Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 232058 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 458 PM EDT WED JUL 23 2014 .SYNOPSIS... CYCLONIC FLOW ALOFT WILL PREVAIL ACROSS THE EASTERN UNITED STATES THROUGH THURSDAY...DOWNSTREAM OF AN UPPER LEVEL RIDGE ANCHORED OVER THE ROCKIES. WEAK UNIDIRECTIONAL FLOW ALOFT WILL PREVAIL ON FRIDAY AND SATURDAY AS THE UPSTREAM RIDGE FLATTENS AND EXTENDS EASTWARD INTO THE CENTRAL MISSISSIPPI RIVER VALLEY. && .NEAR TERM /THROUGH THURSDAY/...
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AS OF 445 PM EDT WEDNESDAY... SCATTERED THUNDERSTORMS DEVELOPING MAINLY ALONG THE BLUE RIDGE LATE THIS AFTERNOON IN THE WARM AND HUMID AIR MASS WITH SURFACE DEWPOINTS NEARING 70F AND PLENTY OF INSTABILITY. A FEW STORMS COULD BE SEVERE ALONG WITH BRIEF HEAVY RAINFALL WITH ATTENDANT LOCAL RUNOFF ISSUES. SHOULD SEE CONVECTION DIMINISH WITH LOSS OF HEATING LATER THIS EVENING. NEXT QUESTION WILL BE PRECIPITATION CHANCES LATER TONIGHT AND INTO TOMORROW IN ASSOCIATION WITH APPROACHING COLD FRONT AS UPPER TROUGH AMPLIFIES OVER THE GREAT LAKES. FRONTAL BOUNDARY WILL MAKE ITS WAY TOWARD THE WESTERN CWA BY THU MORNING...AND MODELS DEVELOP FAIRLY WIDESPREAD COVERAGE OF PRECIP ACROSS THE WEST EARLY TOMORROW AND SPREADING EAST ACROSS THE PIEDMONT AS THE DAY PROGRESSES. THUNDER MAY BE LIMITED BY CLOUD COVER AND LACK OF INSTABILITY ESPECIALLY ACROSS THE WESTERN HALF OF THE CWA BUT OVERALL CHANCES FOR CONVECTION WILL INCREASE OVER THE PIEDMONT LATER IN THE DAY WITH POSSIBLY SOME HEATING AND MORE INSTABILITY. LOCALLY HEAVY RAINFALL WILL BE POSSIBLE AS WELL WITH STILL VERY HIGH PWATS AHEAD OF THE FRONT. CLOUD COVER AND HIGH DEWPOINTS WILL KEEP LOWS TONIGHT WELL ABOVE NORMAL RANGING FROM MID 60S TO LOWER 70S...WITH DIURNAL RANGE LIMITED TOMORROW AS WELL. HIGHS SHOULD BE 5 TO 8F LOWER THAN TODAYS WARM VALUES.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... AS OF 345 AM EDT WEDNESDAY... WILL START THURSDAY OFF WITH THE COLD FRONT MAKING ITS WAY ACROSS WEST VIRGINIA TOWARD OUR AREA. WITH THE FRONT IN SUCH CLOSE PROXIMITY...WILL ALREADY HAVE SPOTTY SHOWERS AND A FEW THUNDERSTORMS PASSING MAINLY ACROSS THE MOUNTAINS BY SUNRISE...WITH COVERAGE INCREASING THROUGH LATE MORNING AS THE FRONT ENTERS OUR AREA AND DAYTIME HEATING INCREASES. WHILE MUCH OF OUR AREA WILL EXPERIENCE RAINFALL DURING THE MORNING AND AFTERNOON...BELIEVE INSTABILITY WILL BE MORE MUTED COMPARED TO WEDNESDAY DUE IN PART TO THE INCREASED CLOUD COVER. AS SUCH...MOST OF THE THUNDERSTORM ACTIVITY THAT DEVELOPS ACROSS THE MOUNTAINS WILL BE WEAK...ALTHOUGH CANNOT RULE OUT A FEW STRONG STORMS ACROSS THE SOUTHSIDE DURING THE AFTERNOON/ EVENING WHERE HEATING AND INSTABILITY WILL BE STRONGEST. AFTERNOON HIGHS WILL RANGE FROM THE MID 70S ACROSS THE MOUNTAINS TO THE MID 80S ACROSS THE SOUTHSIDE. THE COLD FRONT IS EXPECTED TO SHIFT SOUTH OF OUR AREA THURSDAY NIGHT BEFORE STALLING ACROSS THE CAROLINAS FRIDAY MORNING. REGARDLESS... HIGH PRESSURE BUILDING IN BEHIND THE FRONT IS NOT VERY STRONG...AND WITH MID TO UPPER 60 DEGREE DEWPOINTS LINGERING ACROSS THE SOUTHSIDE...MAY STILL SEE A FEW SHOWERS AND ISOLATED THUNDERSTORMS DEVELOP WITH AFTERNOON HEATING. OTHERWISE...INCREASED SUNSHINE WILL HELP