Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 180858 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 458 AM EDT FRI APR 18 2014 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN ACROSS THE NORTHEAST U.S. THROUGH SATURDAY...WHILE AN AREA OF LOW PRESSURE DEVELOPS AND MOVES SLOWLY EAST THROUGH THE SOUTHEAST STATES...MOVING OFF THE SOUTHEAST U.S. COAST MONDAY. THIS SYSTEM WILL BRING LIGHT RAIN TO THE SOUTHERN PORTIONS OF THE FORECAST AREA TONIGHT AND SATURDAY. AN UPPER TROUGH AND ASSOCIATED COLD FRONT WILL MOVE THROUGH THE REGION FROM THE WEST EARLY NEXT WEEK WITH THE NEXT CHANCE FOR SHOWERS AND POSSIBLY THUNDERSTORMS.
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&& .NEAR TERM /THROUGH TONIGHT/...
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AS OF 445 AM EDT FRIDAY... INCREASINGLY COMPLICATED FORECAST THROUGH THE NEAR TERM THANKS TO DEEPENING LOW PRESSURE AREA ALOFT ACROSS THE SOUTHEAST STATES. MODELS IN GENERAL AGREEMENT ON SYNOPTIC PATTERN...BUT QPF AND NORTHWARD EXTENT OF PCPN PROBLEMATIC. GFS BRINGS OVER AN INCH OR RAIN AS FAR NORTH AS SOUTHERN VA OVERNIGHT...WHILE NAM/ECMWF/CANADIAN KEEP PCPN AMOUNTS TO AROUND 1/4 INCH IN SOUTHERN VA AND PERHAPS UP TO 1/2 INCH IN NC COUNTIES. GFS HAS BEEN CONSISTENT LAST SEVERAL RUNS IN DEVELOPING A BAND OF HEAVIER RAIN ACROSS SW/SC VA...BUT THIS HAS NEVER BEEN INDICATED BY THE OTHER MODELS. WPC INDICATES GFS IS ODD SOLUTION AND AS A RESULT HAVE CHOSEN TO DISCARD HEAVIER RAINFALL AND FURTHER NORTHWARD EXTENT...EVEN INTO WV...INDICATED BY GFS. NONETHELESS...ALL MODELS HAVE TRENDED WETTER...FURTHER NORTH...WITH -RA POSSIBLY BEGINNING IN WESTERN NC EVEN LATE THIS AFTERNOON. EXTENSIVE HIGH CLOUD COVER HAS ALREADY OVERSPREAD THE REGION...AND SOME LOW CLOUDS CREEPING INTO EASTERN PIEDMONT COUNTIES. TEMPERATURES WILL RISE VERY LITTLE TODAY AND BE QUITE UNIFORM ACROSS THE REGION THROUGH THE NEAR TERM...MAINLY 50S FOR HIGHS TODAY AND 40S FOR LOW TONIGHT...WITH A FEW LOW 60S POSSIBLE IN FAR SW VA. E-NE FLOW WILL TEND TO KEEP AREAS EAST OF THE ALLEGHANY FRONT COOLER THAN NORMALLY COLDER WESTERN AREAS. MODEL GUIDANCE SIMILAR AND INTERESTING TO NOTE THAT ECMWF GRIDDED OVERNIGHT TEMPS NEAR 45 ACROSS ENTIRE CWA. WITH RESPECT TO FROST ADVISORY...HAVE CANCELLED ALL EXCEPT FOR A FEW OF THE ORIGINAL INCLUDED COUNTIES AS CLOUDS AND EAST FLOW HAVE PREVENTED DECOUPLING. IT NEVER EVEN GOT BELOW 40 AT DAN/LYH AS A RESULT. OPTED TO KEEP THE SOUTHERN SHENANDOAH VALLEY COUNTIES IN THROUGH 8 AM AS MESO OBS SHOW READINGS IN THE LOW 30S THERE YET WITH CALM WINDS...SO FROST QUITE LIKELY THERE.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
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AS OF 230 AM EDT FRIDAY... SATURDAY MORNING...ONSHORE FLOW IN ASSOCIATION WITH A SLOW MOVING AREA OF LOW PRESSURE OVER GEORGIA IS STILL EXPECTED TO BE BRINGING PATCHY LIGHT RAIN TO THE SOUTHERN THIRD OF THE FORECAST AREA. AS THE DAY PROGRESSES...THE LOW WILL SHIFT SLOWLY EASTWARD...AND LIKEWISE WILL THE PRECIPITATION. CLOUD COVER ALSO WILL DECREASE IN COVERAGE FROM NORTHWEST TO SOUTHEAST. BY EARLY SATURDAY EVENING...THE PRECIPITATION IS EXPECTED TO OUT OF THE AREA...WITH THE CLOUD COVER CONTINUING TO EXIT. FOR HIGHS ON SATURDAY...HAVE FAVORED NUMBERS AROUND OR SLIGHTLY COOLER THAN THAT OF THE MAV MOS GIVEN THE NAM HAS SOLUTION WITH LESS CLOUD COVER AND PRECIPITATION. LIKEWISE FOR SATURDAY NIGHT...HAVE LEANED MORE TOWARD THE MAV MOS GUIDANCE. HEADING INTO SUNDAY...THE CLOSED LOW OVER THE SOUTHEAST U.S. CONTINUES ITS PROGRESSION EASTWARD INTO THE ATLANTIC. OVER OUR REGION...HIGH PRESSURE WILL BUILD OVERHEAD CONCURRENT TO AN UPPER RIDGE DEVELOPING OVER THE EASTERN U.S. THE RESULT WILL BE A PRECIPITATION-FREE FORECAST ON SUNDAY AND MONDAY WITH A TREND TOWARD MODERATING TEMPERATURES.
