Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 311830 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 230 PM 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 /18Z SUNDAY THROUGH FRIDAY/... AS OF 220 PM EDT SUNDAY... HAVE FOUR MAIN SECTIONS OF THE TAFS DURING THIS FORECAST PERIOD. ALREADY HAVE SCATTERED THUNDERSTORMS IN THE REGION. WILL UPDATE AS NEEDED WHEN STORMS GET MUCH CLOSER TO APPROACHING A PARTICULAR AIRPORT...OTHERWISE COVERAGE IS INTO ORGANIZED ENOUGH TO INCLUDE ANYTHING BY VCTS/VCSH IN THE TAFS THROUGH 00Z/8PM. MOST LIKELY AIRPORTS TO HAVE SCATTERED THUNDERSTORMS AND THE ASSOCIATED MVFR VISIBILITY WITH HEAVY RAIN ARE KBCB AND KROA. WITH LOSS OF HEATING COVERAGE OF SHOWERS AND THUNDERSTORMS WILL DIMINISH ENOUGH TO LEAVE OUT OF THE TAFS OVERNIGHT. HOWEVER...THERE WILL HAVE BEEN ENOUGH RAIN THIS AFTERNOON FOR PATCHY FOG. EXPECT FOG ALONG THE NEW RIVER UPSTREAM OF KBCB AND ON THE GREENBRIER RIVER IF THERE IS ENOUGH CLEARING. HAVE ADDED LIFR FOG IN AT KLWB AND MVFR FOG IN FOR KBCB LATE TONIGHT. MODELS SHOWED KDAN AGAIN WITH AN MVFR CEILINGS EARLY MONDAY MORNING. EXTENDED DISCUSSION... THE SLOWLY APPROACHING COLD FRONT IS EXPECTED TO SINK SOUTH INTO THE REGION TONIGHT AND MONDAY RESULTING IN EVEN HIGHER THREAT OF CONVECTIVE ACTIVITY...ESPECIALLY FROM THE BLUE RIDGE WEST...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 INTO THURSDAY...WITH PERHAPS LINGERING MVFR/IFR CONDITIONS AS WELL DUE TO THE COMBINATION OF EASTERLY FLOW AND PERIODS OF SHOWERS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...PH LONG TERM...NF AVIATION...AMS/JH

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