Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 141157 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 757 AM EDT SUN SEP 14 2014 .SYNOPSIS... COOL HIGH PRESSURE WILL SLIDE EAST FROM THE OHIO VALLEY OVER THE MID ATLANTIC TODAY AND THEN SHIFT EAST ALONG THE ATLANTIC COAST BY MONDAY. THIS WILL ALLOW TEMPERATURES TO WARM AGAIN AS WINDS SHIFT MORE SOUTHWEST. THE NEXT COLD FRONT MOVES THROUGH EARLY TUESDAY MORNING BRINGING COOLER THAN NORMAL TEMPERATURES FOR THE REMAINDER OF THE WEEK...BUT A FEW SHOWERS OR A STRAY THUNDERSTORM COULD FORM AHEAD OF THIS LATE MONDAY AND MONDAY NIGHT. && .NEAR TERM /THROUGH TONIGHT/... AS OF 702 AM EDT SUNDAY... VERY LIGHT AND ISOLATED SHOWERS CONTINUE TO SPREAD NORTHEAST UP THROUGH SW VA. CEILINGS IN THE OBS DO NOT SUGGEST THERE IS REALLY MUCH DRIZZLE...SO HAVE REMOVED DRIZZLE AND INCLUDED SOME SPRINKLES OUTSIDE THE AREAS OF SLIGHT CHC...AND SHIFTED THIS A LITTLE FARTHER NORTH FOR A FEW HOURS THIS MORNING. AS AREA OF STRATUS ASSOCIATED WITH NE FLOW AND WEDGE HAS MOVED INTO WV...FOG IS LESS OF AN ISSUE NOW...AND HAVE MADE SOME ADJUSTMENTS TO CUT THIS BACK AS WELL. THINKING IS THAT AS THE MORNING PROGRESSES THESE ISOLATED SHOWERS MAY FADE OUT...BUT THEN DIURNAL SHOWERS...PERHAPS A LITTLE MORE SCATTERED...WILL DEVELOP NEAR THE WESTERN PERIPHERY OF THE WEDGE IN FAR SW VA AND HIGHER ELEVATIONS OF NW NC. NO OTHER CHANGES TO FCST AT THIS TIME. PREV DISCUSSION AS OF 400 AM EDT SUNDAY... COOL WEDGE IN PLACE THROUGH TODAY AND TONIGHT...BUT SOME DRIER AIR ADVECTING IN FROM NORTHEAST SHOULD HELP TO ERODE CLOUDS A LITTLE QUICKER ACROSS PARTS OF THE NORTH...SO DAY TIME TEMPS MAY END UP BEING A BIT WARMER ACROSS MUCH OF THE NORTH AND NORTHEAST AREA THAN FARTHER SOUTH. MUCH CLOUD COVER WITH LIGHT NE FLOW WILL CONTINUE ALONG BLUE RIDGE AND INTO NEW RIVER VALLEY...SO WENT AT OR EVEN A TAD BELOW COOLER MET GUIDANCE THERE...TRENDING MORE TOWARD WARMER MAV GUIDANCE ACROSS THE NORTH. LOW CONFIDENCE FORECAST THOUGH GIVEN SOME POTENTIAL FOR PARTIAL CLEARING EVEN FARTHER SOUTH. VERY WEAK UPPER WAVE RIDES ACROSS SHALLOW WEDGE DURING THE DAY AND SOME MODELS STILL SQUEEZE OUT SOME LIGHT SHOWER ACTIVITY...MAINLY FAR SW PORTION OF FCST AREA. IF WEDGE WEAKENS MORE RAPIDLY THAN EXPECTED EARLIER IN THE DAY...THIS LIFT PROVIDED BY WAVE MAY HAVE LESS SHALLOW LIFT AND THUS LITTLE OR NO SHOWER ACTIVITY WOULD FORM. MAINLY KEEPING WITH FAIRLY SMALL AREA OF SLIGHT CHC POPS...WITH EVEN SMALLER AREA OF LOW CHC POPS HIGHER ELEVATIONS OF NW NC THIS AFTERNOON. DO NOT SEE ANY INSTABILITY TO CONSIDER MENTIONING THUNDER. MIN TEMPS TONIGHT DEPEND LARGELY AGAIN ON CLOUD COVER...AND AGAIN THIS SHOULD BE MOST LIKELY FIRMLY IN PLACE ACROSS THE SOUTH AND ESPECIALLY UP AGAINST THE BLUE RIDGE IN NC AND FAR SW VA AS WEAK WEDGE HOLDS ON...BUT WILL LIKELY HAVE MORE CLEARING ACROSS THE NORTHERN HALF...SO SOME UPPER 40S IN MTN VALLEYS QUITE POSSIBLE IF IT REMAINS MAINLY CLEAR MOST OF THE NIGHT...GREENBRIER VALLEY MOST LIKELY. IF CLOUDS REMAIN FARTHER NORTH THEN MID 50S MAY BE AS COOL AS WE CAN GET ANYWHERE. && .