Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 150746 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 346 AM EDT MON SEP 15 2014 .SYNOPSIS... HIGH PRESSURE OVER THE AREA THIS MORNING WILL SHIFT EAST AND OFFSHORE THIS AFTERNOON BRINGING WARMER TEMPERATURES AS LIGHT RETURN SOUTHWEST FLOW DEVELOPS. THE NEXT COLD FRONT MOVES THROUGH LATER TONIGHT RESULTING IN A FEW SHOWERS FOLLOWED BY DRIER AND COOLER WEATHER INTO MID WEEK. STRONG HIGH PRESSURE WILL BUILD NORTH OF THE AREA FOR THE REST OF THE WEEK KEEPING RATHER COOL BUT OVERALL DRY WEATHER IN PLACE. && .NEAR TERM /THROUGH TONIGHT/... AS OF 230 AM EDT MONDAY... WEDGE REMAINS IN PLACE EARLY THIS MORNING WITH HIGH PRESSURE STUCK ALONG THE EASTERN SLOPES AND A LIGHT EAST TO SE TRAJECTORY IN PLACE. THIS SHOULD HELP KEEP LOW CLOUDS AND DENSE FOG IN PLACE INTO THE MORNING WITH JUST SOME SPOTTY -DZ OR SPRINKLES SOUTH. CAD FINALLY STARTS TO BREAK DOWN THIS AFTERNOON AS THE SURFACE HIGH SHIFTS EAST AHEAD OF THE NEXT UPSTREAM 5H TROUGH AND ITS WEAK ASSOCIATED COLD FRONT. DEVELOPING WEAK RETURN SOUTH/SW FLOW AHEAD OF THE FRONT LOOKS TO START SCOURING OUT SOME OF THE LOW LEVEL MOISTURE BUT TO WHAT DEGREE REMAINS IN QUESTION. THINK AREAS ACROSS THE FAR NORTH IN THE WAKE OF A PASSING WAVE ALOFT THIS MORNING PER VAPOR LOOP LIKELY TO HAVE MORE SUN WHILE ANY HEATING ELSW WILL ONLY LEAD TO MORE CU DEVELOPMENT. THUS KEEPING IT PARTLY/MOSTLY CLOUDY WITH PWATS STILL RATHER MOIST. SHOWER CHANCES ALSO IFFY GIVEN LITTLE FORCING AND LACK OF SUSTAINED HEATING FOR THE MOST PART. MOST GUIDANCE HAS CUT WAY BACK ON POPS/QPF TODAY WITH ONLY A FEW INCLUDING THE SREF SHOWING SOME DEVELOPMENT SW TIER WHERE ANOTHER WEAK IMPULSE ALOFT ARRIVES LATE. NAM ALSO SHOWS SOME MODEST CAPES OF 500-1K J/KG FROM THE NEW RIVER SOUTH INTO THIS EVENING ALONG A WEAK 85H THETA-E RIDGE BUT LIKELY OVERDONE WITHIN THE CURRENT COOL POOL. THUS CUT BACK POPS TO MOSTLY 20/30 TYPE COVERAGE THIS AFTERNOON/EVENING WITH BEST CHANCES SW AND LEAST OVER THE NE. LEFT SOME ISOLATED THUNDER MENTION IN LATER ON SOUTH BUT THAT MIGHT BE GENEROUS AS WELL. TEMPS MAY FINALLY GET OUT OF THE 60S GIVEN A BUMP IN 85H VALUES UNDER WEAK SW FLOW. HOWEVER IF INSOLATION IS LESS THEN VALUES CLOSER TO THE COOLER EC 2M TEMPS LOOK BEST AND WERE FOLLOWED ESPCLY EAST WHERE CLOUDS MAY LINGER LONGER. WEAK FRONT ZIPS ACROSS FROM THE NW THIS EVENING WITH THE AREA AGAIN BASICALLY IN BETWEEN DEEPER MOISTURE WITH THE RESIDUAL BOUNDARY TO THE SOUTH AND LIMITED LIFT WITH THE UPSTREAM FRONT. GIVEN AN OVERALL WESTERLY