Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 310512 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 112 AM EDT THU JUL 31 2014 .SYNOPSIS...
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AN UPPER TROUGH OF LOW PRESSURE WILL RETROGRADE WEST TO THE MISSISSIPPI RIVER VALLEY...AND THE CENTER OF SURFACE HIGH PRESSURE WILL SHIFT TO OUR EAST. THIS WILL RESULT IN A RETURN OF MOISTURE TO THE REGION ALONG WITH INCREASING CHANCES OF SHOWERS AND THUNDERSTORMS LATER THURSDAY INTO THE WEEKEND.
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&& .NEAR TERM /THROUGH TODAY/... AS OF 1130 PM EDT WEDNESDAY... SHOULD BE A DRY NIGHT OVERALL...WITH A FEW SHOWERS STILL POSSIBLE ACROSS SE WV EARLY. CANT RULE OUT ISOLATED SPRINKLE/SHOWERS OUT EAST AS THETA-E RIDGE AND SOME INCREASE IN DEWPOINTS OCCURS. SKIES FOR MOST OF US WILL BE MAINLY CLEAR THOUGH SOME HIGH CLOUDS ARE A LITTLE THICKER TOWARD THE NC MOUNTAINS. FORECAST LOWS STILL OVERALL LOOKING ONLINE TO REACH THE UPPER 40S DEEPER VALLEYS TO AROUND 60 SOUTHEAST. PATCHY FOG IN THE RIVER VALLEYS SHOULD ALSO FORM GIVEN LIGHT/CALM WINDS. PREVIOUS VALID DISCUSSION... ON THURSDAY...THE TREND TOWARDS E-SE LOW LEVEL FLOW AND GREATER MOISTURE WILL CONTINUE. INCREASING CLOUDS WILL BE THE NORM THROUGHOUT THE DAY WITH UPSLOPE RAIN SHOWERS DEVELOPING AND GROWING IN COVERAGE. THE GREATEST CONCENTRATION WILL BE ACROSS THE NORTHERN MOUNTAINS OF NORTH CAROLINA...NORTHEAST ALONG THE CREST OF THE BLUE RIDGE TO NEAR FLOYD VA. HIGH TEMPERATURES WILL RANGE FROM THE MID 70S TO AROUND 80 IN THE MOUNTAINS TO THE LOW TO MID 80S ACROSS THE PIEDMONT. && .SHORT TERM /TONIGHT THROUGH SATURDAY/... AS OF 330 PM EDT THURSDAY... MODELS CONSISTENT BRINGING A SHORT WAVE THROUGH THE SOUTHWEST FLOW ALOFT THURSDAY NIGHT THROUGH FRIDAY NIGHT. THURSDAY NIGHT AND FRIDAY THERE IS ALSO SOME SUPPORT FROM THE DIFFLUENT AREA OF THE UPPER JET. MAY KEEP PROBABILITY OF THUNDERSTORMS LOW SINCE GUIDANCE IS SHOWING LITTLE CAPE AND INSTABILITY OVER MUCH OF THE FORECAST AREA. BY FRIDAY MORNING...PRECIPITABLE WATER VALUES WILL BE BACK IN THE 1.0 TO 1.5 INCH RANGE WITH SURFACE DEW POINTS IN THE 60S. WPC 24 HOUR QPF FROM 12Z FRIDAY TO 12Z SATURDAY OF 0.25 TO 0.50 INCHES LOOKS REASONABLE. HOWEVER...MODELS DO NOT HAVE A PARTICULARLY GOOD CONSENSUS OF WHERE THE HEAVIEST AMOUNTS WILL BE. EASTERLY COMPONENT OF LOW LEVEL WINDS FAVORS THE EASTERN SLOPES OF THE BLUE RIDGE. PUTTING THE HIGHEST PROBABILITY OF PRECIPITATION IN FROM LATE THURSDAY NIGHT THROUGH LATE MORNING ON FRIDAY. WIDE RANGE IN GUIDANCE FOR MAXIMUM TEMPERATURES ON FRIDAY. WITH ALL THE CLOUDS AND PRECIPITATION EXPECTED...HAVE TRENDED TOWARD THE COOLER BIAS CORRECTED MAV NUMBERS. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... AS OF 330 PM EDT THURSDAY... FRONT AT THE SURFACE REMAINS ALONG THE COAST SATURDAY NIGHT THROUGH MONDAY. ON TUESDAY AND WEDNESDAY...A COLD FRONT WILL PUSH INTO THE REGION FROM THE NORTHWEST. UNTIL THIS FRONT GOES THROUGH...THERE WILL BE A DAILY THREAT OF SHOWERS AND THUNDERSTORMS EACH AFTERNOON AND EVENING. CHALLENGING TO NARROW DOWN WHICH DAY OF TIME FRAME WILL BE MORE FAVORABLE FOR PRECIPITATION...ALTHOUGH MODELS SUGGEST A SHORT WAVE COMING THROUGH THE OHIO VALLEY ON SUNDAY MAY BRING A MORE ORGANIZED AREA OF SHOWERS AND THUNDERSTORMS TO THE COUNTY WARNING AREA. POCKET OF WARMER 850 MB AIR WITH +20 TEMPERATURES COMES OUT OF THE MISSISSIPPI VALLEY...REACHING THE FORECAST AREA ON WEDNESDAY BASED ON THE ECMWF. && .AVIATION /06Z THURSDAY THROUGH MONDAY/...
