPI RIVER VALLEY WITH A STATIONARY SURFACE FRONT
EXTENDING FROM THE UPPER MIDWEST...THROUGH THE OHIO VALLEY AND
INTO THE MID ATLANTIC STATES. THIS FRONT WILL BE THE FOCUS FOR
PERIODIC ROUNDS OF SHOWERS AND STORMS FROM THE OHIO VALLEY INTO
THE MID ATLANTIC THIS EVENING AND TONIGHT. OVER THE WEEKEND THE
FRONT IS EXPECTED TO MOVE SOUTH ALONG THE EAST COAST...TURNING
INTO A BACKDOOR COLD FRONT WHICH WILL BRING COOLER AIR TO AREAS
EAST OF THE APPALACHIANS...WHILE VERY WARM SULTRY WEATHER
CONTINUES ACROSS THE MID SECTION OF THE UNITED STATES.

&&

.NEAR TERM /THROUGH SATURDAY/...
AS OF 400 PM EDT FRIDAY...

SHOWERS AND THUNDERSTORMS CONTINUE TO DEVELOP OVER SOUTHERN WEST
VIRGINIA THIS AFTERNOON...WITH STRONG DAYTIME HEATING ALLOWING
THE STORM TO INTENSIFY AS THEY DRIFT SOUTHEAST TOWARD OUR
SOUTHEAST WEST VIRGINIA AND MOUNTAIN EMPIRE COUNTIES. THE MAIN
CONCERN FOR THIS EVENING WILL BE HEAVY RAIN. VERY MOIST
ATMOSPHERIC CONDITIONS ARE IN PLACE...AS EVIDENCED BY DEWPOINT
TEMPERATURES IN THE MID 70S AND PRECIPITABLE WATER VALUES IN
EXCESS OF 2 INCHES. AS SUCH...SHOWERS AND THUNDERSTORMS PASSING
ACROSS OUR AREA WILL BE VERY EFFICIENT RAINFALL PRODUCERS...
CAPABLE OF 2 TO 3 INCH PER HOUR RAINFALL RATES. SOILS ACROSS THE
MOUNTAINS ARE PRETTY CLOSE TO SATURATION FROM RECENT RAINFALL...SO
WILL BE KEEPING AN EYE OUT THIS EVENING FOR AREAS OF EXCESSIVE
RAINFALL...ESPECIALLY WHERE SHOWERS/STORMS PASS REPEATEDLY OVER
THE SAME LOCATIONS.

OVERNIGHT...RAINFALL WILL DIMINISH IN COVERAGE WITH THE LOSS OF
DAYTIME HEATING...BUT WILL STILL SEE SHOWERS PASS ACROSS OUR AREA.
WARM AND MUGGY CONDITIONS WILL PERSIST...HOWEVER A BACKDOOR COLD
FRONT WILL BEGIN TO DROP SOUTH ACROSS OUR AREA AS HIGH PRESSURE
BUILDS IN FROM THE GREAT LAKES REGION. REGARDLESS...LIGHT WINDS...
MOIST SOILS AND BREAKS IN THE CLOUD COVER WILL ALLOW PATCHY DENSE
FOG TO DEVELOP ONCE AGAIN. OVERNIGHT LOWS WILL RANGE FROM THE MID
60S WEST TO AROUND 70 EAST.

THE COLD FRONT WILL CONTINUE TO PUSH SOUTH ON SATURDAY. WILL SEE
NORTHEASTERLY WINDFLOW ACROSS THE PIEDMONT AS HIGH PRESSURE
CONTINUES TO WEDGE SOUTH...WHILE NORTHWESTERLY WINDS WILL PERSIST
ACROSS THE MOUNTAINS. AS SUCH...SHOULD SEE A REDEVELOPMENT OF
SHOWERS ALONG THE BLUE RIDGE DUE TO THE INCREASED LOW LEVEL
CONVERGENCE. WILL STILL HAVE MOIST ATMOSPHERIC CONDITIONS TO
START THE DAY...HOWEVER MOISTURE WILL GRADUALLY DECREASE DURING
THE AFTERNOON AS DRIER AIR MOVES IN FROM THE NORTHEAST.

&&

SATURDAY NIGHT THROUGH MONDAY...
AS OF 245 PM EDT FRIDAY...

SURFACE WEDGE BECOMES FIRMLY ESTABLISHED SATURDAY NIGHT AND SUNDAY.
LOW LEVEL MOISTURE...ESPECIALLY ALONG AND JUST EAST OF THE BLUE
RIDGE DIMINISHED BY SUNDAY NIGHT. ENOUGH DRY AIR TO CUT BACK ON
PROBABILITY OF PRECIPITATION ON SUNDAY NIGHT AND CLOUD COVER FOR
MONDAY.

WILL KEEP MAXIMUM TEMPERATURES BELOW GUIDANCE FOR SUNDAY. MONDAY
WILL BE A BALANCE BETWEEN COOLER AIRMASS IN THE WEDGE AND AUGUST
SUN.

&&

MONDAY NIGHT THROUGH FRIDAY...
AS OF 1145 AM EDT FRIDAY...

DEEP UPPER TROF CROSSING THROUGH THE CENTRAL UNITED STATES
COMPLETELY FLATTENS THE SOUTHEAST RIDGE ON WEDNESDAY AND THURSDAY.
SPREAD OF SOLUTIONS ON MODELS BECOMES QUITE LARGE BY WEDNESDAY. WPC
WAS LEANING TOWARD THE LESS AMPLIFIED...MORE PROGRESSIVE EMCWF.

