Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 012214 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 614 PM EDT FRI AUG 1 2014 .SYNOPSIS... A STATIONARY FRONT EXTENDED FROM OFF THE NORTH CAROLINA COAST TO SOUTHERN GEORGIA THIS AFTERNOON WITH HIGH PRESSURE WEDGED FROM NEW JERSEY INTO THE WESTERN CAROLINAS. LITTLE CHANGE IN THE WEATHER PATTERN IS EXPECTED OVERNIGHT. SATURDAY THE WEDGE ERODES AND THE COASTAL FRONT REMAINS TO THE SOUTHEAST. && .NEAR TERM /THROUGH SATURDAY/...
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AS OF 614 PM EDT FRIDAY... CURRENT RADAR SUGGESTS THAT MAIN LIFT WITH UPPER WAVE THAT IS MOVING NORTHEAST OUT OF WRN NORTH CAROLINA IS SHIFTING INTO THE PIEDMONT AREAS AND WHAT UPSLOPE ALONG THE BLUE RIDGE EXISTS THIS EVENING IS PRODUCING RELATIVELY SMALL AREAS OF LIGHT RAIN AND DRIZZLE. MOST OF THE NEAR TERM GUIDANCE THAT IS SIMIALR TO THE RADAR NOW SUGGESTS MUCH OF THIS WILL GRADUALLY WEAKEN BY LATE EVENING WHILE THE MORE MODERATE RAINFALL IN THE EAST QUICKLY SHIFTS OFF TO THE NORTHEAST. HARD TO SEE ANY REASONING FOR MUCH OF ANY SHOWER ACTIVITY DEVELOPING ON THE WEST EDGE OF THE CWA AND THE WEDGE GIVEN THAT DAYTIME INSTABILITY WILL BE LOST SOON. THUS AM LOWERING POPS FOR MOST OF THE WEST TO SLIGHT CHC WITH SOME LOW CHC REMAINING UP ACROSS GREENBRIER IN CASE ANY SHALLOW CONVECTION FARTHER NORTH BACKBUILDS...AND GRADUALLY LOWER THE LIKELY POPS ALONG THE BLUE RIDGE THE CHC OF SHOWERS AND DRIZZLE BY LATE EVENING INTO THE OVERNIGHT. CATEGORICAL FAR EAST FOR JUST ANOTHER COUPLE HOURS THEN DROPPING OFF TO MID CHC...AND WILL DETERMINE LATE IF WE NEED TO DROP THAT EVEN MORE FOR MUCH OF THE OVERNIGHT WHEN THIS UPPER WAVE HAS MOVED OFF...LEAVING WEAKENING UPSLOPE ALONG BLUE RIDGE AS 850 FLOW TURNS MORE SW BEHIND IT. DON`T THINK THIS SW FLOW WILL BE ABLE TO ERODE THE WEDGE OVERNIGHT HOWEVER...SO AM KEEPING CLOUDS AND AREAS OF DRIZZLE AND FOG IN ALL NIGHT. MADE SOME MINOR ADJUSTMENTS TO SKY COVER ON WESTERN FRINGE WHERE SOME PARTIAL CLEARING HAS TAKEN PLACE ON THE EDGE OF THE WEDGE...BUT THIS MAY FILL BACK IN AFTER DARK. ALSO PULLED MENTION OF HEAVY RAINFALL FROM THE HWO AS THERE ARE EXPECTATIONS OF RAINFALL RATES HIGH ENOUGH TO CAUSE EVEN MINOR ISSUES EXCEPT FOR SOME PONDING IN LOW-LYING STREETS IN THE EAST. PREV DISCUSSION AS OF 340 PM EDT FRIDAY... TWO DISTINCT SHORT WAVES SEEN ON THE WATER VAPOR LOOP THE FIRST MOVING ACROSS WEST VIRGINIA AND VIRGINIA HELPED GENERATE THE LARGE SHIELD OF RAIN FROM THIS MORNING. THE SECOND VORTICITY MAXIMUM WAS APPROACHING SOUTH CAROLINA AND WAS FORECAST TO MOVE INTO VIRGINIA OVERNIGHT. BUFKIT FORECAST SOUNDINGS