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AS OF 1255 AM EDT THURSDAY... OVERALL VFR CONTINUES OVERNIGHT WITH SOME INCREASE IN HIGH CLOUDS FROM THE SW THROUGH DAYBREAK ALONG WITH PASSING MID DECK ACROSS THE NW. THIS MAY TEND TO MITIGATE FOG TO SOME EXTENT BUT STILL EXPECTING A PERIOD OF IFR/LIFR AT KLWB BEFORE DAWN...AND MVFR TO BRIEF IFR AT KBCB PENDING DEGREE OF CLOUD COVER. SOME SPOTTY OCNL MVFR ALSO POSSIBLE IN THE EAST AT KLYH/KDAN AROUND SUNRISE WITH MORE COVERAGE AROUND KLYH AT THIS POINT IF AT ALL. ANY LOW CONDITIONS SHOULD FADE BY MID MORNING WITH ANOTHER ROUND OF DEVELOPING 4-6K FT CU FIELDS UNDERNEATH A CI CANOPY INTO THURSDAY AFTERNOON. APPEARS MORE IN THE WAY OF BKN CLOUDS ACROSS THE SW EARLY ON WITH THIS SPREADING NE TO KBLF/KBCB AND KROA THIS AFTERNOON. A FEW SHRA AND ISOLATED TSRA MAY ALSO DEVELOP ALONG THE BLUE RIDGE BUT COVERAGE LACKING AND LIKELY NOT FAR ENOUGH NORTH TO AFFECT MOST TAF SITES LATER THURSDAY SO LEAVING OUT SHOWER MENTION FOR NOW. OTRW VFR WITH WINDS TURN MORE SOUTH TO SW AT 5-10 KTS THIS AFTERNOON. IMPULSE ROUNDING IN FROM THE SW SUPPORTS INCREASING MID CLOUDS THURSDAY EVENING WITH BASES LOWERING OVERNIGHT AS DEEP MOISTURE RETURNS. THIS MAY BRING WIDESPREAD MVFR CIGS TO MUCH OF THE REGION AFTER MIDNIGHT THURSDAY NIGHT WITH IFR IN SHOWERS POSSIBLE ESPCLY ALONG THE BLUE RIDGE BY FRIDAY MORNING. EXTENDED AVIATION DISCUSSION... A BROAD TROUGH OF LOW PRESSURE WILL BE ACROSS THE EASTERN UNITED STATES THROUGH SUNDAY. IT WILL SLOWLY RETROGRADE FROM THE EASTERN/CENTRAL GREAT LAKES TO THE WESTERN GREAT LAKES BY THE WEEKEND. THIS WILL BEGIN TO TURN THE UPPER FLOW TO THE SOUTHWEST WITH TIME. THE AFOREMENTIONED DISTURBANCE COMING FROM THE SE STATES THU...WILL MOVE NORTHEASTWARD ACROSS THE REGION FRI. EXTENSIVE OVERRUNNING LIKELY WITH EMBEDDED ISOLD TSRA. SFC AIR MASS REMAINS QUITE STABLE...ESPECIALLY EAST OF THE ALLEGHANY FRONT...SO THUNDER APPEARS ISOLATED AT THIS POINT. HOWEVER...WIDESPREAD MVFR CIGS/VSBYS WILL BE POSSIBLE FRI WITH THIS SCENARIO IN -RA -DZ BR. FOR SAT-SUN...AIR MASS WILL SLOWLY BECOME WARMER AND MORE UNSTABLE. SCT SHRA/TSRA AGAIN SAT WITH ONLY LIMITED INSTABILITY EVIDENT. FOR SUN...BETTER CHANCE OF TSRA WITH BETTER INSTABILITY ACROSS MUCH OF THE CWA...SW FLOW ALOFT...AND INCREASING MOISTURE LEVELS. THUS...BRIEF PERIODS OF MVFR-IFR CIGS/VSBYS EXPECTED IN SHRA/TSRA SAT AND MORE LIKELY SUN AFTERNOON. SOME DRYING WITH A RETURN TO OVERALL VFR POSSIBLE MONDAY AS ANOTHER WEAK COOL FRONT SWEEPS IN FROM THE NW AND TAKES MOST MOISTURE TO THE SE OF THE REGION. OTHERWISE...POTENTIAL FOR LATE NIGHT/EARLY MORNING IFR- LIFR BR/FG INCREASES THROUGH THE PERIOD...BUT MAINLY AT THE USUAL SITES...LWB/BCB/LYH.
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&& .CLIMATE... JULY 31ST RECORD LOWS: ROANOKE......49...1914 BLUEFIELD....49...1997 DANVILLE.....55...1966 LEWISBURG....48...1997 LYNCHBURG....49...1997 BLACKSBURG...44...1997 && .EQUIPMENT... THE NOAA WEATHER RADIO AT WYTHEVILLE VA...WZ2500...BROADCASTING ON A FREQUENCY OF 162.450 MHZ...IS OFF THE AIR. TECHNICIANS ARE WAITING ON DELIVERY OF PARTS TO MAKE REPAIRS. THE EARLIEST THE RADIO WILL BE WORKING AGAIN IS FRIDAY. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...DS/JH NEAR TERM...DS/WP SHORT TERM...AMS LONG TERM...AMS AVIATION...JH/RAB CLIMATE...PH EQUIPMENT...DS

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