TRAJECTORY...DOUBTING MUCH IN THE WAY OF OVERALL SHOWER COVERAGE AFTER EARLY THIS EVENING WITH PERHAPS THE WESTERN SLOPES HAVING THE BEST SHOT LATE AS UPSLOPE INCREASES. THUS THINKING OF GOING FOR JUST ISOLATED COVERAGE AFTER SUNSET AND BETTER CHANCES FAR NW AFTER MIDNIGHT WITH LITTLE POP ELSW LATE BEHIND THE FRONT. LOWS 50S WEST TO LOW 60S EAST AS A NEW ROUND OF COOL ADVECTION STARTS TO ARRIVE LATE. && .SHORT TERM /TUESDAY THROUGH THURSDAY NIGHT/... AS OF 315 AM EDT MONDAY... A COLD FRONT WILL HEAD SOUTH OF THE REGION DURING THE DAY TUESDAY. FORECAST 850 MB NORTHWEST WINDS BEHIND THE FRONT SHOULD YIELD SURFACE GUSTS OF 15 TO 20 MPH ACROSS THE MOUNTAINS DURING THE MORNING HOURS. ALSO...ENOUGH RESIDUAL MOISTURE AND UPSLOPE FLOW WILL HELP MAINTAIN SOME ISOLATED SHOWERS ACROSS PARTS OF SOUTHEAST WEST VIRGINIA...NEIGHBORING COUNTIES OF SOUTHWEST VIRGINIA...AND THE NORTHERN MOUNTAINS OF NORTH CAROLINA PRIMARILY DURING THE MORNING AS WELL. TUESDAY NIGHT THROUGH THURSDAY NIGHT...A BROAD UPPER TROUGH IS FORECAST TO BECOME POSITIONED ACROSS THE U.S. EAST COAST. SURFACE HIGH PRESSURE WILL BUILD OVER PENNSYLVANIA...AND AN ASSOCIATED LEE SIDE TROUGH WILL EXTEND SOUTH THROUGH OUR REGION. WHILE THE FORECAST WILL BE A DRY ONE FOR MUCH OF THE REGION...LOW LEVEL FLOW WILL GRADUALLY TAKE ON PRIMARILY AN E-SE COMPONENT WHICH WILL POOL MOISTURE INTO THE CREST OF THE BLUE RIDGE...ALLOWING FOR THE POTENTIAL FOR SOME UPSLOPE LIGHT RAIN SHOWERS IN THE NORTHERN MOUNTAINS AND FOOTHILLS OF NORTH CAROLINA AND NEIGHBORING PARTS OF SOUTHWEST VIRGINIA. THIS E-SE FETCH MAXIMIZES...AND POTENTIALLY TAPS SOME ATLANTIC MOISTURE ON THURSDAY AND THURSDAY NIGHT. THIS WOULD ALLOW FOR A BIT MORE OF THE REGION...ESPECIALLY ALONG AND NEAR THE CREST OF THE BLUE RIDGE...TO EXPERIENCE SOME ISOLATED SHOWERS. CANNOT RULE OUT SOME ISOLATED THUNDERSTORMS BOTH TUESDAY AFTERNOON AND WEDNESDAY AFTERNOON IN THE NC MOUNTAINS. TEMPERATURES WILL TREND COOLER DURING THIS PORTION OF THE FORECAST BEHIND THE COLD FRONT PASSAGE AND AS DRIER DEW POINT AIR SETTLES INTO THE REGION. && .LONG TERM /FRIDAY THROUGH SUNDAY/... AS OF 345 PM EDT SUNDAY... FOR MOST OF THE LONG TERM PERIOD A BROAD UPPER TROF WILL CONTINUE TO HOLD OVER THE EASTERN U.S. WITH SFC HIGH PRESSURE EXTENDING FROM THE NORTHEAST THROUGH THE MID-ATLANTIC...KEEPING A WEDGE IN PLACE THROUGH THE PERIOD. A REINFORCING SHOT OF DRIER AIR ARRIVES BY FRIDAY AS A NORTHERN STREAM WAVE BRIEFLY AMPLIFIES THE UPPER TROF. ECMWF/GFS ENSEMBLE MEANS AND DETERMINISTIC RUNS NOW SHOW AN UPPER RIDGE TRYING TO BUILD LATE IN THE LONG TERM PERIOD (SATURDAY/SUNDAY) WHICH WILL WEAKEN THE WEDGE OF HIGH PRESSURE AT THE SFC AND ALLOW TEMPS TO MODERATE. UNTIL THEN...TEMPS WILL BE BELOW NORMAL AND MORNING LOWS IN THE 40S WILL BE COMMON FOR MANY MOUNTAIN VALLEY LOCATIONS. OUTSIDE OF UPSLOPE SHOWERS IN THE SOUTHERN BLUE RIDGE/NW NC MOUNTAINS AND FOOTHILLS...MOST AREAS SHOULD REMAIN DRY. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... AS OF 1250 AM EDT MONDAY... WARM AIR ADVECTION OVER THE WEDGE WILL CONTINUE TO LOWER CLOUD BASES ESPCLY OVER THE SOUTH AND WEST THROUGH DAYBREAK WITH ONLY BRIEF BREAKS IN THE CANOPY EXPECTED THROUGH MORNING. THIS WILL BRING WIDESPREAD MVFR/IFR TO MOST LOCATIONS WITH LOWERING STRATUS LEADING TO FOG FORMATION IN SPOTS AND IN ANY LOCATIONS THAT SEE A SPOT OF CLEARING. SOME PATCHY -DZ OR -RA ALSO POSSIBLE BUT MAINLY OUTSIDE OF ANY OF THE TAF LOCATIONS EXCLUDING KDAN AT THIS POINT. MAY EVEN BE LIFR TO VLIFR IN SPOTS AT DAYBREAK WITH MOUNTAIN OBSCURATION LIKELY. ON MONDAY...ONCE THE FOG AND STRATUS LIFT...PERHAPS NOT UNTIL MIDDAY IN SPOTS...CEILINGS AND VISIBILITIES WILL IMPROVE AS THE FLOW TURNS MORE SW. EXPECT MOST TO PUSH INTO VFR DURING THE AFTERNOON WITH CU BASES BETWEEN 4-5K FT WHILE ANY SHRA LOOKS TOO ISOLATED TO INCLUDE FOR NOW. WEAK COLD FRONT SLIDES THROUGH MONDAY EVENING WITH AGAIN MOSTLY ISOLATED SHOWERS BUT LIKELY ENOUGH WESTERLY FLOW TO KEEP THINGS MOSTLY VFR DURING THE EVENING. POTENTIAL FOR LOWER CIGS TO DEVELOP...MAINLY KBLF/KLWB...LOOKS TO COME LATER MONDAY NIGHT WITH INCREASING UPSLOPE FLOW AND PERHAPS A FEW MORE SHOWERS AROUND. EXTENDED AVIATION DISCUSSION... UPSLOPE MOISTURE MAY PERSIST INTO TUESDAY ALONG THE WESTERN SLOPES WHILE EXPECT BRIEF DOWNSLOPE TO BRING MAINLY VFR ELSW INTO TUESDAY AFTERNOON AS WEAK HIGH PRESSURE BUILDS IN. BROAD UPPER TROUGH REMAINS IN PLACE ACROSS THE EASTERN STATES FOR THE REMAINDER OF THE WEEK ALLOWING A LARGE AREA OF HIGH PRESSURE TO BUILD SOUTH FROM THE GREAT LAKES FOR MID WEEK BEFORE WEDGING IN FROM OFF THE MID ATLANTIC COAST BY THE WEEKEND. THIS SHOULD PUSH THE PESKY DEEP MOISTURE FURTHER SOUTH AWAY FROM THE REGION. HOWEVER BIGGER CONCERN WILL BE WITH TRAPPED RESIDUAL LOW LEVEL MOISTURE THAT MAY KEEP SOUTHERN/WESTERN LOCATIONS STUCK IN PERIODS OF MVFR CIGS ESPCLY WEDNESDAY INTO FRIDAY AS THE LOW LEVEL EAST/SE FLOW TAKES SHAPE. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...JH/PH NEAR TERM...JH SHORT TERM...DS LONG TERM...PH AVIATION...AMS/JH/RCS

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