SHOWED NORTHEAST WINDS AT THE SURFACE EAST OF THE BLUE RIDGE...20-25 KNOT EAST TO SOUTHEAST 850 MB WINDS TONIGHT AND SOUTHWEST WINDS ALOFT. THIS TRANSITIONS TO SOUTHWEST WINDS AT 850 MB AS THE WEDGE AND MOISTURE BECOMES SHALLOW ON SATURDAY. THE COMBINATION OF LIFT FROM THE CAROLINA WAVE AND UPSLOPE FLOW WILL RESULT IN RAIN ALONG AND EAST OF THE BLUE RIDGE TONIGHT. MOST OF THE SHORT TERM GUIDANCE HAD THE MORE WIDESPREAD AND STEADIER LIGHT TO MODERATE RAIN MOVING NORTHEAST OUT OF THE FORECAST AREA AFTER MIDNIGHT. THEN OVERNIGHT...PRECIPITATION WILL BE MORE SPOTTY LIGHT RAIN AND DRIZZLE. ALSO ADDED AREAS OF FOG IN THE TYPICAL AREAS WHERE THE WEDGE IS IN PLACE. TEMPERATURES ON SATURDAY WILL BE DEPENDENT ON WHEN WEDGE ERODES. EXPECTING TYPICAL SOUTHWEST TO NORTHEAST PROGRESSION...WITH LYNCHBURG AND THE NORTHEAST COUNTIES OF THE FORECAST AREA THIS LAST TO BREAK OUT.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... AS OF 250 PM EDT FRIDAY... THROUGHOUT MOST OF THIS PORTION OF THE FORECAST...THE AXIS OF THE ESTABLISHED UPPER LEVEL TROUGH WILL REMAIN POSITIONED JUST WEST OF THE FORECAST AREA. THIS WILL CONTINUE TO ALLOW FOR A GOOD MOISTURE FETCH OFF THE ATLANTIC TO PROGRESS INTO THE REGION. THE INTERPLAY OF UPSLOPE CONDITIONS ALONG AND NEAR THE CREST OF THE BLUE RIDGE AND WEAK DISTURBANCES ROUNDING THE BASE OF THE MAIN TROUGH AXIS...WILL KEEP THE CHANCE OF SHOWERS AND AFTERNOON/EARLY EVENING ISOLATED THUNDERSTORMS ACROSS OUR AREA DURING THIS PERIOD. WHILE THE MAIN UPPER TROUGH WILL REMAIN TO OUR WEST...THERE WILL BE A CHANGE IN JUST HOW THIS FEATURE IS MATERIALIZED. THROUGH ROUGHLY FRIDAY MORNING...THE FEATURE WILL BE THE BASE OF A CLOSE LOW SYSTEM NEAR HUDSON BAY CANADA. THIS LOW HOWEVER WILL SHIFT EAST BY THE START OF THE WEEKEND...ALLOWING THIS MAIN UPPER TROUGH TO FADE IN INTENSITY ONLY BRIEFLY. BY SUNDAY...THE REMNANT OF THIS FIRST UPPER TROUGH WILL BE STRENGTHENED BY A SHORTWAVE TROUGH PROGRESSING EASTWARD INTO THE TENNESSEE AND OHIO VALLEYS FROM THE WEST. DESPITE THIS FLUCUATION...THE OVERALL FORECAST WILL BE AS DESCRIBED ABOVE. THE TIME PERIOD WHEN PRECIPITATION CHANCES WILL BE AT THEIR LOWEST IS MONDAY NIGHT WHEN THE LATEST GUIDANCE OFFERS A SOLUTION OF BROADENING THE WIDTH OF THE TROUGH...AND SHIFTING THE AXIS A LITTLE FARTHER EAST. THIS IS EXPECTED TO HAVE THE RESULT OF LIKEWISE SHIFTING THE BEST CHANCES OF PRECIPITATION EAST OF THE FORECAST AREA. && .LONG TERM /TUESDAY THROUGH FRIDAY/... AS OF 1230 PM EDT FRIDAY... AT THE SURFACE TUESDAY...HIGH PRESSURE SITS OVER WEST VIRGINIA WHILE A SLOW MOVING COLD FRONT IS ACROSS THE OHIO VALLEY. TS BERTHA OR WHAT IS REMAINING