Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 311105 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 705 AM EDT SUN MAY 31 2015 .SYNOPSIS... HIGH PRESSURE OFFSHORE WILL MAINTAIN A WARM AND HUMID AIRMASS ACROSS THE REGION TODAY. A COLD FRONT WILL APPROACH FROM THE NORTHWEST BY TONIGHT...BEFORE DRIFTING INTO THE REGION AND STALLING EARLY NEXT WEEK...RESULTING IN AN INCREASING THREAT FOR SHOWERS AND THUNDERSTORMS LATER TODAY INTO TUESDAY. THE FRONT MAY FINALLY SLIDE SOUTH OF THE REGION BY WEDNESDAY BRINGING SOMEWHAT COOLER AIR FOR THE END OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... AS OF 225 AM EDT SUNDAY... UPPER RIDGING ACROSS MUCH OF THE REGION WILL BEGIN TO SLOWLY BREAKDOWN TODAY AS WEAK 5H TROFFINESS DRIFTS EASTWARD PUSHING ITS ASSOCIATED SURFACE COLD FRONT TO JUST WEST OF THE MOUNTAINS BY THIS EVENING. INCREASING MOISTURE AHEAD OF THESE FEATURES SHOULD INTERACT WITH STRONG HEATING TO RESULT IN A BIT BETTER COVERAGE OF SHOWERS/STORMS ESPCLY MOUNTAINS THIS AFTERNOON WHERE SOME SLIGHT COOLING ALOFT WILL TAKE PLACE. PREDOMINATE SW FLOW AHEAD OF THE FRONT LOOKS TO HELP INITIATE CONVECTION ALONG THE BLUE RIDGE EARLY ON WHERE MAY BE AIDED VIA DIFFERENTIAL HEATING GIVEN EARLY CLOUDS AND WEAK FLOW. LIFT JUST AHEAD OF THE APPROACHING BOUNDARY SHOULD FINALLY CATCH UP WITH ONGOING SHRA/TSRA OVER THE WEST LATE AS SEEN PER LATEST NCAR ENSEMBLE AND NAM SOLUTIONS. APPEARS MAY JUST SEE ENOUGH RESIDUAL RIDGING TO LIMIT EASTWARD PUSH/DEVELOPMENT ALTHOUGH IF THINGS ORGANIZE MORE THEN POTENTIAL FOR SOME COVERAGE TO DRIFT EAST OF THE BLUE RIDGE ESPCLY LATE. THUS CONTINUING WITH A PERIOD OF LIKELY POPS SOUTHERN BLUE RIDGE AND POINTS WEST THIS AFTERNOON...WITH CHANCES EAST OUT TO AROUND HIGHWAY 29...BUT ONLY ISOLATED FARTHER EAST. AGAIN APPEARS HEAVY RAIN THE MAIN THREAT GIVEN SLOW MOVEMENT ALTHOUGH PERHAPS MORE BANDS/CLUSTERS COULD SUPPORT AN ISOLATED PULSE SEVERE WIND THREAT ESPCLY NORTH WHERE LAPSES ARE BETTER DESPITE WEAK WINDS ALOFT. WILL KEEP HIGH TEMPS SIMILAR TO BEFORE WITH MOSTLY LOW/MID 80S PENDING EARLY CLOUDS...AND HOW FAST CONVECTION DEVELOPS WHICH COULD LIMIT HIGHS IN SPOTS. WEAK WAVE PROGGED TO DEVELOP ALONG THE FRONT ACROSS THE WESTERN SLOPES THIS EVENING BEFORE LIFTING TO THE NORTH OVERNIGHT. SHOULD HAVE SOME ONGOING SCATTERED CONVECTION EARLY THIS EVENING MAINLY WESTERN HALF BEFORE LOSS OF HEATING AND EXITING LIFT ALLOW FOR A BRIEF TAPERING OFF TREND BY MIDNIGHT. THIS BEFORE CONVERGENCE STARTS TO RETURN TOWARD MORNING WEST AHEAD OF THE NEXT IMPULSE TO THE SW. HOWEVER PLENTIFUL MOISTURE AND WEAK DIFFLUENCE ALOFT WOULD SUPPORT THE NEED FOR CHANCE POPS MUCH OF THE NIGHT MOUNTAINS SO KEPT SOME POPS LINGERING BUT ONLY ISOLATED IN THE EAST ESPCLY AFTER MIDNIGHT. OTRW PARTLY TO MOSTLY CLOUDY WITH SOME PATCHY FOG AND LOWS AGAIN MOSTLY 60S GIVEN MOISTURE AROUND. && .SHORT TERM /MONDAY THROUGH WEDNESDAY/... AS OF 245 AM EDT SUNDAY MEDIUM RANGE