Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 251424 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1024 AM EDT SAT APR 25 2015 .SYNOPSIS... HIGH PRESSURE WILL CONTINUE TO SHIFT OFF THE COAST TODAY AS A LOW PRESSURE SYSTEM PUSHES EAST FROM THE CENTRAL PLAINS...BRINGING RAIN TO THE CENTRAL APPALACHIANS TODAY AND TONIGHT. THE SYSTEM WILL EXIT TO THE EAST SUNDAY MORNING...WITH HIGH PRESSURE BUILDING IN FROM THE WEST DURING THE AFTERNOON. ANOTHER LOW PRESSURE SYSTEM IS EXPECTED TO AFFECT THE SOUTHEAST AND MID ATLANTIC REGION DURING THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 1015 AM EDT SATURDAY... NAM BUFKIT SOUNDING WAS IN GOOD AGREEMENT WITH 12Z RNK SOUNDING... WHICH WAS IN THE SAME BALLPARK AS GFS SO HAVE GOOD CONFIDENCE IN MODEL SOLUTIONS THROUGH THE NEAR TERM. ABUNDANT MOISTURE AND ISENTROPIC LIFT RUNNING OVER THE SURFACE WEDGE OF COOL AIR WILL KEEP PERIODS OF RAIN GOING THROUGHOUT THE AFTERNOON. INSTABILITY AND DYNAMIC ENVIRONMENT BECOME FAVORABLE FOR SIGNIFICANT STORMS TO OUR WEST AS INDICATED BY SPC PRODUCTS...BUT AS THE STORMS DEVELOP AND MOVE IN OUR DIRECTION LATE THIS AFTERNOON THEN WILL ENCOUNTER THE COOL STABLE AIR IN PLACE OVER OUR REGION AND WILL NOT POSE A THREAT FOR SEVERE WEATHER...THOUGH EXTREME WEST AND SOUTH MAY HEAR A RUMBLE OR TWO OF THUNDER. THE COOL WEDGE WILL KEEP TEMPS 15 TO 20 DEGREES BELOW NORMAL TODAY. THIS IS ALL IN GOOD AGREEMENT WITH THE CURRENT SET OF GRIDS SO ONLY SOME MINOR ADJUSTMENTS TO FINE TUNE CURRENT CONDITIONS ARE NECESSARY. APPLICABLE PORTION OF PREVIOUS AFD... CANNOT RULE OUT LOCALLY HEAVY RAIN ACROSS THE MOUNTAINS DURING LATE THIS AFTERNOON AND THE AFTERNOON AS A WAVE OF LOW PRESSURE PASSES OVERHEAD...HOWEVER WITH DRY CONDITIONS OVER THE PAST FEW DAYS...MOST LOCATIONS CAN HANDLE SOME RAINFALL AND THEREFORE EXPECT ANY FLOODING TO BE MINOR AND ISOLATED. A SECOND WAVE OF LOW PRESSURE WILL PASS ACROSS THE AREA LATE THIS EVENING...TRIGGERING ANOTHER ROUND OF RAIN ACROSS THE AREA. THE LOW WILL ALSO DRAG A COLD FRONT ACROSS THE CENTRAL APPALACHIANS WHICH WILL SHIFT OUR WINDS MORE FROM THE NORTH BY SUNRISE SUNDAY. WIDESPREAD LOW CLOUDS AND RAIN WILL KEEP TEMPERATURES ON THE MILD SIDE FOR OVERNIGHT LOWS...RANGING FROM THE LOW 50S ACROSS NORTHERN NORTH CAROLINA...TO THE UPPER 30S NEAR THE INTERSTATE 64 CORRIDOR.
