Area Forecast Discussion
Issued by NWS Blacksburg, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KRNK 021340 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 940 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 930 AM EDT WEDNESDAY... EARLY MORNING FOG HAS DISSIPATED IN ALL BUT PARTS OF THE GREENBRIER AND NEW RIVER VALLEY REGIONS. HOWEVER...BY 1100 AM...AT VAST MAJORITY...IF NOT ALL...OF THIS FOG WILL HAVE DISSIPATED AS WELL. PRECIPITATION COVERAGE ACROSS THE REGION CURRENTLY IS ZERO. THERE WERE A FEW ISOLATED SHOWERS OVER BUCKINGHAM COUNTY AROUND THE TOP THE HOUR..BUT THESE HAVE SINCE FADED. LATEST MESOSCALE MODELS PAINTS VERY LITTLE IF ANY PRECIPITATION ACROSS THE NORTHERN PARTS OF THE AREA THROUGH 17Z/1PM...AND THEN START RAMPING UP THE COVERAGE AFTER THAT TIME. HAVE TWEAKED THE PROBABILITY OF PRECIPITATION GRIDS AND THE WEATHER GRIDS TO BETTER REFLECT THIS TREND. NO OTHER NOTABLE CHANGES AT THIS TIME. 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 SATURDAY NIGHT/... AS OF 415 AM EDT WEDNESDAY... WEAK UPPER-LEVEL SHORT WAVE WILL BE DISSIPATING ACROSS NORTH CAROLINA DRIFTING SLOWLY INTO THE SOUTHEAST STATES WHERE IT APPEARS IT IS DESTINED TO BECOME A WEAK CUTOFF THAT WILL RETROGRADE/LINGER ACROSS THE SOUTHEAST/MID-SOUTH INTO NEXT WEEK AS A LARGE HIGH AMPLITUDE UPPER RIDGE CONTINUES TO BUILD FROM THE SOUTH CENTRAL/CENTRAL U.S. INTO SOUTHEAST CANADA AND THE NORTHEAST U.S. OVER THE TOP OF THE WEAK CUTOFF LOW. UPPER SUPPORT WILL BE MINIMAL AT BEST WITH BEST DYNAMICS...WHAT THEY ARE...HAVING DRIFTED SOUTH OF THE AREA. ANY CONVECTION WILL LARGELY BE THE RESULT OF DIFFERENTIAL HEATING AND FOCUSED PRIMARILY ACROSS THE WESTERN MOUNTAINS. REALLY CANNOT SUPPORT MUCH MORE THAN 30 POPS AT BEST. BY FRIDAY...A LARGE SURFACE HIGH DEVELOPING ACROSS THE NORTHEAST U.S. UNDERNEATH THE MAMMOTH UPPER RIDGE WILL BEGIN TO PUSH A BACKDOOR FRONT FROM THE MID-ATLANTIC SOUTHWESTWARD. UPPER DYNAMICS ARE VERY WEAK...BUT A MARKED DEWPOINT GRADIENT WILL EXIST ALONG THE SOUTHWESTWARD ADVANCING BOUNDARY AS VERY DRY AIR ADVECTS SOUTHWEST INTO NORTHERN VA. THIS SHOULD BE SUFFICIENT TO SUPPORT ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS...WITH THE BEST COVERAGE SHIFTING SOUTHWEST TOWARD EVENING. INSTABILITY IS QUITE NOTABLE ACROSS THE REGION IN ADVANCE OF THIS BACKDOOR FRONT...SO EVEN WITH WEAK DYNAMICS...WITH THE NOTED INSTABILITY AND PWATS IN THE 1.5 TO 1.7 INCH RANGE...30-40 PERCENT POPS SEEMS REASONABLE. FOR SATURDAY...THE BACKDOOR FRONT CONTINUES TO DRIFT SOUTHWEST AND SHOULD BE LOCATED FROM CENTRAL WV THROUGH SOUTHWEST VA...NEAR THE I-77 CORRIDOR...INTO CENTRAL NC. VERY DRY AIR IS NOTED ADVECTING INTO THE REGION FROM THE NORTHEAST WITH DEWPOINTS DROPPING INTO THE 50S AND PWATS FALLING TO NEAR 0.50 INCH ACROSS THE NORTHEAST PART OF THE CWA. ANY CONVECTION SATURDAY SHOULD BE LIMITED TO THE I-77 CORRIDOR AND POINTS WESTWARD...PRIMARILY DURING THE AFTERNOON/EVENING. TEMPERATURES WILL REMAIN WELL ABOVE NORMAL THURSDAY AND FRIDAY AHEAD OF THE BACKDOOR FRONT...WITH MAX TEMPS WELL INTO THE 80S...NEAR 90 ACROSS THE PIEDMONT. MIN TEMPS WILL HOLD MOSTLY IN THE 60S TO EVEN NEAR 70 ACROSS THE PIEDMONT. THESE READINGS ARE AROUND 5 AND 10 DEGREES ABOVE NORMAL...RESPECTIVELY. MOS