Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 131402 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 1002 AM EDT SAT SEP 13 2014 .SYNOPSIS... A COLD FRONT THIS MORNING WILL BRING CANADIAN HIGH PRESSURE ACROSS OUR AREA TODAY. THIS HIGH PRESSURE WILL PASS FROM THE GREAT LAKES TO NEW ENGLAND TONIGHT...AND THEN BUILD SOUTHWARD ACROSS THE MID ATLANTIC FOR SUNDAY...PROVIDING COOLER THAN NORMAL TEMPERATURES. WARMER WEATHER RETURNS FOR MONDAY AS HIGH PRESSURE MOVES OFFSHORE...ALLOWING WINDS TO SHIFT SOUTHWESTERLY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 955 AM EDT SATURDAY... TNB...LWB...BLF AND PSK HAVE SHIFTED TO A NORTHWEST WIND AS A WEAK BOUNDARY CROSSES THROUGH THE AREA. THIS ROUGHLY LINES UP WITH THE BACK EDGE OF THE BETTER COVERAGE OF PRECIPITATION. RADAR TRENDS SINCE 8AM SHOWED THE WESTERN EDGE OF THE PRECIPITATION MOVING NORTHEAST AROUND 30 MPH. AS LONG AS THE BAND OF SHOWERS AND ISOLATED THUNDERSTORMS CONTINUE MOVING AT THIS SPEED AND DIRECTION...THE BULK OF THE PRECIPITATION WILL BE EXITING THE EASTERN COUNTY WARNING AREA AROUND 18Z/2PM. HAVE ADJUSTED PROBABILITY OF PRECIPITATION FOR THESE TRENDS. ONLY MINOR ADJUSTMENTS MADE TO MAXIMUM TEMPERATURES FOR TODAY. NORTHWEST WINDS WILL AIDE IN EXPANDING BREAKS IN THE CLOUD COVER JUST EAST OF THE BLUE RIDGE THIS AFTERNOON. CANADIAN HIGH PRESSURE BUILDING IN BEHIND THE COLD FRONT WILL PUSH ACROSS THE LOWER GREAT LAKES THIS EVENING AND TONIGHT... GRADUALLY SHIFTING WINDS ACROSS OUR AREA FROM NORTHWESTERLY BY SUNSET TO NORTHEASTERLY BY SUNRISE SUNDAY. WHILE MUCH OF OUR AREA WILL BE DRY SATURDAY NIGHT...LOOKS LIKE THERE WILL BE ENOUGH RESIDUAL MOISTURE BEING FORCED UP THE BLUE RIDGE BY SUNDAY MORNING TO SUPPORT LIGHT RAIN ACROSS THE NORTH CAROLINA MOUNTAINS. && .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... AS OF 345 AM EDT SATURDAY... ON SUNDAY MORNING...HIGH PRESSURE WILL BE IN THE PROCESS OF SHIFTING FROM THE GREAT LAKES INTO NEW ENGLAND...AND WILL THEN BEGIN TO BUILD SOUTHWARD ACROSS THE MID ATLANTIC TO BUTT UP AGAINST THE EASTERN FACE OF THE APPALACHIANS. FORECAST MODELS HAVE BECOME MORE AGGRESSIVE IN PUSHING THE COLD FRONT FURTHER SOUTH OF OUR AREA COMPARED TO MODEL RUNS FROM 24 HOURS AGO...INDICATING THAT DRIER AIR WILL BE IN PLACE FOR SUNDAY WITH LOWER RAIN CHANCES OUR FORECAST REGION. THE CAVEAT TO THAT STATEMENT LIES IN THE NORTH CAROLINA MOUNTAINS...WHERE NORTHEASTERLY WINDS WRAPPING AROUND THE HIGH WILL CARRY MARINE AIR UP THE BLUE RIDGE...SUPPORTING MORNING DRIZZLE AND AFTERNOON SPOTTY SHOWER ACTIVITY THAT MAY BECOME MODERATE IN INTENSITY FOR BRIEF PERIODS OF TIME. WITH HIGH PRESSURE IN PLACE... ALSO CONTINUING THE TREND OF UNDERCUTTING