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&& .LONG TERM /TUESDAY THROUGH THURSDAY/... AS OF 330 PM EDT WEDNESDAY... MONDAY LOOKS TO BE DRY WITH THE ATLANTIC SYSTEM WELL OUT TO SEA AND A WEAK RIDGE OF HIGH PRESSURE ALONG THE EASTERN SEABOARD AND SEASONAL TEMPERATURES. MODELS BRING A FAIRLY STRONG FRONT THROUGH THE CWA ON TUESDAY WITH GOOD CHANCES FOR SHOWERS AND POSSIBLE THUNDERSTORMS DEPENDING ON MESOSCALE FORCING IN PLACE AT THAT TIME. SKIES SHOULD CLEAR TUESDAY NIGHT INTO WEDNESDAY WITH NORTHWEST FLOW AND COOLER TEMPS BEHIND THE FRONT. && .AVIATION /09Z FRIDAY THROUGH TUESDAY/... AS OF 200 AM EDT FRIDAY... MODEL SOLUTIONS PRESENTING SOME CHALLENGES IN THE LATER PORTIONS OF THE TAF VALID PERIODS...BUT FOLLOWING WPC LEAD IN THROWING OUT GFS SOLUTION WHICH BRINGS MOISTURE FROM DEVELOPING CLOSED UPPER LOW SOUTHEAST U.S. TOO FAR NORTH AS WELL AS TOO SOON...AND AS A RESULT HAS IFR OR WORSE CIGS AND -RA IN THE CENTRAL/SOUTHERN PARTS OF OUR CWA AS EARLY AS LATE AFTERNOON. THUS...LEANING TOWARD EARLIER 12Z ECMWF OR 00Z NAM...WILL KEEP VFR CONDITIONS IN PLACE THROUGH THE TAF VALID PERIOD. NONETHELESS...EXTENSIVE HIGH AND EVENTUALLY MID CLOUDS WILL OVERSPREAD THE CWA FROM THE SOUTH AND WEST. HAVE KEPT ALL CIGS VFR THROUGH THE TAF VALID PERIOD...WITH NO ISSUES WITH VSBY AS NO PCPN EXPECTED THROUGH THE TAF VALID PERIOD. FOR WINDS...A GENERAL ESE-NE FLOW WILL CONTINUE...GENERALLY ESE WEST OF THE BLUE RIDGE AND NE EAST OF THE BLUE RIDGE. AS SFC LOW PRESSURE DEEPENS ACROSS THE SOUTHEAST WITH TIME...EXPECT WINDS TO COME AROUND MORE TO THE NE AND INCREASE IN SPEED. THROUGH 00Z...LOOK MOSTLY FOR 5-7KT WINDS...EXCEPT BLF WHERE SOME LOW END GUSTS STILL POSSIBLE. AFT 00Z...WINDS 6-10KTS...STRONGER WINDS EAST OF THE BLUE RIDGE. MEDIUM TO HIGH CONFIDENCE IN CIGS/VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND SPD/DIR THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... EVENTUALLY -RA AND MVFR TO POSSIBLY IFR CIGS WILL CREEP INTO THE SE PART OF THE CWA SATURDAY. LWB AND POSSIBLY EVEN BLF SHOULD REMAIN VFR MOST OF THIS TIME...BUT SOME MVFR POSSIBLE AT BLF. STILL MANY UNCERTAINTIES REGARDING SE U.S. UPPER LOW AND IMPACT ON AVIATION CONDITIONS ACROSS THE REGION...BUT MAIN IMPACT SHOULD CLEARLY BE FOR DAN/LYH/ROA AT THIS POINT. AS THAT SYSTEM EXITS TO THE EAST SUNDAY AND HIGH PRESSURE RETURNS FOR THE REMAINDER OF THE WEEKEND...EXPECT VFR CONDITIONS TO RETURN. THE NEXT SYSTEM TO BRING MVFR TO POTENTIALLY IFR CIGS AND -SHRA TO THE AREA DOES NOT ARRIVE UNTIL EARLY TO MID PART OF NEXT WEEK. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...FROST ADVISORY UNTIL 8 AM EDT THIS MORNING FOR VAZ023-024-035- 047. NC...NONE. WV...NONE.
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&& $$ SYNOPSIS...RAB NEAR TERM...KK/KM/RAB SHORT TERM...DS LONG TERM...PC AVIATION...KK/RAB

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