Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 261149 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 749 AM EDT SUN APR 26 2015 .SYNOPSIS... WITH THE DEPARTURE OF AN UPPER LEVEL SYSTEM FROM THE MID ATLANTIC THIS MORNING...HIGH PRESSURE BUILDING IN FROM THE MIDWEST REGION WILL BECOME THE MAIN WEATHER FEATURE FOR OUR AREA TODAY. ANOTHER LOW PRESSURE SYSTEM IS EXPECTED TO AFFECT THE SOUTHEAST AND MID ATLANTIC REGION DURING THE MIDDLE OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 345 AM EDT SUNDAY... KEEPING AN EYE ON AN AREA OF RAIN...WITH THE OCCASIONAL EMBEDDED THUNDERSTORM...MAKING ITS WAY EAST ACROSS CENTRAL VIRGINIA THIS MORNING AS AN UPPER LEVEL DISTURBANCE MOVES ACROSS THE REGION. RAPID UPDATE MODELS INDICATE THAT THE MAJORITY OF THIS RAIN WILL EXIT OUR AREA FOR THE COASTAL PLAIN BY 7 AM...LEAVING ONLY ISOLATED SHOWERS...WHICH WILL BE INTERMIXED WITH AREAS OF FOG AND DRIZZLE THROUGH LATE MORNING. WITH THE DEPARTURE OF THE UPPER LEVEL DISTURBANCE...HIGH PRESSURE BUILDING IN FROM THE MIDWEST STATES WILL GRADUALLY TAKE OVER AS OUR DOMINATING WEATHER FEATURE...CAUSING WINDS ACROSS OUR AREA TO SLOWLY SHIFT NORTHWEST THROUGH THE DAY. THE VERY SLOW ARRIVAL OF DRIER AIR MEANS THAT LOW CLOUDS WILL REMAIN ACROSS OUR FORECAST AREA THROUGH MUCH OF THE DAY...KEEPING A FIRM LID ON DAYTIME HEATING. ALTHOUGH SLIGHTLY WARMER THAN THOSE OBSERVED ON SATURDAY...HIGH TEMPERATURES THIS AFTERNOON WILL REMAIN WELL BELOW NORMAL FOR LATE APRIL... GENERALLY HOLDING IN THE LOW TO MID 50S MOST LOCATIONS...WITH UPPER 40S POSSIBLE IN A FEW SPOTS NEAR THE INTERSTATE 64 CORRIDOR. CLOUDS WILL START TO BREAK UP DURING LATE AFTERNOON/EARLY EVENING EAST OF THE BLUE RIDGE...WITH CLOUD COVER DECREASING ACROSS THE MOUNTAINS AFTER DARK. THE ARRIVAL OF HIGH PRESSURE WILL ALSO CAUSE THE PRESSURE GRADIENT TO INCREASE FOR THE CENTRAL APPALACHIANS...AND WE CAN EXPECT WINDS TO BECOME BREEZY AFTER MIDNIGHT. LOOKING ONCE AGAIN AT ANOTHER COOL NIGHT...WITH SUNDAY NIGHT LOWS RANGING FROM THE MID 40S ACROSS THE FOOTHILLS IN NORTH CAROLINA...TO THE LOW AND MID 30S ALONG THE INTERSTATE 64 CORRIDOR. MAY BE A FEW SPOTS WHERE TEMPERATURES FALL BELOW FREEZING IN THE NORTH...HOWEVER THE INCREASED WIND SPEEDS WILL LIKELY PREVENT FROST FORMATION. WILL LET THE DAY SHIFT TAKE A LOOK AT ANOTHER BATCH OF MODEL DATA...AND DETERMINE IF ANY FROST/FREEZE STATEMENTS ARE NECESSARY FOR TONIGHT. && .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... AS OF 400 AM EDT SUNDAY... CONVOLUTED UPPER AIR PATTERN REMAINS IN PLACE THROUGH THE PERIOD. THE MAIN FEATURES BEING A DEEP 529DM UPPER LOW OFF THE NORTHEAST U.S. COAST EXTENDING WELL BACK INTO THE OH VALLEY/MID-ATLANTIC REGION...A CLOSED LOW COMING OUT OF THE DESERT SOUTHWEST INTO TEXAS...AND A ELONGATED RIDGE IN BETWEEN BETWEEN THE CENTRAL CANADIAN PROVINCES DOWN INTO THE CENTRAL U.S...THEN THE SOUTHEAST U.S. FOR MON AND TUE...OUR REGION WILL REMAIN LARGELY UNDER THE INFLUENCE OF THE NORTHEAST U.S./NORTHERN