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... AS OF 400 AM EDT SATURDAY... STRONG SHORT WAVE OF SATURDAY WILL SLIDE EAST-SOUTHEAST ACROSS THE VA/NC PIEDMONT TOWARD THE VA/NC COASTLINE SUNDAY AS THE DEEP UPPER LOW ACROSS THE CANADIAN MARITIMES SINKS SLOWLY SOUTHWARD. WEAK SFC LOW PRESSURE WILL RIDE ALONG THE BOUNDARY AS HIGH PRESSURE BUILDS SOUTHWARD FROM THE CENTRAL CANADIAN PROVINCES INTO THE REGION. MOIST...COOL...NORTHEAST MARITIME FLOW WILL CONTINUE ACROSS THE REGION...ESSENTIALLY CONTINUING THE COOL/WEDGE AIR MASS OF SAT. THUS...SUNDAY SHOULD BE A DREARY...UNSEASONABLY COOL DAY YET AGAIN WITH LIGHT RAIN THROUGHOUT THE DAY...BUT MOST LIKELY DURING THE FIRST HALF AS BY EVENING DRIER AIR SHOULD BEGIN TO WORK INTO THE REGION FROM THE NORTHWEST. RAINFALL AMOUNTS SUNDAY WILL GENERALLY BE 1/4 INCH OR LESS...FOCUSED MAINLY ACROSS THE EASTERN AREAS. FOR MONDAY...THE AFOREMENTIONED DEEP LOW WILL CONTINUE TO SAG SLOWLY SOUTHWARD TO OFF THE NEW ENGLAND COAST . DEEP NORTHERLY FLOW ALOFT WILL EVOLVE ACROSS THE REGION...ALLOWING COOL AIR TO CONTINUE TO FILTER INTO THE REGION FROM THE NORTH. A SHORT WAVE EMBEDDED WITHIN THE UPPER LOW ACROSS THE GREAT LAKES WILL MOVE TOWARD THE REGION DURING THE DAY. THIS WILL PROMOTE AN INCREASE IN -SHRA ACTIVITY...ESPECIALLY IN THE WEST AND NORTH. ACROSS THE HIGHER ELEVATIONS OF THE WESTERN MOUNTAINS...WITH 850MB TEMPS NEAR 0C...COULD NOT TOTALLY RULE OUT A FEW -SHSN...ESPECIALLY AT ELEVATIONS ABOVE 3500 FT...BUT NOT ENOUGH CONFIDENCE TO ADVERTISE IN THE GRIDS AT THIS POINT AND AT ANY RATE IT WOULD NOT CAUSE ANY PROBLEMS. THE ASSOCIATED CLOUD COVER AND PRECIPITATION WILL CONTINUE TO HOLD TEMPERATURES WELL BELOW NORMAL ONCE AGAIN MONDAY...ALTHOUGH PIEDMONT AREAS SHOULD BE SOMEWHAT WARMER THAN OVER THE WEEKEND WITH INCREASINGLY DOWNSLOPE NORTHWEST FLOW AND AS A RESULT FEWER CLOUDS. FOR TUESDAY...THE UPPER LOW SHIFTS FURTHER SOUTHEAST LEAVING THE AREA IN A WEAK COL AREA ON THE BACK SIDE OF THE DEPARTING LOW AND A CLOSED LOW IN THE SOUTHERN STREAM TRACKING EASTWARD FROM THE CENTRAL PLAINS. AT THIS POINT...TUESDAY APPEARS TO BE THE BEST DAY OF THE PERIOD WITH DRIER NORTHWEST FLOW AND LARGE SCALE SUBSIDENCE ON THE BACK SIDE OF THE NORTHERN ATLANTIC UPPER LOW. TEMPERATURES WILL AVERAGE A GOOD 10 DEGREES BELOW NORMAL THROUGHOUT THE PERIOD...WITH CLOUDS AND PRECIPITATION SUN- MON...AND A LARGE POCKET OF 850MB TEMPS HOVERING NEAR 0C THROUGHOUT THE PERIOD ON THE BACK SIDE OF THE NORTHERN ATLANTIC UPPER LOW. EXPECT HIGHS 50S MOUNTAINS TO 60S PIEDMONT AND LOWS 30S MOUNTAINS TO 40S PIEDMONT. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 415 AM EDT SATURDAY... MORE WET COOL WEATHER APPEARS LIKELY THROUGH THE PERIOD. MODELS CONTINUE TO DISAGREE ON THE DETAILS REGARDING THE ABSORPTION OF A SOUTHERN STREAM LOW TRACKING EASTWARD FROM THE CENTRAL PLAINS INTO THE PREDOMINANT NORTHERN STREAM/NW FLOW ACROSS THE EASTERN U.S. HOWEVER...GENERAL CONSENSUS IS THAT WE ARE IN FOR MORE RAIN AND BELOW NORMAL TEMPERATURES AS THE FAVORED TRACK OF THIS SYSTEM BY MOST MODELS IS NEAR OR JUST TO THE SOUTH OF OUR CWA. THE ECMWF REMAINS THE STRONGEST FOR THE SECOND CONSECUTIVE DAY WITH