GUIDANCE HAS BEEN TRENDING TOO MUCH TOWARD CLIMATOLOGY...SO NEEDED TO NUDGE UP MOST AREAS FROM 2-3 DEGREES TO BETTER MATCH WHAT HAS BEEN OCCURRING RECENTLY. && .LONG TERM /SUNDAY THROUGH TUESDAY/... AS OF 445 AM EDT WEDNESDAY... THE FOCUS THROUGH THE PERIOD WILL BE ON THE AFOREMENTIONED WEAK AND INCREASING BROAD UPPER LOW ANCHORED ACROSS THE SOUTHEAST/MID- SOUTH PART OF THE U.S. OUR CWA WILL BE STUCK IN THE TRANSITION ZONE BETWEEN THIS INCREASINGLY MOIST/UNSTABLE AIR MASS TO THE SOUTH AND THE PERSISTING UPPER RIDGE AND ASSOCIATED SUBSIDENCE/VERY DRY AND WARM AIR MASS ACROSS THE MID-ATLANTIC REGION. SHOWER/THUNDERSTORM CHANCES WILL GRADUALLY CREEP NORTHWARD THROUGH THE PERIOD...BUT LIKELY REMAIN CONFINED TO AREAS WEST OF I-77 SUNDAY...THEN CREEP FURTHER NORTH TOWARD THE U.S. 460 CORRIDOR BY MONDAY AND MUCH OF THE CWA BY TUESDAY. THE BEST CHANCES THROUGHOUT THE PERIOD WILL REMAIN ACROSS THE WESTERN NC MOUNTAINS. THE MODELS HAVE CONTINUALLY DELAYED THE ARRIVAL OF A FRONT TOWARD THE MID PART OF NEXT WEEK...AND WITH THE UPPER RIDGE SANDWICHED IN BETWEEN THE LOW PRESSURE AREA TO THE SOUTH AND THE STRONGER WESTERLIES ALONG THE CANADIAN BORDER...IT MAY BE SOME TIME BEFORE IT ACTUALLY REACHES OUR AREA. HENCE...SUMMER APPEARS DESTINED TO HANG ON MUCH OF NEXT WEEK. MAX TEMPS SHOULD BE NEAR NORMAL AT THE BEGINNING OF THE PERIOD...BUT PERHAPS STILL SLIGHTLY ABOVE NORMAL WEST OF I-77. MIN TEMPS WILL REMAIN NEAR NORMAL TO SLIGHTLY ABOVE NORMAL FAR SOUTHWEST. MAX AND MIN TEMPS WILL CREEP TO SLIGHTLY ABOVE NORMAL LEVELS AGAIN AS WE MOVE INTO EARLY NEXT WEEK. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... AS OF 640 AM EDT WEDNESDAY... FOG AND STRATUS REMAIN SPOTTY ACROSS THE REGION EARLY THIS MORNING WITH THE TYPICAL VALLEY LOCATIONS SUCH AS KLWB/KBCB SEEING IFR OR WORSE ATTM. EXPECT COULD SEE A BRIEF REDUCTION IN VSBY AS WELL AROUND KLYH/KDAN AS WELL DURING THE NEXT HOUR OR TWO BEFORE HEATING HELPS DISSIPATE ANY RESIDUAL LOW LEVEL MOISTURE. OTHERWISE WAVES OF MID/HIGH CLOUDS AHEAD OF THE UPPER SYSTEM TO THE NW THE MAIN ASPECT ONCE ANY LOW CLOUDS BURN OFF WITH VFR EXPECTED AT ALL LOCATIONS FROM MID MORNING ONWARD. UPPER WAVE OVER THE OHIO VALLEY WILL SHIFT SLOWLY SOUTHEAST INTO VIRGINIA THIS AFTERNOON WHILE SLOWLY WEAKENING. THIS WILL ALLOW MORE INSTABILITY WITH STEEPER LAPSE RATES AND LIFT. SHOWERS AND STORMS WILL BE MORE SCATTERED THIS AFTERNOON WITH BEST FORCING ACROSS THE NORTHERN FOOTHILLS/PIEDMONT TO THE NEW RIVER VALLEY. AS OF NOW WILL KEEP THE GOING VCTS AT KROA/KLYH AND KBCB AFTER 19-20ZZ/3-4PM...BUT THINK COVERAGE WILL BE LESS FURTHER WEST AND OVER THE SOUTHEAST...SO ONLY GOING WITH A VCSH AT KLWB-KBLF WHILE KEEPING MENTION OUT OF KDAN FOR NOW. OVERALL EXPECT VFR CONDITIONS OUTSIDE ANY CONVECTION INTO THIS EVENING 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. A WEAK BACKDOOR COOL FRONT MAY ENHANCE THE CHANCES FOR SHOWERS AND STORMS LATER FRIDAY BEFORE DRIER AIR ARRIVES FRIDAY NIGHT. FOR SATURDAY 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 AT LEAST TO START THE WEEKEND. && .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...DS/JH SHORT TERM...RAB LONG TERM...AMS/RAB AVIATION...JH/NF/WP EQUIPMENT...

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.