Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 020721 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 321 AM EDT WED SEP 2 2015 .SYNOPSIS... 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. && .NEAR TERM /THROUGH TONIGHT/... AS OF 240 AM EDT WEDNESDAY... OVERALL HOT AND HUMID WEATHER FOR EARLY SEPTEMBER TO PERSIST TODAY AS SURFACE HIGH PRESSURE REMAINS IN PLACE ACROSS THE MOUNTAINS. HOWEVER SHORTWAVE ENERGY IN THE FORM OF AN OPENING UPPER LOW ACROSS THE OHIO VALLEY WILL RIDE SOUTHEAST THROUGH THE 5H RIDGE AND OVER THE NORTHERN HALF OF THE AREA THIS AFTERNOON. THIS SHOULD RESULT IN BETTER LIFT ESPCLY ALONG AND JUST SOUTH OF THE INTERSTATE 64 CORRIDOR EARLY ON AND ACROSS THE EASTERN HALF THROUGH LATE IN THE DAY. LATEST GUIDANCE ALSO SHOWING BETTER INSTABILITY WITH A LITTLE MORE COOLING ALOFT...BUT STILL UNCERTAINTY WITH COVERAGE GIVEN OVERALL BROAD SUBSIDENCE IN PLACE UNDER RATHER WARM 5H TEMPS. CURRENT SPC/RNK WRF SOLUTIONS ALONG WITH THE LATEST HRRR REMAIN THE MOST WIDESPREAD WITH SHRA/TSRA NORTH HALF AND ALONG THE BLUE RIDGE. THIS WHILE MOST OTHER SOLUTIONS INCLUDING ENSEMBLES PRODUCING LESS INCLUDING ONLY WIDELY SCATTERED SHALLOW CONVECTION MAINLY CONFINED FROM THE VIRGINIA HIGHLANDS EAST TO AROUND KLYH FOR THE MOST PART. THEREFORE ALIGNED HIGHEST CHANCE POPS ACROSS THE FAR NORTH WITH A PERIOD OF LOWER CHANCES SOUTH/EAST DURING MID/LATE AFTERNOON AND ONLY ISOLATED COVERAGE FAR SW. GIVEN WEAK FLOW ALOFT NOT EXPECTING MUCH OF A SEVERE THREAT BUT COULD SEE A BIT MORE CLUSTERING OF SLOW MOVING CONVECTION RIGHT NEAR THE CORE OF THE UPPER WAVE LATE. OTHERWISE LOOKING AT MAINLY PC WITH MID DECK EARLY...THEN MORE CU THIS AFTERNOON WITH HIGHS AGAIN REACHING THE LOW 90S EAST AND WELL INTO THE 80S ELSEWHERE PENDING TIMING OF CONVECTIVE INITIATION. IMPULSE PASSES THIS EVENING LEAVING THE REGION IN BETWEEN WAVES AND UNDER SURFACE HIGH PRESSURE. THIS SHOULD ALLOW MOST CONVECTION TO FADE BY MIDNIGHT GIVEN LOSS OF HEATING AND SOME OVERNIGHT CLEARING PER WEAK NW FLOW ALOFT IN THE WAKE OF THE MID LEVEL SYSTEM. THUS KEEPING SOME LOW END CHANCE POPS GOING MAINLY EAST THIS EVENING BEFORE TRENDING DRY WITH FOG AGAIN OVERNIGHT. LOWS PERHAPS SLIGHTLY COOLER GIVEN SOME DROP IN DEWPOINTS AND ESPCLY WHERE ANY COOLING EVENING RAINFALL OCCURS BUT STILL MOSTLY LOW/MID 60S MOUNTAINS TO UPPER 60S EAST. && .SHORT TERM /THURSDAY 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 /07Z WEDNESDAY THROUGH SUNDAY/... 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. && .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...JH SHORT TERM...AMS LONG TERM...AMS AVIATION...JH/NF/WP EQUIPMENT...

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