MODELS AND ENSEMBLES CONTINUE THE TREND OF SLOWING THE EASTERN PROGRESSION OF A SFC COLD FRONT...AND CUTTING OFF AN UPPER LOW IN THE SOUTHEAST U.S. THROUGH THE SHORT TERM PERIOD. IN TERMS OF SENSIBLE WEATHER THIS MEANS A WETTER AND WARMER PERIOD THAN EARLIER FORECAST. EXPECT NUMEROUS SHOWERS AND STORMS ON MONDAY...AS UPPER LEVEL DIVERGENCE INCREASES IN RESPONSE TO THE DIGGING UPPER LEVEL LOW IN THE SOUTHERN U.S. IN ADDITION...MUCH HIGHER PWAT AIR SURGES INTO THE REGION. INSTABILITY SHOULD BE LESS COMPARED TO THIS PAST WEEKEND...BUT IS EXPECTED TO BE HIGHEST IN THE EAST WHERE CLOUD COVER SHOULD BE LESS. ISOLATED SEVERE STORMS AND LOCALLY HEAVY RAINS WILL BE POSSIBLE AND WILL CONTINUE TO HIGHLIGHT THIS THREAT IN THE HWO. WHILE 850MB THERMAL RIDGE WILL SIT OVER OUR REGION...ABUNDANT CLOUD COVER SHOULD KEEP TEMPS A FEW DEGREES COOLER IN THE WEST COMPARED TO SUNDAY. A PRE-FRONTAL BOUNDARY...ASSOCIATED WITH A NORTHERN STREAM WAVE MOVING INTO NEW ENGLAND...MOVES INTO OUR FORECAST AREA TUESDAY...BUT TRUE SFC BOUNDARY WITH LOWER DEW POINTS REMAINS TO OUR WEST ON TUESDAY. PWAT VALUES 1-2 STANDARD DEVIATIONS ABOVE NORMAL REMAIN IN PLACE ALONG WITH CONTINUES UPPER DIVERGENCE ON THE NORTHEAST SIDE OF THE SOUTHERN U.S. UPPER LEVEL LOW. THIS SPELLS FOR A MUCH WETTER DAY THAN EARLIER FORECAST...AND PUSHED UP POPS TO HIGH CHANCE ACROSS THE FORECAST AREA. DEPENDING ON INSTABILITY...ISOLATED SEVERE STORMS AND LOCALLY HEAVY RAINS AGAIN ARE POSSIBLE.CLOUDS WILL AGAIN KEEP TEMPS TOWARD THE COOLER SIDE OF GUIDANCE...BUT MUGGY CONDITIONS WILL CONTINUE. COLD FRONTAL PASSAGE IS NOW EXPECTED TO ARRIVE WEDNESDAY...BUT WITH TRENDS BEING SLOWER...WENT ABOVE GUIDANCE FOR HIGHS IN THE SOUTH AND INCREASES POPS ESPECIALLY IN THE SOUTHERN PORTION OF THE FORECAST AREA WHERE BEST FORCING IS FORECAST. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... AS OF 330 PM EDT SATURDAY... HIGH PRESSURE WILL REMAIN WEDGED AGAINST THE APPALACHIANS THROUGH THE LATER HALF OF THE COMING WORKWEEK...MAINTAINING AN EAST TO SOUTHEASTERLY WIND FLOW ACROSS OUR AREA. WITH AN UPPER LEVEL LOW SPINNING ACROSS THE LOWER MISSISSIPPI VALLEY...AND LIGHT SOUTHWESTERLY FLOW ALOFT PUSHING ALONG THE CENTRAL APPALACHIAN CHAIN...DO NOT SEE THE COLD FRONT SINKING VERY FAR AWAY FROM OUR AREA...PERHAPS STALLING ACROSS CENTRAL NORTH CAROLINA. AS SUCH... WILL MAINTAIN A CHANCE FOR SHOWERS AND THUNDERSTORMS EACH DAY ACROSS OUR AREA...WILL BETTER RAIN CHANCES ACROSS THE MOUNTAINS WEST OF INTERSTATE 77...AS WELL AS OVER THE NORTH CAROLINA PIEDMONT. INSTABILITY WILL BE MORE ON THE MARGINAL SIDE...SO BELIEVE THE POTENTIAL FOR ANY STRONG THUNDERSTORMS WILL BE LOW...BUT WITH PLENTY OF DEEP MOISTURE FLOWING NORTH ALONG THE APPALACHIAN CHAIN...WILL HAVE WATCH FOR AREAS OF LOCALLY HEAVY RAIN EACH AFTERNOON AND EVENING. EXPECT TEMPERATURES TO BE NEAR NORMAL FOR EARLY JUNE AREAWIDE. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/...