MID-ATLANTIC UPPER LOW. A SPOKE OF PVA/SHORT WAVE WILL ROTATE THROUGH THE REGION FROM THE NORTH ON THE WEST SIDE OF THE ELONGATED UPPER LOW. WITH 850MB TEMPS CONTINUING TO HOVER NEAR 0C AND COLD 500MB TEMPS -20 TO -24C... THE ATMOSPHERE WILL BE QUITE UNSTABLE. ANY MORNING SUNSHINE WILL QUICKLY RESULT IN CU/SC DEVELOPING AND LIKELY -SHRA ACROSS THE MOUNTAINS BY LATE MORNING THROUGH THE EARLY EVENING. TEMPERATURES WILL REMAIN WELL BELOW NORMAL...AND ANY SHOWERS WILL EASILY BRING THOSE AREAS BACK DOWN INTO THE 40S DURING THE AFTERNOON. IN FACT...850MB TEMPS COULD SUPPORT SOME -SN AT THE HIGHEST ELEVATIONS MON MORNING...BUT HAVE NOT INCLUDED IN THE GRIDS AT THIS TIME. SHOWERS WILL BE CONSIDERABLY LESS LIKELY IN THE DOWNSLOPE PIEDMONT AREAS. LESS CLOUDS IN THIS AREA WILL ALSO ALLOW MAX TEMPS TO WARM BACK INTO THE 60S...YET STILL BELOW NORMAL. FOR TUE...THE DEEP UPPER LOW FINALLY BEGINS TO DRIFT EAST FURTHER OUT TO SEA...WHILE THE UPPER LOW ACROSS TX DRIFTS INTO THE ARKLATEX REGION. A NEW UPPER LOW BEGINS TO DRIFT SOUTH OUT OF THE CENTRAL CANADIAN PROVINCES...WHILE THE SKINNY/COMPLICATED UPPER RIDGE DRIFTS INTO OUR REGION. THIS SHOULD BE THE ONE DAY WITH LITTLE TO NO -SHRA ACTIVITY WITH NO FORCING EVIDENT ALOFT AND WEAK RIDGING. INCREASED SUNSHINE SHOULD ALLOW TEMPS TO WARM A TAD CLOSER TO NORMAL...BUT 850MB TEMPS ONLY WARM A FEW DEGREES TO ABOUT +4C ACROSS MUCH OF THE CWA. FOR WED...THE ARKLATEX UPPER LOW DRIFTS INTO THE SOUTHEAST STATES WHILE LOW PRESSURE ALOFT DRIFTS SOUTHWARD INTO THE GREAT LAKES. THESE TWO SYSTEM WILL MERGE ACROSS THE REGION INTO THU AS YET ANOTHER UPPER LOW FORMS ACROSS THE MID-ATLANTIC BY THU. LIGHT RAIN WILL BEGIN TO SPREAD INTO THE REGION WED AS HEIGHTS ALOFT LOWER AS THE UPPER LOWS CONVERGE ACROSS THE REGION. THIS...ALONG WITH CLOUD COVER AND INCREASED PRECIPITATION WILL ENSURE CONTINUED WELL BELOW NORMAL TEMPERATURES. QPF DOES NOT APPEAR TO BE AN ISSUE AT THIS POINT AS THE HEAVIEST RAINFALL WILL REMAIN WELL SOUTH OF THE REGION. && .LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 430 AM EDT SUNDAY... THE GFS AND CANADIAN HAVE COME INTO BETTER AGREEMENT WITH THE ECMWF ON DEVELOPMENT AND EVOLUTION OF A COASTAL LOW/ALMOST MILLER-A TYPE SETUP OFF THE SOUTHEAST U.S. COAST THU. THIS WILL SPREAD RAIN INTO THE REGION FROM THE SOUTH. AS THE SOUTHERN STREAM LOW BECOMES ABSORBED INTO SOUTHWARD MOVING UPPER LOW FROM THE GREAT LAKES...A DEEP 540DM UPPER LOW WILL EVOLVE ACROSS WV/VA INTO EARLY FRI. THIS WILL PROLONG THE LIGHT RAIN...NORTHERLY FLOW...AND UNSEASONABLY COOL TEMPERATURES RIGHT INTO FRI. WITH THE REGION LARGELY UNDER A COOL/STABLE/NORTHERLY FLOW...PWATS ACROSS THE REGION ARE GENERALLY AROUND 1/2 INCH DURING THIS TIME FRAME...SO HEAVY RAIN DOES NOT APPEAR TO BE A CONCERN. THAT SHOULD REMAIN WELL SOUTHEAST ALONG COASTAL AREAS AND THEN OFF THE VA/MD COAST WITH TIME. BUT...850MB TEMPS WILL CONTINUE TO HOVER NEAR 0C THROUGHOUT THE PERIOD AS THE UPPER LOW DUMBBELLS ACROSS THE MID- ATLANTIC...KEEPING MAX