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...
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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.
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&& .NEAR TERM /THROUGH SATURDAY/...
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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.
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&& 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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