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AS OF 645 AM EDT SUNDAY... EXPANSIVE MID DECK CROSSING THE WESTERN MOUNTAINS CONTINUES TO HINDER FOG DEVELOPMENT EARLY THIS MORNING WITH ONLY A FEW SPOTS ACROSS THE VALLEYS SEEING ANY VSBY RESTRICTIONS. HOWEVER ISOLATED SHOWERS WITHIN THIS CORRIDOR OF MAINLY MID LEVEL CANOPY TO PERHAPS AFFECT KBLF IN THE NEXT HOUR OR TWO AND KLWB THROUGH MID OR LATE MORNING. MAY NEED TO INCLUDE A VCSH FOR THOSE LOCATIONS FOR A FEW HOURS THIS MORNING. OTHERWISE EXPECTING MAINLY VFR CIGS/VSBYS IN MID DECK OUTSIDE ANY LOCAL SHRA OR PATCHY VALLEY FOG. ONLY EXCEPTION MAY BE AT KDAN WHERE LOWER MVFR CIGS IN STRATO-CU COULD PUSH NORTH ACROSS THAT AREA THROUGH MID/LATE MORNING. SHOULD SEE THE AREAS OF MID/LOW CLOUDS SLOWLY ERODE WITH HEATING BY MIDDAY...GIVING WAY TO MORE OF A 4-6K FT CU FIELD FOR MUCH OF THE REGION AHEAD OF A COLD FRONT TO THE WEST THIS AFTERNOON. ONCE AGAIN HEATING OF THIS MOISTURE WILL HELP DEVELOP CONVECTION BETWEEN 16Z-18Z /NOON-2PM...WITH GREATEST THREAT IN THE MOUNTAINS AND FOOTHILLS. APPEARS ENOUGH COVERAGE TO WARRANT A PREVAILING PERIOD OF CONVECTION AT KBLF/KLWB THIS AFTERNOON WITH CONTINUED VCTS AT KBCB AND KROA...WHILE LEAVING OUT MENTION FURTHER EAST AT KLYH OR KDAN FOR NOW. SHOWERS MAY LINGER ALONG THE BLUE RIDGE AND POINTS WEST INTO THIS EVENING BEFORE CONVECTION FADES TO MORE ISOLATED COVERAGE IN PATCHY FOG/STRATUS AND MID DECK AFTER MIDNIGHT. THIS MAY PERIODS OF MVFR IN SHRA/TSRA TO WESTERN LOCATIONS EARLY THIS EVENING WITH MORE IN THE WAY OF MVFR/IFR IN FOG/STRATUS TO THE VALLEY LOCATIONS SUCH AS KLWB/KBCB LATE. SOME FOG AND LOW CLOUDS ALSO POSSIBLE WHERE SHOWERS OCCUR TODAY ESPCLY AROUND KBLF SO INCLUDED A LOWER VSBY THERE IN FOG LATE GIVEN A LIGHT WEST WIND. EXTENDED DISCUSSION... THE SLOWLY APPROACHING COLD FRONT IS EXPECTED TO SINK SOUTH INTO THE REGION ON MONDAY RESULTING IN EVEN HIGHER THREAT OF CONVECTIVE ACTIVITY...ESPECIALLY FROM THE BLUE RIDGE EAST...WITH THE THREAT PERSISTING INTO AT LEAST MONDAY NIGHT BEFORE THE BOUNDARY SINKS A LITTLE FURTHER SOUTH. THIS SHOULD MAKE FOR MORE FREQUENT PERIODS OF SUB- VFR INTO TUESDAY WITH LOWER CIGS/VSBY REDUCTIONS DUE TO SHOWERS/STORMS BY DAY...AND IN PATCHY FOG EARLY MORNING FOG. MODELS TRENDS IN STALLING THE FRONT NEAR THE REGION DURING MIDWEEK SUGGESTS LESS DRYING WITH CONTINUED ROUNDS OF SHOWERS AND POSSIBLE STORMS BOTH WEDNESDAY INTO THURSDAY...WITH PERHAPS LINGERING MVFR/IFR CONDITIONS AS WELL DUE TO THE COMBINATION OF EASTERLY FLOW AND PERIODS OF SHOWERS.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...PH LONG TERM...NF AVIATION...AMS/JH/WERT

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