THE SURFACE HIGH THAT WEDGES DOWN THE APPALACHIANS STARTS OUT OVER
NEW ENGLAND...THEN BY WEDNESDAY THE PARENT HIGH MOVES OFFSHORE. BY
THAT TIME THE AMOUNT OF EASTERLY FLOW AND RIDGING WILL BE INFLUENCED
BY WHATEVER TROPICAL SYSTEM WILL BE FATHER EAST IN THE ATLANTIC.

A COLD FRONT OVER THE GREAT LAKES ON WEDNESDAY WILL APPROACH THE
FORECAST AREA LATE ON THURSDAY. MODELS SUGGEST NOT A LOT OF
SOUTHWARD PUSH OF THIS FRONT. BOUNDARY MAY STILL BE IN THE AREA ON
FRIDAY. AS THE SURFACE WEDGE BREAK DOWN AND THE FRONT
APPROACHES...850 MB TEMPERATURES WILL RISE.

FORECAST AREA WILL BE DRY AT MID AND UPPER LEVELS MONDAY NIGHT
THROUGH WEDNESDAY NIGHT. THEN BY THURSDAY DEEPER MOISTURE COMES BACK
INTO THE AREA ALONG THE FRONT. ECMWF EVEN SHOWED DRYING WELL BELOW
850 MB ON TUESDAY.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
AS OF 215 PM EDT FRIDAY...

CONTINUE TO OBSERVE LIGHT TO MODERATE SHOWER ACTIVITY MAKING ITS
WAY FROM SOUTHEAST WEST VIRGINIA...ACROSS KROA...THROUGH JUST
NORTH OF KDAN. HOWEVER...STRONGER CONVECTION IS OBSERVED
DEVELOPING ACROSS SOUTHERN WEST VIRGINIA...WHICH IS DRIFTING
SOUTHEAST TOWARD KBLF...WITH THESE CELLS TRAINING AS THEY
APPROACH.

THIS EVENING...WILL BE KEEPING AN EYE OUT FOR HEAVY RAIN ACROSS
THE MOUNTAINS...PARTICULARLY IN THE VICINITY OF KBLF...AND
POSSIBLY KBCB/KROA. BEST CHANCES FOR CONVECTION WILL BE FROM 22/20Z
THROUGH 23/00Z. WHILE GUSTY WINDS ARE POSSIBLE...MAIN THREAT WILL
BE HEAVY DOWNPOURS THAT WILL DROP VISIBILITIES TO LESS THAN 1/2SM
LOCALLY. VISIBILITIES WILL IMPROVE DRASTICALLY AS CONVECTION MOVES
OFF STATION.

SHOWERS WILL DECREASE IN COVERAGE OVERNIGHT...BUT WILL NOT
DISAPPEAR ALTOGETHER. EXPECT A RETURN OF MVFR/IFR CEILINGS ACROSS
THE MOUNTAINS...WHEREAS CEILINGS WILL REMAIN VFR ACROSS THE
PIEDMONT FOR MUCH OF THE NIGHT...BEFORE FALLING TO MVFR/IFR TOWARD
DAWN. HIGH PRESSURE WILL BUILD SOUTH FROM THE GREAT LAKES...
FINALLY PUSHING THE STALLED FRONTAL BOUNDARY THROUGH THE FORECAST
AREA FROM THE NORTHEAST TO FORM A WEDGING PATTERN. LOW LEVEL
CONVERGENCE ALONG THE BLUE RIDGE WILL TRIGGER MORE SHOWERS
SATURDAY AFTERNOON...HOWEVER THE ATMOSPHERE WILL GRADUALLY DRY
FROM THE NORTH AS THE HIGH SETTLES IN.

EXTENDED AVIATION...

EXPECT FLYING CONDITIONS TO SLOWLY IMPROVE SATURDAY NIGHT AND
SUNDAY AS HIGH PRESSURE CONTINUES TO BUILD IN FROM THE NORTHEAST.
WILL SEE A FEW SHOWERS DEVELOP ON SUNDAY AFTERNOON...HOWEVER THE
MAIN CONCERN WILL BE EARLY MORNING FOG AND STRATUS. STRATUS WILL
BE SLOW TO BURN OFF THROUGH THE DAY...ALTHOUGH BREAKS WILL DEVELOP
DURING THE AFTERNOON. A BETTER PUNCH OF DRY AIR WITH HIGH PRESSURE
BUILDING IN FROM THE NORTHEAST MAY BE ENOUGH WITH MIXING/HEATING
TO ALLOW FOR INCREASING VFR CONDITIONS MONDAY INTO TUESDAY UNDER
MAINLY DRY CONDITIONS.

&&

.EQUIPMENT...
THE ASOS AT LYNCHBURG (LYH) VA REMAINS PARTIALLY INOP DUE TO A
BOARD FAILURE. PARTS HAVE BEEN ORDERED WITH THE RETURN OF
COMPLETE SERVICE UNKNOWN AT THIS TIME.

&&

.RNK WATCHES/WARNINGS/ADVISORIES...
VA...FLASH FLOOD WATCH UNTIL 1 AM EDT SATURDAY FOR VAZ007-009>014.
NC...NONE.
WV...FLASH FLOOD WATCH UNTIL 1 AM EDT SATURDAY FOR WVZ042>045.

&&

$$
SYNOPSIS...NF
NEAR TERM...NF
SHORT TERM...AMS
LONG TERM...AMS
AVIATION...NF/PM
EQUIPMENT...


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