Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 020352 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1152 PM EDT TUE SEP 1 2015 .SYNOPSIS... AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL STRENGTHEN OVER THE APPALACHIANS AND CENTRAL MID ATLANTIC REGION TODAY...KEEPING US IN A RATHER STAGNANT PATTERN WITH ISOLATED AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS THROUGH LATE IN THE WEEK. A WEAK BACKDOOR COLD FRONT WILL DROP SOUTH THROUGH THE AREA BY THE WEEKEND. && .NEAR TERM /THROUGH WEDNESDAY/... AS OF 1150 PM EDT TUESDAY... SHOWERS HAVE FADED AND SKIES WILL STAY CLEAR TO PARTLY CLOUDY SOUTH TO MORE CLOUDS IN THE NORTHERN CWA CLOSER TO THE UPPER SHORTWAVE. WILL MAINTAIN FOG LATE TONIGHT. NO OTHER SIGNIFICANT CHANGES TO THE FORECAST WERE MADE. PREVIOUS EARLY EVENING DISCUSSION... JUST A FEW SHOWERS OUT THERE EARLY THIS EVENING IN ASSOCIATION HIGHER THETA-E GRADIENT OVER THE PIEDMONT AND WV/FAR SW VA. BEST DEEP MOISTURE CONVERGENCE RESIDES IN THE PIEDMONT. WE HAVE WEAK IMPULSES STRETCHED ACROSS WV INTO VA...AIDING IN WEAK LIFT. OVERALL...NOT IMPRESSED WITH THREAT PAST 9PM...SO I EXPECT ANY SHOWERS TO FADE BEFORE MIDNIGHT. WILL BE DEALING WITH SOME HIGH CLOUDS THROUGH THE NIGHT...ESPECIALLY THE NRN CWA...WITH SCATTERED LOW/MID CLOUDS. MADE ONLY MINOR ADJUSTMENTS TO PREVIOUS FORECAST...WITH MOST OCCURRING WITH THE SKY COVER. WILL HAVE TO SEE IF THE OVERNIGHT SKY COVER CAN INFLUENCE FOG FORMATION. WILL LOOK AT THAT LATER THIS EVENING. PREVIOUS FORECAST DISCUSSION ISSUED MID AFTERNOON... STARTING SEPTEMBER OFF ON THE WARM SIDE WITH AFTERNOON TEMPERATURES RANGING FROM THE LOW 80S WEST TO THE LOW 90S OVER THE PIEDMONT. SLOW MOVING SHOWERS HAVE DEVELOP WITH AFTERNOON HEATING...BUT HAVE HELD NEAR THE INTERSTATE 64 CORRIDOR FOR THE MOST PART...WITH ONLY A FEW SPRINKLES ELSEWHERE ACROSS THE MOUNTAINS. WE CAN EXPECT THESE SHOWERS TO FADE TOWARD SUNSET AS HEATING ENDS...AND EXPECT CLOUDS TO FADE AS WELL...MAKING FOR PARTLY CLOUDY SKIES ENTERING THE NIGHT. WITH DEWPOINTS EXPECTED TO HOLD IN THE 60S OVERNIGHT...LIGHT WINDS AND ONLY SCATTERED CLOUDS...PATCHY FOG APPEARS LIKELY ONCE AGAIN ACROSS THE AREA...AT LEAST DURING THE EARLY HALF OF THE NIGHT. MID AND HIGH CLOUDS WILL BEGIN TO INCREASE SHORTLY BEFORE DAWN AS AN UPPER LEVEL DISTURBANCE APPROACHES FROM THE OHIO VALLEY...WHICH MAY CAUSE SOME OF THE FOG TO THIN BEFORE SUNRISE. OTHERWISE... EXPECT A MUGGY WARM NIGHT...WITH LOWS HOLDING IN THE LOW TO MID 60S AREAWIDE. ANY REMAINING FOG WILL BURN OFF QUICKLY AFTER 10 AM WEDNESDAY WITH ANOTHER DAY OF STRONG HEATING. THE UPPER LEVEL DISTURBANCE WILL DRIFT ACROSS THE NORTHERN HALF OF THE AREA DURING EARLY AFTERNOON... AND EXPECT GREATER COVERAGE OF SHOWER ACTIVITY ACROSS THE MOUNTAINS. FORECAST MODEL SOUNDINGS INDICATE THAT THERE WILL BE ENOUGH INSTABILITY PRESENT FOR A FEW OF THE SHOWERS TO INTENSIFY INTO THUNDERSTORMS DURING MID AFTERNOON. AS THE DISTURBANCE WILL BE SLOW MOVING...LINGER ACROSS OUR AREA THROUGH SUNSET. AFTERNOON HIGH TEMPERATURES WILL REACH THE UPPER 70S/LOW 80S ACROSS THE MOUNTAINS...AND CLIMB AS HIGH AS THE LOW 90S ACROSS THE SOUTHSIDE. