Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 020512 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 112 AM EDT WED SEP 2 2015 .SYNOPSIS...
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A RIDGE OF HIGH PRESSURE WILL REMAIN OVER THE REGION THROUGH THE END OF THE WEEK. UPPER LEVEL DISTURBANCES TRACKING THROUGH THE RIDGING WILL RESULT IN WIDELY SCATTERED MAINLY DIURNAL SHOWERS AND STORMS INTO FRIDAY. A WEAK BACKDOOR COLD FRONT WILL DROP SOUTH THROUGH THE AREA BY THE END OF WEEK BRINGING SOMEWHAT DRIER AND COOLER AIR FOR THE WEEKEND.
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&& .NEAR TERM /THROUGH TODAY/... 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 /TONIGHT 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 /06Z WEDNESDAY THROUGH SUNDAY/...
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AS OF 100 AM EDT WEDNESDAY... OTHER THAN FOR DEBRIS MID/HIGH CLOUDS...FOG THE MAIN CONCERN OVERNIGHT WITH POTENTIAL AGAIN GIVEN LESS CLOUDS OF SEEING THE VALLEYS SUCH AS KLWB/KBCB DROP INTO LIFR/IFR FOR A PERIOD PRIOR TO DAYBREAK. ALSO SOME FOG POSSIBLE AROUND KLYH-KDAN WHERE BRIEF MVFR TO IFR POSSIBLE WHILE COVERAGE LOOKS QUITE SPOTTY AT KBLF WHERE LIMITED TO JUST A VERY BRIEF INCLUSION OF MVFR CONDITIONS AROUND DAWN. FOR WEDNESDAY...SHOULD SEE ANY LOW CLOUDS/FOG FADE WITH THE ONSET OF HEATING ALLOWING FOR VFR CONDITIONS TO QUICKLY RETURN BY MID MORNING IF NOT SOONER. THEN EXPECT THE UPPER WAVE OVER THE OHIO VALLEY TO SLOWLY SHIFT SOUTHEAST INTO VIRGINIA. THIS WILL ALLOW MORE INSTABILITY WITH STEEPER LAPSE RATES AND LIFT. SHOWERS AND STORMS WILL BE MORE SCATTERED WEDNESDAY AFTERNOON WITH BEST FORCING ACROSS THE FOOTHILLS/PIEDMONT TO THE NEW RIVER VALLEY. AS OF NOW WILL KEEP THE GOING VCTS AT KROA/KLYH AND KBCB AFTER 19Z/3PM...BUT THINK COVERAGE WILL BE LESS FURTHER WEST AND SOUTHEAST...SO ONLY GOING WITH A VCSH AT KLWB-KBLF WHILE KEEPING MENTION OUT OF KDAN. 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.
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&& .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...JH/NF NEAR TERM...NF/WP SHORT TERM...AMS LONG TERM...AMS AVIATION...JH/NF/WP EQUIPMENT...

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