Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 201637 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1237 PM EDT SUN APR 20 2014 .SYNOPSIS...
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SLOW MOVING LOW PRESSURE OFF THE SOUTHEAST COAST WILL CONTINUE TO DRIFT EAST AND OFFSHORE THIS AFTERNOON. STRONG HIGH PRESSURE WILL BUILD INTO THE AREA FROM OFF THE MID ATLANTIC COAST THROUGH TONIGHT KEEPING DRY AIR IN PLACE INTO EARLY NEXT WEEK. ANOTHER COLD FRONT ARRIVES LATER TUESDAY WITH THE NEXT CHANCE OF SHOWERS AND STORMS.
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&& .NEAR TERM /THROUGH TONIGHT/... AS OF 930 AM EDT SUNDAY... LOW PRESSURE CONTINUES TO DRIFT EAST OFF S CAROLINA THIS MORNING WITH A GOOD SURGE OF DRIER AIR FROM THE NE ACROSS THE REGION PER MORNING RNK RAOB SHOWING A PWAT OF BELOW A QUARTER INCH. THIS DRY AIR AND DEEP NE FLOW HAS ALREADY ACTED TO MIX OUT MOST CLOUD COVER EXCEPT FOR SOME LINGERING CI NORTH AND OVER THE FAR SE WHERE CLOSER TO THE DEEPER MOISTURE AXIS AROUND THE SYSTEM. MAY STILL SEE SOME INTERVALS OF HIGH CLOUDS THROUGH THE AFTERNOON...OTRW THINKING MAINLY SUNNY/COMFORTABLE UNDER LOWERING DEWPOINTS WITH A GUSTY NE WIND LINGERING EASTERN SECTIONS AS THE GRADIENT PERSISTS A BIT LONGER. MORNING THICKNESS GIVEN HEATING OF DRY AIR...AND GRADUAL EROSION OF THE 85H COOL POCKET SUPPORTS UNIFORM HIGHS IN THE 60S...WITH PERHAPS SOME SPOTS GETTING TO AROUND 70 LATE SO BUMPED UP TEMPS A LITTLE IN SPOTS. PREVIOUS DISCUSSION AS OF 345 AM EDT SUNDAY... A FEW SPRINKLES/SPOTTY LIGHT RAIN WERE STILL OBSERVED ON RADAR ACROSS THE NORTHERN PIEDMONT OF NORTH CAROLINA. THIS REGION REMAINS UNDER THE INFLUENCE OF THE NORTHERN PERIPHERY OF THE DEPARTING UPPER LOW OFF THE SOUTHEAST U.S. COAST. GFS ILLUSTRATED THIS AREA OF PRECIP WELL IN ITS 700MB-300MB OMEGA FORECAST WHICH IS PUSHED EAST BY 12Z. IN ADDITION...DRIER AIR CONTINUES TO INFILTRATE OUR AREA UNDER A WEAK NORTHEAST FLOW WITH DEW POINTS FALLING THROUGH THE EARLY MORNING HOURS. AS RESULT...ANY LIGHT PRECIP ACROSS THE SOUTHEAST PORTION OF THE FORECAST AREA EARLY THIS MORNING WILL CONTINUE TO WANE AND DRY CONDITIONS ARE EXPECTED REGION-WIDE LATER THIS MORNING. DISCOUNTED THE 00Z NAM SOLUTION WHICH TRIES TO SURGE 850MB THETA-E AIR BACK INTO THE FORECAST AREA WITH A MORE EASTERLY COMPONENT TO THE WIND. AS AN UPPER RIDGE GRADUALLY BUILDS TODAY...CLOUDS WILL THIN FROM WEST TO EAST ALLOWING SKIES TO BECOME MOSTLY SUNNY. CLEARING WILL BE DELAYED IN THE FAR SOUTHEAST UNTIL AFTER 18Z WHEN LAST PIECE OF UPPER LEVEL ENERGY FINALLY EXITS. MOSTLY SUNNY SKIES WILL HELP MIX DOWN 15-25KT 850MB WINDS AND DRIER AIR WHICH MAY RESULT IN SOME PERIODIC WIND GUSTS. ALSO LOWERED DEW POINTS WITH THIS MIXING. BOTH THE GFS AND NAM MOS HAVE SHOWN A WARM BIAS UNDER THIS MAINLY DRY WEDGE PATTERN. WITH MORE SUN EXPECTED LATER TODAY...READINGS SHOULD BE A COUPLE OF DEGREES WARMER COMPARED TO SATURDAY...BUT STILL UNDERCUT THE GFS/NAM MOS VALUES BY A COUPLE OF DEGREES. WEAK SFC RIDGE BUILDS OVER THE AREA TONIGHT WHICH ALLOWS WINDS TO DIMINISH. THIS...COMBINED WITH MOSTLY CLEAR SKIES SHOULD ALLOW TEMPS TO FALL TO THE COOLER GFS MOS VALUES. CANNOT RULE OUT SOME PATCHY FROST TONIGHT IN THE MOUNTAIN VALLEYS. && .