DEVELOPMENT OF A COASTAL LOW. ALL MODELS KEEP SFC LOW PRESSURE S-SE OF THE REGION...PUTTING US ON THE COLD SIDE OF THIS SYSTEM...WITH MODEST INFLUX OF ATLANTIC MOISTURE. HOWEVER...PWATS REMAIN MOSTLY LESS THAN 1 INCH WITH NO SIGNIFICANT INFLUX OF GULF MOISTURE UNDER THE PREVAILING NW FLOW ALOFT. THIS SHOULD KEEP RAIN AMOUNTS MODEST AND REDUCE FLOODING CONCERNS. THE HEAVIER RAINFALL SHOULD REMAIN WELL S-SE OF THE CWA DURING THE TIME FRAME. DRIER CONDITIONS SHOULD FINALLY RETURN BY FRIDAY AND MAY FINALLY CONTINUE FOR SOMETIME THEREAFTER AS AN UPPER RIDGE BUILDS EASTWARD FROM THE CENTRAL U.S. TEMPERATURES ARE EXPECTED TO CONTINUE BELOW NORMAL THROUGH THURSDAY...CREEPING A LITTLE CLOSER TO NORMAL FRIDAY. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... AS OF 215 AM EDT SATURDAY... SATELLITE IMAGERY INDICATES HIGH CLOUDS OVERSPREADING THE AREA THIS MORNING...WITH MID LEVEL CLOUDS MOVING IN FROM THE WEST. RADAR ALSO INDICATING SPOTTY SHOWERS APPROACHING FROM KENTUCKY... WHICH WILL HELP TO MOISTEN THE LOW LEVELS OF THE ATMOSPHERE AS THEY PASS ACROSS THE MOUNTAINS AFTER 2 AM. LOW LEVELS REMAIN DRY ENOUGH THIS MORNING THAT GENERALLY VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGH AROUND NOON...BEFORE CEILINGS QUICKLY DROP TO LOW MVFR/IFR DURING EARLY AFTERNOON FOR MUCH OF THE FORECAST REGION. THE FIRST OF TWO MAIN WAVES OF LOW PRESSURE WILL PASS ACROSS THE CENTRAL APPALACHIANS DURING LATE MORNING THROUGH MID AFTERNOON... BRINGING WIDESPREAD BUT LIGHT RAINFALL...IN ADDITION TO THE LOW CEILINGS. ONLY CONCERN FOR THUNDER WILL BE ACROSS FAR WESTERN VIRGINIA AND THE HIGHLANDS OF NORTH CAROLINA...WHERE WEDGING IS WEAKEST AND ISOLATED ACTIVITY IS POSSIBLE. RAINFALL WILL BECOME MORE SCATTERED BY EARLY EVENING AS MORE SUBTLE DISTURBANCES PASS OVERHEAD...BUT WITH HIGH PRESSURE OFF THE COAST MAINTAINING EASTERLY UPSLOPE WINDFLOW ACROSS THE CENTRAL APPALACHIANS... BELIEVE CEILINGS WILL BE PREDOMINANTLY IFR BY LATE AFTERNOON INTO THE OVERNIGHT AREAWIDE. SECOND WAVE OF LOW PRESSURE WILL FOLLOW SIMILAR PATH AS THE FIRST...PASSING ACROSS LATE TONIGHT AND EARLY SUNDAY. EXPECT RAIN TO ONCE AGAIN BECOME WIDESPREAD AFTER MIDNIGHT...PERSISTING THROUGH THE LATE MORNING HOURS OF SUNDAY. SECOND WAVE WILL DRAG A COLD FRONT ACROSS THE AREA...RESULTING IN A NORTHWESTERLY WIND SHIFT THAT WILL LEAD TO DRYING CONDITIONS AND DECREASING CLOUDS LATE SUNDAY AFTERNOON. EXTENDED AVIATION DISCUSSION... FLYING CONDITIONS WILL CONTINUE TO IMPROVE SUNDAY EVENING AS THE LOW PULLS FARTHER OFFSHORE AND WEAK HIGH PRESSURE BUILDS IN FROM THE NORTHWEST...WITH MOST LOCATIONS BACK TO VFR BEFORE MIDNIGHT MONDAY. BREEZY NORTHWEST FLOW IS EXPECTED FOR MONDAY AND EARLY TUESDAY WITH HIGH PRESSURE BUILDING IN FROM THE NORTHWEST...SO VFR CONTINUES. BY WEDNESDAY A SOUTHERN STREAM SYSTEM APPEARS TO MAINLY AFFECT THE GULF COAST REGION TO THE CAROLINAS...BUT COULD SEE RAIN AND/OR SUB VFR CEILINGS INTO THE DAN-BCB-BLF AREA...BUT CONFIDENCE IS LOW AT THIS TIME. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...NF NEAR TERM...MBS/NF SHORT TERM...RAB LONG TERM...MBS/RAB AVIATION...DS/NF/RAB

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