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/... AS OF 345 PM EDT TUESDAY... THE GFS MOVES THE OHIO SHORT WAVE SLOWER THAN THE NAM/SREF. GIVEN THE LACK OF A KICKER FOR THIS VORT MAX...THE SLOWER GFS SEEMS MORE REASONABLE...BUT EVEN ON THIS SLOWER TRACK THE SHORT WAVE WILL STILL BE SOUTHEAST OF THE FORECAST AREA BY THURSDAY AFTERNOON. WILL EXTEND THE PROBABILITY OF PRECIPITATION IN THE FORECAST FOR WEDNESDAY NIGHT. STAYED CLOSER TO MAV GUIDANCE THROUGH THE PERIOD. BACKDOOR FRONT MOVES SOUTH THROUGH THE NEW ENGLAND AND MID ATLANTIC COAST. MODELS WERE SHOWING SOME CONVERGENCE IN EASTERN VIRGINIA BUT STILL QUESTIONABLE HOW MUCH LIFT THIS FEATURE MAY PROVIDE FOR THE COUNTY WARNING AREA. BEST PROBABILITY OF PRECIPITATION WILL BE IN THE NORTHEAST COUNTIES OF THE FORECAST AREA...EAST OF THE BLUE RIDGE. AS THIS FRONT MOVES DOWN THE COAST AND HIGH PRESSURE BUILDS SOUTH OVER THE APPALACHIANS...WINDS WILL TURN FROM NORTH TO EAST. THIS EASTERLY COMPONENT OF THE WIND AT THE SURFACE THROUGH LOW LEVELS MAY ALSO EXPAND THE CLOUD COVER AND PROBABILITY OF PRECIPITATION ALONG THE BLUE RIDGE. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... AS OF 100 PM EDT TUESDAY... LOWER 500 MB HEIGHTS REMAINED TRAPPED UNDER THE RIDGE OVER THE SOUTHEAST UNITED STATES FRIDAY NIGHT THROUGH SUNDAY. SUNDAY NIGHT INTO TUESDAY...THE CENTER OF THE UPPER RIDGE...DRIFTS SOUTH INTO THE MID ATLANTIC REGION. HEIGHTS WILL BE CLOSE TO 594DM ACCORDING TO THE 00Z GFS. AT THE SURFACE FRIDAY NIGHT ANY REMNANTS OF THE BACKDOOR FRONT WASH OUT AND BY SATURDAY THE WEDGE WILL BE FULLY ESTABLISHED AND THIS FEATURE WILL REMAIN IN PLACE THROUGH SUNDAY. HIGH PRESSURE WILL COVER THE MID ATLANTIC STATES THROUGH TUESDAY. UNSEASONABLY WARM TEMPERATURES...WITH 850 MB TEMPERATURES APPROACHING +20...MOVE INTO THE REGION WITH THE HIGHER HEIGHTS. A DRIER AIR MASS BEGINS TO APPROACH THE REGION AS THE WEDGE BUILDS IN ON SATURDAY. SUNDAY AND MONDAY...ECMWF WAS SHOWING MUCH DRIER AIR ABOVE 850MB. BELOW 850 MB THE DRIER AIR REMAINS EAST AND SOUTH OF THE FORECAST AREA THROUGH MONDAY. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... AS OF 730 PM EDT TUESDAY... HAVE VCSH AT ROA/LYH PER RADAR AT 2315Z. THINK ANY SHOWERS WILL FADE TOWARD 10 PM/02Z..THEN SKIES WILL STAY SCT-BKN OVERNIGHT. FORECAST SOUNDINGS FAVOR SOME FOG AT LWB/BCB...AND MORE TEMPO AT LYH/DAN. IFR/LIFR FOG AT LWB WILL STAY IN THE FORECAST...BUT IF THE CIRRUS OVERHEAD REMAINS THICK ENOUGH THEN IT WILL BE SHORT LIVED. FOR WEDNESDAY...EXPECT THE UPPER WAVE OVER THE INDIANA/OHIO BORDER THIS EVENING TO SLOWLY SHIFT INTO VIRGINIA. THIS WILL ALLOW MORE INSTABILITY WITH STEEPER LAPSE RATES AND LIFT. SHOWERS AND STORMS WILL BE MORE SCATTERED WED AFTERNOON WITH BEST FORCING ACROSS THE FOOTHILLS/PIEDMONT TO THE NEW RIVER VALLEY. AS OF NOW WILL ALLOW FOR VCTS AT ROA/LYH AND BCB AFTER 19Z...BUT THINK COVERAGE WILL BE LESS FURTHER WEST AND SOUTHEAST...SO LEFT IT OUT OF BLF/LWB AND DAN FOR NOW. OVERALL EXPECT VFR CONDITIONS WEDNESDAY WITH CIGS OF 4-6KFT WITH TCU AND CB IN THE AFTERNOON. EXTENDED AVIATION DISCUSSION... THE FORECAST AREA WILL REMAIN IN A WEAKLY FORCED SYNOPTIC ENVIRONMENT THROUGH THURSDAY...WITH CHANCES FOR DIURNAL CONVECTION MAINLY FROM THE BLUE RIDGE WEST...AND SOME MVFR/IFR FOG/STRATUS DEVELOPMENT AT NIGHT...ESPECIALLY AT KBCB AND KLWB. FOR FRIDAY INTO SUNDAY WILL SEE HIGH PRESSURE IN CONTROL THOUGH THE POSITION OF THE HIGH OVER THE MID ATLANTIC MAY SLIDE MORE MVFR CIGS OFF THE ATLANTIC INTO OUR EASTERN TAF LOCATIONS. && .EQUIPMENT... AS OF 400 PM EDT TUESDAY... THE DEW POINT READING AT KJFZ...RICHLANDS VA AWOS...IS INCORRECT. AT THIS TIME WE DO NOT KNOW WHEN THIS SENSOR WILL BE REPAIRED. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...NF NEAR TERM...NF/WP SHORT TERM...AMS LONG TERM...AMS AVIATION...NF/WP EQUIPMENT...

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