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... AS OF 345 AM EDT SUNDAY... RIDGING IN THE UPPER LEVELS OF THE ATMOSPHERE WILL BEGIN TO TAKE SHAPE ON MONDAY...ALLOWING WINDS ALOFT TO SHIFT MORE SOUTHWESTERLY. DESPITE SURFACE HIGH PRESSURE STILL WEDGED AGAINST THE EASTERN FACE OF THE APPALACHIANS AND INCREASING MID AND HIGH CLOUDS THROUGH THE DAY...THE UPPER RIDGING WILL ALLOW AFTERNOON TEMPERATURES TO WARM A FEW DEGREES OVER THOSE FROM SUNDAY...WITH HIGHS CLIMBING INTO THE LOW 70S. BY LATE EVENING...SURFACE WINDS WILL BEGIN TO SHIFT SOUTHWESTERLY AHEAD OF AN APPROACHING COLD FRONT. EXPECT WARMER RIDGELINES COMPARED TO THE VALLEY BOTTOMS...WITH OVERNIGHT LOWS GENERALLY IN THE 40S AND THE LOW 50S. FOR TUESDAY...A SURFACE TROUGH WILL DEVELOP ALONG THE LEE OF THE BLUE RIDGE. THE LOW LEVEL CONVERGENCE OF THE TROUGH WILL COMBINE WITH STRONG DAYTIME HEATING TO TRIGGER SCATTERED SHOWERS AND SOME THUNDERSTORMS DURING THE AFTERNOON AND EVENING...WITH THE CHANCE THAT ONE OR TWO STORMS MAY BECOME STRONG TO SEVERE DURING EARLY EVENING. WITH ANY STRONG STORMS THAT DO DEVELOP...WOULD SAY THE MAIN CONCERNS WOULD BE LOCALLY GUSTY WINDS DUE TO DRY LOW LEVELS OF THE ATMOSPHERE...AND MODEST INSTABILITY THAT WILL ALSO SUPPORT SOME HAIL. INSTABILITY WILL FALL OFF QUICKLY DURING THE EVENING AS WINDS SHIFT INCREASINGLY WEST TO NORTHWESTERLY...AND SHOWERS AND THUNDERSTORMS SHOULD FADE AROUND SUNSET. THE COLD FRONT WILL PASS QUICKLY ACROSS THE AREA DURING THE EVENING...EXITING TO THE EAST AFTER MIDNIGHT. DRY CONDITIONS ARE EXPECTED FOR WEDNESDAY AS HIGH PRESSURE PASSES ACROSS THE GREAT LAKES...MAINTAINING A COOLER NORTHERLY WIND FLOW. REGARDLESS...WITH ABUNDANT SUNSHINE AND ANOTHER UPPER LEVEL RIDGE APPROACHING FROM THE WEST...WILL SEE AFTERNOON HIGHS RANGE FROM AROUND 60 ACROSS SOUTHEAST WEST VIRGINIA...TO AROUND 70 ACROSS THE SOUTHSIDE. STRONG RADIATIONAL COOLING MAY ALLOW FOR SOME FROST TO DEVELOP IN THE MOUNTAIN VALLEYS WEDNESDAY NIGHT. && .LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 1245 PM EDT SATURDAY... SURFACE HIGH PRESSURE WILL CONTINUE TO SHIFT EAST ON THURSDAY AND BECOME SITUATED OFF THE EAST COAST BY FRIDAY. AN UPPER LEVEL RIDGE WILL CONTINUE TO BUILD OVER THE APPALACHIANS WHILE STRENGTHENING SOUTHWEST FLOW ALLOWS FOR GOOD WARM AIR ADVECTION. EXPECT THURSDAY TO CONTINUE TO BE A PERIOD OF NO PRECIPITATION AND MODERATING TEMPERATURES. A COLD FRONT WILL APPROACH THE AREA THURSDAY NIGHT AND CROSS THE REGION FRIDAY INTO FRIDAY NIGHT. ANTICIPATE TEMPERATURES TO REMAIN MILD IN ADVANCE OF THE FRONT THURSDAY NIGHT INTO FRIDAY...BUT WITH INCREASING CLOUD COVER AND CHANCES OF SHOWERS. MODEL GUIDANCE CURRENTLY OFFERS THE POTENTIAL FOR SOME CONVECTIVE WEATHER WITH THE PASSAGE OF THE FRONT. HAVE INCLUDED A SLIGHT CHANCE OF THUNDERSTORMS ACCORDINGLY ON FRIDAY. COOLER AIR ARRIVES FRIDAY NIGHT INTO SATURDAY...WHILE LINGERING RAIN SHOWERS DECREASE IN COVERAGE...ENDING LAST ACROSS SOUTHEAST WEST VIRGINIA WHERE UPSLOPE CONDITIONS WILL MAINTAIN THE PRECIPITATION THE LONGEST. && .AVIATION /16Z SUNDAY THROUGH THURSDAY/...