OF IT IS FORECAST TO REMAIN WELL OFF SHORE AND WILL NOT BE A FACTOR IN OUR REGION NEXT WEEK. AN UPPER LEVEL TROUGH REMAINS SITUATED ACROSS THE EASTERN US. THE UPPER LEVEL FLOW WILL BECOME MORE ZONAL BY THE END OF THE PERIOD. THE FRONT ACROSS THE OHIO VALLEY WILL SLOWLY DRIFT AND PARTIALLY STALL OUT ACROSS NORTHERN PORTIONS OF OUR CWA BY THURSDAY INTO FRIDAY. WHILE PWATS ARE NOT IMPRESSIVE...GENERALLY 0.75-1.25 INCHES DEPENDING ON THE LOCATION...EXPECT ISOLATED TO SCATTERED THUNDERSTORMS EACH AFTERNOON BEGINNING DURING PEAK HEATING AND TAPERING OFF AROUND SUNSET. FOCUS OF THE LOW CHANCE POPS ARE ACROSS THE MOUNTAINS AND GENERALLY NORTH OF ROUTE 460. SURFACE TEMPS WILL BE RIGHT AROUND NORMAL FOR THE PERIOD. 850MB TEMPS OF +15-17C WILL CORRESPOND TO SURFACE HIGHS OF MID TO UPPER 80S EAST OF THE BLUE RIDGE AND LOWER 80S ACROSS THE MOUNTAINS. DEWPTS IN THE UPPER 50S TO LOWER 60S WILL KEEP NIGHT TIME TEMPS UP A BIT. && .AVIATION /22Z FRIDAY THROUGH WEDNESDAY/... AS OF 145 PM EDT FRIDAY... COMBINATION OF UPSLOPE LOW LEVEL FLOW AND LOFT FROM TWO SHORT WAVES CROSSING THE AREA...POOR FLYING CONDITIONS WILL CONTINUE ACROSS MUCH OF THE REGION TONIGHT. THE BEST COVERAGE OF RAIN WILL BE ALONG AND EAST OF THE BLUE RIDGE BEFORE 06Z/2AM TONIGHT. AFTER SUNSET...CEILINGS WILL DROP AND REMAIN AT IFR TO LIFR LEVELS WITH AREAS OF FOG AND DRIZZLE. BOTH THE NAM AND GFS SHOWED THE MAJORITY OF THE HEAVIER PRECIPITATION MOVING NORTHEAST AND OUT OF SOUTHWEST VIRGINIA BY 09Z/5AM. LOWER CONFIDENCE ON HOW FAST WEDGE WILL ERODE ON SATURDAY. BUFKIT FORECAST SOUNDINGS SUGGEST SURFACE AND LOW LEVEL WINDS WILL COME AROUND TO THE SOUTHWEST AFTER 15Z/11AM. EXPECT KLYH WILL BE THE LAST AIRPORT TO LIFT OUT OF IFR CONDITIONS. EXTENDED AVIATION DISCUSSION... THE BROAD UPPER TROUGH OF LOW PRESSURE WILL LINGER ACROSS THE EASTERN UNITED STATES THROUGH SUNDAY CONTINUING TO RETROGRADE FROM THE EASTERN/CENTRAL GREAT LAKES TO THE WESTERN GREAT LAKES BY THE WEEKEND. SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS ARE EXPECTED AGAIN ON SUNDAY. FOR MONDAY AND TUESDAY...THE AIR MASS WILL SLOWLY BECOME WARMER AND MORE UNSTABLE. ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE EXPECTED IN THE AFTERNOON AND EVENING...ESPECIALLY TUESDAY...WITH BRIEF PERIODS OF MVFR- IFR CIGS/VSBYS EXPECTED IN SHRA/TSRA. A WEAK COLD FRONT MOVES SLOWLY SOUTH FROM THE OHIO VALLEY ACROSS THE MID ATLANTIC REGION...THIS WILL ALSO BRING A CHANCE OF SHOWERS AND THUNDERSTORMS. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS/SK SHORT TERM...DS LONG TERM...CF AVIATION...JH/NF/WP

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