Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 261141 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 741 AM EDT SAT JUL 26 2014 .SYNOPSIS... A WARM FRONT LIFTS NORTH ACROSS THE AREA TODAY WITH WINDS SHIFTING TO THE WEST. A COMPLEX OF THUNDERSTORMS WILL DEVELOP ALONG THIS FRONTAL BOUNDARY IN THE OHIO VALLEY BY EVENING AND SPREAD SOUTHEAST TOWARD OUR AREA BY SUNDAY. A STRONG COLD FRONT SHOULD MOVE ACROSS THE MID ATLANTIC AND SOUTHERN APPALACHIANS BY MONDAY...WITH COOLER WEATHER FOR THE MIDDLE OF NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 715 AM SATURDAY... UPDATED TO ALLOW FOR MORE CLEARING PER SAT LOOP AND WEB CAMS SHOWING MORE SUNSHINE. NO OTHER CHANGES WERE MADE WITH THIS UPDATE. AS OF 530 AM SATURDAY... UPDATED FORECAST THROUGH MID MORNING REFLECTS LIMITED PRECIP CHANCES...AND LESS SKY COVER TO THE WEST OF INTERSTATE 81. SHOWERS FADED AS THEY MOVED EAST TOWARD MARTINSVILLE. CANNOT RULE OUT A LONE SHOWER DEVELOPING IN THE HIGHER THETA-E AIR IN THE PIEDMONT THROUGH 8 AM...BUT OVERALL SHOULD BE DRY. AS OF 320 AM EDT SATURDAY... MODERATE TO HEAVY SHOWERS HAVE PLAGUED PATRICK COUNTY EARLY THIS MORNING PER WEAK SE FLOW AND HIGHER THETA-E RIDGE INTO THE SRN BLUE RIDGE. THE 00Z LOCAL WRF PICKED UP ON THIS PRETTY WELL. RADAR TRENDS ARE FINALLY SHOWING SOME WEAKENING AS THE SHOWERS SHIFT EAST TOWARD HENRY COUNTY. ONLY EXPECTING ISOLATED COVERAGE EAST OF THE BLUE RIDGE THRU ABOUT 8 AM. OTHERWISE...WE ARE LOOKING AT PATCHY FOG DEVELOPING WHEN THE MID/HIGH CLOUDS SHIFT EAST. THE MODELS ARE IN REASONABLE AGREEMENT TODAY OF LIFTING A FRONTAL BOUNDARY NORTH THROUGH OUR CWA. MODELS PLACE THE BEST LIFT/THETA-E CONVERGENCE WELL EAST OF US THIS AFTERNOON SO NOT EXPECTING ANY SHOWERS TODAY. SKIES WILL BECOME MOSTLY SUNNY THIS AFTERNOON AND TEMPS WARM CONSIDERABLY TO FRIDAY THANKS TO AN INCREASING WEST FLOW ALOFT...AND RISING HEIGHTS/8H TEMPS. LOOKING AT HIGHS FROM THE LOWER TO MID 80S OVER THE MOUNTAINS AND ADJACENT VALLEYS...TO AROUND 90 ROANOKE AND PIEDMONT. TONIGHT...WILL BE WATCHING UPSTREAM AS MCS IS EXPECTED FOR THE OHIO VALLEY AND MODELS SHIFT THIS AREA EAST AND SOUTH TOWARD SE WV/FAR SW VA BY SUNDAY MORNING. MODELS IN DECENT AGREEMENT THROUGH 12Z SUNDAY IN HITTING SRN OHIO TO ERN KY AND WRN WV WITH BEST COVERAGE...WITH HIGHER THETA-E RIDGE SITUATED ACROSS THIS REGION. GIVEN THAT SYSTEMS TEND TO BE FASTER THAN MODEL FORECAST WILL HAVE POPS UP TO LIKELY IN THE FAR WEST BY MORNING TAPERING TO SLIGHT CHANCE TO THE BLUE RIDGE AND NORTH OF LYH. CONVECTION IS LIKELY TO BE WEAKENING TOWARD MORNING GIVEN LACK OF THERMAL INSTABILITY BUT WIND FIELDS ARE FAVORABLE FOR A FEW STRONG GUSTS. THE STORM PREDICTION CENTER IS KEEPING THE MAIN THREAT OUT OF OUR AREA UNTIL AFTER 12Z SUNDAY...WHICH IS COVERED IN THE NEXT SECTION OF THIS DISCUSSION. LOWS TONIGHT WILL BE MUGGY AS DEWPOINTS INCREASE...MAINLY IN THE 60S CWA WIDE....AROUND 70 SOUTHEAST.