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... AS OF 300 AM EDT SUNDAY... ON MONDAY...HIGH PRESSURE WILL BECOME CENTERED ALONG THE EAST COAST FROM THE CAROLINAS TO NEW ENGLAND. AN UPPER LEVEL TROUGH AN ASSOCIATED SURFACE COLD FRONT WILL BE APPROACHING FROM THE NORTHWEST. BETWEEN THESE TWO FEATURES...LOW LEVEL FLOW ACROSS THE AREA WILL BECOME SOUTHWEST...AND THEN GRADUALLY MORE WEST AS WE HEAD INTO MONDAY NIGHT. THE RESULT WILL BE INCREASE IN MOISTURE AND INSTABILITY ACROSS THE AREA...ESPECIALLY NEAR THE CREST OF THE BLUE RIDGE WHERE DIFFERENTIAL HEATING AND OROGRAPHICAL INFLUENCE WILL ACT AS A FOCUS FOR AFTERNOON CONVECTION. WHILE ISOLATED SHOWERS ARE EXPECTED IN THE MORNING...BY THE AFTERNOON...ISOLATED STORMS WILL BE MIXED WITH ISOLATED TO SCATTERED SHOWERS. BY MONDAY NIGHT...THE FOCUS FOR THE BEST COVERAGE SHIFTS TO THE EASTERN PART OF THE REGION WITH THE APPROACH OF THE FRONT...AND ALSO TO THE PREFERRED UPSLOPE REGIONS OF SOUTHEAST WEST VIRGINIA ONCE WINDS SHIFT NORTHWEST AND INCREASE POST-FRONT THE THE LATTER HALF OF MONDAY NIGHT. DURING THE DAY TUESDAY...SURFACE WINDS MAY GUST TO 10 TO 15 MPH ACROSS THE MOUNTAINS WITH 850 WINDS NEAR 20 KTS. PRECIPITATION WILL BE SHUNTED SOUTH OF THE REGION DURING THE MORNING AHEAD OF THE DEPARTING COLD FRONT. BY THE AFTERNOON...THE FRONT MAY STILL BE IN CLOSE ENOUGH PROXIMITY TO THE SOUTHWESTERN PARTS OF THE REGION FOR ASSOCIATED CONVECTION ALONG IT TO STILL BE OVER PARTS OF THE NORTHERN MOUNTAINS AND FOOTHILLS OF NORTH CAROLINA. TUESDAY NIGHT INTO WEDNESDAY NIGHT...HIGH PRESSURE SETTLES OVER CENTRAL VIRGINIA. ANTI-CYCLONIC FLOW AROUND IT WILL HELP ADVECT MOISTURE...AND PERHAPS THE WESTERN EXTENT OF THE FRONT...BACK NORTH INTO THE REGION...ESPECIALLY THE SOUTHWESTERN PORTION OF THE REGION. THIS COULD BRING ADDITIONAL ISOLATED TO SCATTERED SHOWERS TO THIS PART OF THE AREA ALONG WITH SOME ISOLATED THUNDERSTORMS DURING THE AFTERNOON WEDNESDAY. TEMPERATURES DURING THIS PORTION OF THE FORECAST WILL BE SLIGHTLY ABOVE NORMAL ON MONDAY...BUT TREND COOLER BEHIND THE FRONT TUESDAY AND WEDNESDAY TO READINGS NEAR NORMAL FOR THIS TIME OF THE YEAR. && .LONG TERM /THURSDAY THROUGH SATURDAY/... AS OF 345 PM EDT FRIDAY... THIS PATTERN CONTINUES ON THURSDAY. TEMPS FOR THURSDAY WILL BE HIGHLY DEPENDENT ON CLOUD COVER. WITH THE POTENTIAL FOR LOW CLOUDS IN EASTERLY FLOW...TRENDED TOWARD THE COOLER ECMWF GUIDANCE