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AS OF 1215 PM EDT SUNDAY... GOOD FLYING WEATHER WILL CONTINUE UNDER VFR CONDITIONS INTO MONDAY WITH HIGH PRESSURE EXTENDING ACROSS THE REGION FROM THE MID ATLANTIC COAST. MAY SEE SOME PERIODIC HIGH CLOUDS ESPCLY AROUND DAN INTO THIS EVENING WITH ANY LOWER CIGS LIKELY REMAINING TO THE SE OVERNIGHT AS VERY DRY AIR CONTINUES TO ADVECT IN. WIND GUSTS COULD REACH 20-25 KTS ACROSS THE EASTERN SITES THIS AFTERNOON WHERE THE PRESSURE GRADIENT WILL LINGER BETWEEN THE EXITING LOW TO THE SE AND THE HIGH TO THE NORTH. EXPECT LIGHTER SPEEDS ELSW ON THE ORDER OF 10-20 KTS WITH A GRADUAL DECREASE LATER THIS AFTERNOON FOLLOWED BY LIGHT/VRBL WINDS OVERNIGHT INTO MONDAY. EXTENDED AVIATION DISCUSSION... THE NEXT COLD FRONT APPROACHES MONDAY NIGHT WITH MORE SHOWERS AND POSSIBLE THUNDERSTORMS...WITH LOCALIZED MVFR FLIGHT RESTRICTIONS ON TUESDAY. THE FRONT EXITS TUESDAY NIGHT...RESULTING IN A RETURN TO VFR WEATHER AND GUSTY NW WINDS ON WEDNESDAY...EXCEPT FOR THE POTENTIAL OF SOME MVFR CIGS OVER THE FAR WESTERN UPSLOPE SITES IN SE WEST VA. HIGH PRESSURE BUILDS IN FOR THURSDAY...WITH WIDESPREAD VFR LIKELY.
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&& .FIRE WEATHER... AS OF 945 AM EDT SUNDAY... THE COMBINATION OF DRY/GUSTY EASTERLY FLOW AND HEATING WILL CAUSE AFTERNOON HUMIDITY LEVELS TO FALL BELOW 30 PERCENT MAINLY OVER THE MOUNTAINS. THIS DRYING AND STRONG HEATING WILL ALSO ALLOW FUEL MOISTURE LEVELS TO QUICKLY DECREASE ESPCLY IN AREAS THAT DID NOT SEE ANY RAINFALL ON SATURDAY. HOWEVER WIND SPEEDS ARE EXPECTED TO SLOWLY DIMINISH THIS AFTERNOON OVER THE WESTERN MOUNTAINS IN SE WVA WHERE PARAMETERS ARE MORE CRITICAL...WITH SUSTAINED VALUES DROPPING BELOW 10-15 MPH. THUS WILL HEADLINE THE FIRE WEATHER FORECAST FOR LOWERING HUMIDITY AND GUSTY WINDS THIS AFTERNOON BUT HOLD OFF ON ANY STATEMENTS PENDING CONDITIONS OVER FAR WESTERN SECTIONS EARLY THIS AFTERNOON. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/PH NEAR TERM...JH/PH SHORT TERM...NF LONG TERM...NF AVIATION...JH/PH/WERT FIRE WEATHER...JH

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