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... AS OF 240 AM EDT SATURDAY... SUNDAY INTO SUNDAY NIGHT CONTINUES TO LOOK LIKE A VERY ACTIVE WEATHER DAY ACROSS AT LEAST THE WESTERN AND NORTHERN PARTS OF THE REGION...WITH A POTENTIAL THUNDERSTORM COMPLEX ENTERING AND MOVING THROUGH THE AREA DURING THE AFTERNOON AND EVENING HOURS. THE NEW DAY 2 CONVECTIVE OUTLOOK BY THE STORM PREDICTION CENTER HAS THE CENTER OF A MODERATE RISK OF POTENTIAL SEVERE WEATHER NEAR THE KY/WV BORDER...WITH THE EASTERN EDGE OF THE MODERATE AREA JUST TOUCHING GREENBRIER COUNTY WV SOUTHWEST INTO TAZEWELL COUNTY VA. THE REMAINDER OF THE FORECAST AREA IS WITHIN THE NEW DAY 2 SLIGHT RISK AREA. DAMAGING WINDS AND LARGE HAIL ARE EXPECTED TO BE THE MAIN THREATS ACROSS THE REGION...WITH AN ISOLATED TORNADO POTENTIAL WITHIN THE MODERATE RISK AREA. THIS SYSTEM WILL BE IN ADVANCE OF A SHORTWAVE TROUGH/LOW THAT WILL HEAD SOUTHEAST THROUGH THE GREAT LAKES REGION SUNDAY NIGHT. IT WILL BE THIS FEATURE THAT MERGES WITH A SOUTHEAST CANADIAN AREA OF LOW PRESSURE THAT YIELDS A LONGWAVE TROUGH ACROSS MOST OF THE EASTERN THIRD OF CONUS...CENTERED OVER OUR REGION...BY MONDAY AFTERNOON. A DECENT GRADIENT WILL EXIST AROUND THE SOUTHERN WAVE FOR THIS TIME OF YEAR TO PRODUCE 850 MB WINDS ON THE ORDER OF 35 TO 45 KTS ACROSS THE AREA LATE SUNDAY...SUNDAY NIGHT...AND EARLY MONDAY TO ALLOW FOR SURFACE GUSTS IN THE 20 TO 30 MPH RANGE AT HIGHER ELEVATIONS DURING THIS PERIOD. WEAK DISTURBANCES WITH IN THE FLOW OF THE PARENT LONGWAVE TROUGH WILL PERIODICALLY PROGRESS TROUGH OUR AREA MONDAY INTO TUESDAY. THE FIRST OF THESE WILL ALLOW FOR SOME SCATTERED SHOWER AND PERHAPS AN ISOLATED THUNDERSTORM ON MONDAY...ESPECIALLY ACROSS THE MOUNTAINS. A LEE TROUGH WILL DEVELOP THANKS TO STRONG W-NW FLOW. AFTERNOON DEVELOPMENT WILL BE POSSIBLE JUST EAST OF THIS TROUGH WHERE LOW LEVEL WINDS WILL BACK SOUTHWEST...AND YIELD A CONVERGENCE LINE ALONG THE TROUGH. MONDAY NIGHT...THE ACTIVE WILL SLOWLY WANE...BUT NOT COMPLETELY END ACROSS THE MOUNTAINS WHERE LINGERING UPPER SUPPORT...AND A NORTHWEST UPSLOPE FLOW WILL HELP MAINTAIN SOME ISOLATED SHOWERS. ON TUESDAY...ANOTHER WEAK DISTURBANCE HEADS SOUTH THROUGH THE AREA...BUT BY THIS TIME...SURFACE HIGH PRESSURE WILL ALSO BE ACROSS THE AREA. WILL LIMIT PRECIPITATION COVERAGE TO ISOLATED SHOWERS ACROSS MAINLY WESTERN AND SOUTHERN PARTS OF THE AREA. THIS ACTIVITY IS EXPECTED TO END BY TUESDAY EVENING. TEMPERATURES DURING THIS PORTION OF THE FORECAST WILL TREND COOLER EACH DAY. TEMPERATURES BY TUESDAY AND TUESDAY NIGHT WILL BE SOME 10 TO 15 DEGREES COOLER THAN THOSE EXPECTED SUNDAY AND SUNDAY NIGHT. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 1245 PM EDT FRIDAY... MODELS DO BRING A COUPLE RE-ENFORCING SHORTWAVES AROUND THE UPPER TROUGH LATE IN THE PERIOD WITH THESE PIVOTING THROUGH THE REGION THURSDAY INTO FRIDAY. HOWEVER MOISTURE LIMITED UNDER THE CONTINUED WEAK RIDGING WITH POPS MAINLY DRIVEN BY COLD AIR ALOFT AND WEAK LOCAL CONVERGENCE MAINLY MOUNTAINS. THUS INCLUDING SOME SLIGHT POPS LATER THURSDAY AND A BIT MORE CHANCE COVERAGE FRIDAY WITH A SECOND STRONGER MID LEVEL WAVE THAT LOOKS TO SHARPEN UP THE TROUGH A LITTLE MORE. BELOW NORMAL TEMPS THE MAIN ASPECT OF NEXT WEEK WITH HIGHS LIKELY A GOOD 5-10 DEGREES BELOW AVERAGE MUCH OF THE PERIOD AND LOWS DIPPING INTO THE 40S AND 50S. COLDEST MORNINGS LOOK TO BE WEDNESDAY AND THURSDAY WHEN THE SURFACE RIDGE WILL BE NEARBY AND 85H TEMPS REMAIN AROUND +10C OVER THE WEST. THIS COULD PRODUCE SOME RECORD LOWS WITH COOP MOS DATA GIVING DEEP VALLEY READINGS WELL DOWN INTO THE 40S. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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AS OF 730 AM EDT SATURDAY... VFR THROUGH EARLY OVERNIGHT. SOME SHALLOW FOG THIS MORNING IS GOING TO BE GONE SOON AND NOT AFFECT TERMINALS. MAIN AVIATION ISSUE SHOULD BE A COMPLEX OF STORMS PROGGED TO IMPACT THE BLF/LWB AREA BY 12Z SUNDAY. CONVECTION MAY BE FASTER SO HAVE -SHRA AND VCTS AT BLF/LWB AT 10Z BUT WITH NO WORSE THAN MVFR CIGS. STORMS WILL DEFINITELY IMPACT THE BLF/LWB AND OVER TOWARD ROA/BCB/LYH THRU SUNDAY...THOUGH MODELS ARE SHOWING IT WEAKENING BEFORE MAKING IT TO THE PIEDMONT. STILL AVIATION INTERESTS SHOULD BE WARY OF POTENTIAL SUB VFR CIGS/VSBYS WITH HEAVY RAIN AND THUNDERSTORMS/WINDS. THE SYSTEM ASSOCIATED WITH THIS WILL BE MOVING ACROSS BY MONDAY...SO THREAT OF SUB VFR THROUGH MONDAY EXPECTED AT MOST TAF SITES...BUT WILL NOT BE CONTINUOUS. SOME GUSTY WINDS BEHIND THE FRONT MONDAY WITH DRIER AIR PUSHING IN FOR TUE-WED...AND MAINLY VFR. CANNOT RULE OUT LATE NIGHT FOG BCB/LWB BUT LOW LVLS MAY STAY DRY ENOUGH FOR LESS FOG COVERAGE.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...WP NEAR TERM...WP SHORT TERM...DS LONG TERM...JH AVIATION...WP

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