AFTERNOON HIGHS REACH NEAR NORMAL FOR LATE JULY...WITH TEMPERATURES RANGING FROM THE UPPER 70S WEST TO THE UPPER 80S EAST. WIND FLOW ALOFT WILL SHIFT NORTHWESTERLY FRIDAY AS AN UPPER LEVEL TROUGH PASSES EAST ACROSS THE GREAT LAKES...WHILE A LARGE DOME OF HIGH PRESSURE REMAINS SITUATED OVER THE SOUTHWEST U.S. THIS WILL OPEN THE DOOR FOR UPPER LEVEL DISTURBANCES TO ENTER THE AREA FROM THE MIDWEST FOR THE WEEKEND. THE NAM/ECMWF/CANADIAN MODELS ALL ARE PICKING UP ON ONE DISTURBANCE APPROACHING BY SUNRISE SATURDAY...MOST LIKELY TRIGGERING A BAND OF STORMS THAT WILL BE SIGNIFICANTLY WEAKENED AS IT ENTERS OUR SOUTHEAST WEST VIRGINIA/MOUNTAIN EMPIRE COUNTIES. STILL NOT ENTIRELY CONFIDENT IN THIS SCENARIO PLAYING OUT AT THIS POINT...SO WILL STICK WITH A SLIGHT CHANCE OF SHOWERS AND STORMS FOR SATURDAY MORNING. MORE DISTURBANCES ARE SLATED TO ARRIVE ON SATURDAY AND SATURDAY NIGHT...ALTHOUGH TIMING OF THESE DISTURBANCES THIS FAR IN ADVANCE IS ALWAYS DIFFICULT. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... AS OF 400 PM EDT TUESDAY... INTO EARLY NEXT WEEK...THE AREA REMAINS VULNERABLE TO NW FLOW DISTURBANCES TRACKING AROUND THE LARGE WESTERN/CENTRAL CONUS UPPER RIDGE. A PARTICULARLY STRONG DISTURBANCE...NOTED BY ALL THE MODELS...PROMISES TO AMPLIFY THE EASTERN LONG WAVE TROUGH...A FEATURE THAT SHOULD KEEP CONDITIONS UNSETTLED WITH NEAR TO SLIGHTLY BELOW NORMAL TEMPERATURES WHILE THE EXTREME HEAT REMAINS WELL TO OUR WEST AND WELL AWAY FROM OUR PART OF THE COUNTRY. THE BEST CHANCE FOR SHOWERS/STORMS LOOKS TO BE SUNDAY AS THE SURFACE FRONT ASSOCIATED WITH THE STRONG DISTURBANCE CROSSES THE FORECAST AREA FROM THE NORTHWEST. POTENTIAL EXISTS FOR STORMS TO BE ORGANIZED WITH UPSTREAM MCS IMPACTING THE FORECAST AREA. GENERALLY FOLLOWED HPC GUIDANCE THROUGH THE PERIOD. TRENDED POPS UP FOR SUNDAYS FROPA...THEN DOWN FOR A DAY OR TWO AFTER SUNDAYS FRONTAL PASSAGE. TENDENCY FOR FRONTAL PASSAGES IS TO BRING SOME DOWNTIME AS WITH RESPECT TO POPS BEFORE MOISTURE AND INSTABILITY CAN RETURN. && .AVIATION /21Z WEDNESDAY THROUGH MONDAY/... AS OF 125 PM EDT WEDNESDAY... SCATTERED CONVECTION BEGINNING TO DEVELOP ACROSS HIGHER TERRAIN OF WESTERN CWA SO HAVE KEPT VCTS AT ROA/BCB/BLF/LWB WITHIN NEXT 1-2 HOURSRR. THE CONVECTION WILL WANE LATE AFTERNOON/EARLY EVENING BEFORE FRONTAL PRECIP ARRIVES AFTER MIDNIGHT IN THE BLF/LWB CORRIDOR. EXTENDED AVIATION DISCUSSION... NEXT NORTHERN STREAM UPPER TROUGH AND ITS ASSOCIATED COLD FRONT WILL APPROACH WORK THROUGH THE REGION ON THURSDAY. THIS WILL BRING THE BEST CHANCES OF MORE WIDESPREAD SHOWERS TO THE MOUNTAINS AND PERHAPS SOME DEEPER CONVECTION EAST OF THE BLUE RIDGE PENDING TIMING OF THE BOUNDARY THURSDAY AFTERNOON. AIRMASS WILL DRY OUT BEHIND THE FRONT GOING INTO FRIDAY- SATURDAY. OVERALL EXPECT SUB VFR AT TIMES THURSDAY WITH SHRA/TSRA AND MAYBE SOME FOG THU NIGHT...FOLLOWED BY VFR FRI- SAT OUTSIDE OF ANY VALLEY FOG AT KLWB/KBCB EACH MORNING. && .EQUIPMENT... AS OF 405 AM EDT WEDNESDAY... KFCX RADAR IS DOWN. TECHNICIANS WILL AGAIN BE WORKING ON THE RADAR TODAY.. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/WP NEAR TERM...PC/WP SHORT TERM...NF LONG TERM...PM AVIATION...PC/WP EQUIPMENT...PH/WP

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