Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 251755 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 155 PM 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/... 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. && .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 /18Z SATURDAY THROUGH THURSDAY/... AS OF 1215 PM EDT SATURDAY... WARM FRONT REMAINS DRAPED ACROSS THE AREA EXTENDING FROM A LOW PRESSURE SYSTEM OVER THE MID MISSISSIPPI VALLEY...WITH SHOWERS FLOWING EASTWARD ALONG THE FRONT. LOW LEVELS OF THE ATMOSPHERE HAVE BEEN SLOWER TO SATURATE THAN GUIDANCE WOULD INDICATE AND BELIEVE THIS TREND WILL CONTINUE...ESPECIALLY WITH PRECIPITATION A BIT MORE SPARSE THAN EXPECTED. HOWEVER...STILL EXPECT IFR CIGS TO BECOME ESTABLISHED ALONG WITH SOME DRIZZLE THIS EVENING AND THEN PERSIST INTO SUNDAY. GUIDANCE IS STILL LIKING THE IDEA OF DEVELOPING CONVECTIVE ACTIVITY UPSTREAM AND MOVING IT INTO THE AREA EARLY TONIGHT AND BELIEVE THIS IS A PLAUSIBLE SCENARIO WITH THE ACTIVITY WEAKENING AS IT ENCOUNTERS THE MORE STABLE AIR ENTRENCHED ACROSS THE AREA. TRACK OF EXPECTED PRECIPITATION WILL MAINLY AFFECT KBLF/KBCB/KDAN AND WILL MENTION THUNDER AT KDAN DUE TO CLOSER PROXIMITY TO UNSTABLE AIR TO THE SOUTH. THE LOW WILL BE PULLING AWAY FROM THE REGION ON SUNDAY AND THIS SHOULD ALLOW FOR A GRADUAL IMPROVEMENT LATER IN THE TAF PERIOD. DO NOT EXPECT A LOT OF WIND THROUGH THE TAF PERIOD IN E/NE FLOW. KBLF MAY SEE A LOW GUST OR TWO AND THERE WINDS WILL BECOME SWLY OVERNIGHT. THEN EXPECT A TREND TO A NORTHERLY TO NWLY COMPONENT LATER IN THE TAF PERIOD ON THE BACKSIDE OF THE DEPARTING LOW. 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...MBS/RAB

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