TEMPS FOR SURE WELL BELOW NORMAL...BUT MIN TEMPS SLIGHTLY BELOW NORMAL BECAUSE OF CLOUD COVER && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... AS OF 745 AM EDT SUNDAY... DEEP UPPER LOW OFF THE NORTHEAST U.S. COAST WILL SINK SLOWLY SOUTHWARD TO OFF THE MID-ATLANTIC COAST BY MONDAY. ASSOCIATED WEST-EAST ORIENTED FRONTAL BOUNDARY FROM TYS-RDU...WILL SINK SLOWLY SOUTH AS WELL. WRAP AROUND -SHRA WILL CONTINUE ACROSS THE CWA WITH WEAK FORCING FROM THE NORTH ON BACK SIDE OF UPPER LOW. DOUBLE BARREL SFC LOW...ONE IN THE EASTERN TN VALLEY AND THE OTHER OFF THE NC COAST WILL SHIFT SOUTHEAST WITH TIME. WINDS WILL BACK FROM NE TO NW THROUGH THE TAF VALID PERIOD. THIS WILL KEEP A MOIST ATLANTIC FLOW EAST OF THE BLUE RIDGE UNTIL EVENING AND A MOIST UPSLOPE FLOW WEST OF THE BLUE RIDGE. -SHRA WILL CONTINUE THROUGHOUT THE DAY...BUT GRADUALLY DIMINISH AND SHIFT SOUTHEAST BY AFTERNOON. WILL DROP DEFINITE -SHRA FROM FM GROUPS AFT 18Z...BUT INCLUDE VCSH THROUGH THE REMAINDER OF THE AFTERNOON. IFR-LIFR CIGS THROUGH 15Z WILL GRADUALLY IMPROVE TO MVFR BY EARLY-MID AFTERNOON EAST OF THE BLUE RIDGE...BUT LIKELY ONLY TO IFR TO LOW END MVFR WEST OF THE BLUE RIDGE IN UPSLOPE FLOW. VSBYS GENERALLY NOW VFR EAST OF THE BLUE RIDGE...BUT LINGERING MVFR-IFR WEST OF THE BLUE RIDGE. EXPECT MOST AREAS TO IMPROVE TO VFR BY LATE MORNING/EARLY AFTERNOON...WITH THE EXCEPTION OF BLF WHICH COULD LINGER WITH IFR-MVFR VSBYS MUCH LONGER...AND WHICH MAY RETURN AFT 00Z. WILL NEED TO WATCH SPOKE OF PVA/SHORT WAVE APPROACHING FROM THE NORTH LATE TONIGHT WITH POSSIBLE RENEWED SHOWER ACTIVITY ACROSS THE MOUNTAINS OF WV AT THAT TIME. WINDS NE 5-7KTS THROUGH MID- DAY...BACKING TO NW 6-8KTS DURING THE AFTERNOON/EVENING. MEDIUM CONFIDENCE IN CIGS AND VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM CONFIDENCE IN WIND DIR/SPD THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... BREEZY NORTHWEST FLOW IS EXPECTED FOR MONDAY AND EARLY TUESDAY AS HIGH PRESSURE BUILDS IN FROM THE NORTHWEST. AS NOTED ABOVE...A SHORT WAVE WILL ROTATE AROUND THE BACK SIDE OF THE NORTHERN ATLANTIC UPPER LOW...WHICH WILL KEEP VARIABLE CLOUDS AND SCT -SHRA ACROSS THE MOUNTAINS...ESPECIALLY DURING PEAK HEATING. MVFR CIGS MAY LINGER IN THESE AREAS...BUT VFR CIGS TO NO CIGS ARE EXPECTED ACROSS THE PIEDMONT. WINDS WILL BE NORTHWEST 5-10KTS...WITH SOME LOW END GUSTS POSSIBLE WEST OF THE BLUE RIDGE. VFR CONDITIONS ARE EXPECTED TUE BEFORE CONDITIONS WORSEN ONCE AGAIN WED-THU AS A LOW PRESSURE SYSTEM PASSES ACROSS THE SOUTHEAST STATES...WHICH WILL AFFECT THE MID ATLANTIC ON WEDNESDAY INTO THURSDAY. CONFIDENCE IS GROWING THAT THIS SYSTEM WILL RESULT IN WIDESPREAD RAIN FOR THE FORECAST AREA...AS WELL AS PERSISTENT MVFR/IFR CONDITIONS. AN UPPER LOW WILL ALSO BUILD SOUTHWARD FROM THE GREAT LAKES AT THE SAME TIME. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...NF NEAR TERM...NF SHORT TERM...RAB LONG TERM...PM/RAB AVIATION...AMS/NF/RAB

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