FOR TEMPS DURING THIS PERIOD. ECMWF AND GFS BOTH STRENGTHEN THE WEDGE ON FRIDAY...WHICH WILL BRING COOLER TEMPS TO THE AREA...AND PUSHES MOISTURE SOUTH AND WEST. CONTINUED TO LEAN TOWARD COOLER ECMWF VALUES FOR HIGHS. MODELS HINTS AT ANOTHER UPPER LEVEL SYSTEM MOVING INTO THE REGION EARLY NEXT WEEKEND...THAT WOULD REINFORCE THE UPPER LEVEL TROF OVER OUR AREA. && .AVIATION /12Z SUNDAY THROUGH THURSDAY/... AS OF 755 AM EDT SUNDAY... LOW TO MID STRATUS DECK IN ASSOCIATE WITH COOL HIGH PRESSURE WEDGE FROM THE NORTH-NORTHEAST HAS SPREAD ACROSS MOST OF THE TAF SITES...WITH MVFR TO VFR CIGS. ANY FOG AT AIRPORTS THIS MORNING WILL BE MINIMAL TO NON-EXISTENT AND LIKELY MVFR...BUT CANT RULE OUT AN HOUR OF IFR FOG STILL AT LWB...BLF...OR BCB IF THIS STRATUS DECK WERE TO BRIEFLY LIFT BEFORE 13 UTC. OTHERWISE CIGS SHOULD LIFT TO VFR EVERYWHERE BY MID AFTERNOON...IF NOT EARLIER WITH SOME DIURNAL MIXING. ROA AND LYH...PERHAPS ALSO LWB...MAY EVEN GO SCATTERED WITH SOME DRIER AIR TRYING TO MIX IN FROM THE NORTHEAST. WINDS WILL REMAIN LIGHT FROM NORTHEAST...BUT MAY SHIFT TO SOUTHWEST IN MTN LOCATIONS LATER IN AFTERNOON AS SFC HIGH WEAKENS AND CONTINUES SLIDING EAST. BY EVENING...WINDS WILL QUICKLY GO NEARLY CALM...AND FCST CHALLENGE IS HOW SOON MVFR TO IFR CIGS OR VSBYS MAY COME BACK WITH VERY WEAK WEDGE STILL HOLDING ON. CONFIDENCE IN THESE CONDITIONS RETURNING IS FAIRLY LOW. SOME CLEARING ACROSS NORTH MAY GIVE LWB BEST CHANCE FOR IFR FOG...BUT WILL PUT BCB DOWN LOW AS WELL DUE PARTLY TO CLIMATOLOGY AND POSSIBILITY OF SOME PARTIAL CLEARING...BUT THIS IS LOWER CONFIDENCE. OTHERWISE MVFR CIGS AT OTHER TAF SITES ARE A DECENT BET OVERNIGHT WITH WEAK WEDGE. A FEW SPRINKLES AROUND THIS MORNING BUT ONLY PUT IN VCSH FOR AN HOUR OR TWO THIS MORNING...THEN CANNOT RULE OUT A POP UP SHOWER LATER THIS AFTERNOON ACROSS FAR WEST...WITH BLF AND BCB THE ONLY AIRPORTS THAT COULD BE IMPACTED...BUT SO ISOLATED NOT CONFIDENT ENOUGH TO PUT IN TAF. EXTENDED AVIATION DISCUSSION... BY LATE MONDAY...WEAK UPPER SHORT WAVE AND ASSOCIATED WEAK SFC FRONT SLIDE THROUGH AND MAY BRING AN ISOLATED SHOWER TO THE MOUNTAINS MAINLY...AND THEN A BROAD UPPER TROUGH DEVELOPS ACROSS THE NORTHERN STATES...WITH THE RNK CWA ON THE SOUTHERN EDGE OF THIS BROAD UPPER TROUGH. BEHIND THIS SHOWER WAVE ON MONDAY PATTERNS IS TRENDING TOWARD A MORE NW FLOW ALOFT AS THE WEEK PROGRESSES...WHICH SHOULD ATTEMPT TO PUSH THE PESKY DEEP MOISTURE FURTHER SOUTH AWAY FROM THE REGION. THIS PATTERN WOULD BE DRY WITH LIGHT NW WINDS...BUT MAY TEND TO KEEP MVFR CIGS IN THE WEST. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...SK NEAR TERM...SK SHORT TERM...DS LONG TERM...PH AVIATION...RCS/SK

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