MODEL GUIDANCE FOR AFTERNOON TEMPERATURES...HOLDING HIGHS TO THE MID/UPPER 60S MOST LOCATIONS. THE EXCEPTION MAY BE ACROSS PORTIONS OF THE MOUNTAIN EMPIRE WHICH ARE BUFFERED FROM THE COOL HIGH PRESSURE BY THE HIGHER RIDGELINES. TEMPERATURES WEST OF THESE RIDGES MAY WARM INTO THE MID 70S IF THE SUN BREAKS OUT OF THE CLOUDS. ON MONDAY...HIGH PRESSURE WILL MOVE OFFSHORE...ALLOWING WINDS TO SHIFT SOUTHWESTERLY AS ANOTHER UPPER LEVEL DISTURBANCE AND ASSOCIATED COLD FRONT APPROACH FROM THE MIDWEST. SOUTHWESTERLY FLOW WILL RETURN GULF MOISTURE NORTHWARD ALONG THE APPALACHIAN CHAIN...WHICH WILL PUSH DEWPOINT TEMPERATURES BACK INTO THE 60S ACROSS MUCH OF THE AREA AND PRECIPITABLE WATER VALUES INTO THE 1.1 TO 1.5 INCH RANGE. AND WITH MONDAY AFTERNOON TEMPERATURES WARMING INTO THE MID TO UPPER 70S...BELIEVE WE WILL HAVE ENOUGH INSTABILITY TO SUPPORT SCATTERED SHOWERS AND POSSIBLY A THUNDERSTORM OR TWO MONDAY EVENING AS THE FRONT NEARS OUR AREA. THE COLD FRONT WILL PASS ACROSS OUR AREA MONDAY NIGHT...ALLOWING DRIER AIR TO WORK IN FROM THE GREAT LAKES REGION. INCREASED SUNSHINE ON TUESDAY WILL ALLOW AFTERNOON TEMPERATURES TO REACH THE UPPER 60S/LOW 70S ACROSS THE MOUNTAINS...AND RISE INTO THE MID/UPPER 70S ACROSS THE PIEDMONT. TUESDAY NIGHT LOWS WILL BE GENERALLY IN THE 50S. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... AS OF 130 PM EDT FRIDAY... A BROAD UPPER TROUGH WILL GRADUALLY DEEPEN ACROSS THE EASTERN STATES NEXT WEEK...ALLOWING A LARGE AREA OF HIGH PRESSURE PASSING ACROSS THE GREAT LAKES TO EVENTUALLY WEDGE SOUTH ALONG THE MOUNTAINS BY NEXT WEEKEND. THIS SHOULD PROMOTE MAINLY DRY WEATHER...ALTHOUGH CANNOT TOTALLY RULE OUT ISOLATED SHOWERS DURING THE SECOND HALF OF THE WEEK OVER THE SOUTH PER ANOTHER PASSING SHORTWAVE...BUT THIS APPEARS REMOTE GIVEN DRY AIR AND LATEST MODEL TRENDS. THUS PLANNING TO KEEP THE END OF THE WEEK MOSTLY DRY OUTSIDE OF AN ISOLATED SHOWER MENTION FAR SOUTH-EAST WEDNESDAY-EARLY THURSDAY. HIGHS MAINLY MID 60S TO AROUND 70 WEST AND 70-75 EAST WITH LOWS MOSTLY 50S...EXCEPT FOR A FEW COOLISH 40S IN THE VALLEYS GIVEN THE SURFACE RIDGE AXIS ABOUT OVERHEAD. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/... AS OF 730 AM EDT SATURDAY... IFR CONDITIONS ARE WIDESPREAD THIS MORNING AS DEEP GULF MOISTURE POOLS AHEAD OF AN APPROACHING COLD FRONT. THE ABUNDANT MOISTURE HAS RESULTED IN AREAS OF SHOWER ACTIVITY WHICH WERE VERY EFFICIENT AT PRODUCING HEAVY RAIN OVERNIGHT...LIMITING VISIBILITIES TO 1SM OR LESS AT TIMES. SEVERAL AIRPORTS ARE ALSO REPORTING FOG...MAINLY ACROSS THE MOUNTAINS...WHERE THE TERRAIN IS INTERSECTING WITH THE LOW CEILINGS. IMPROVING CONDITIONS ARE EXPECTED BEGINNING BY AROUND 14Z AS A COLD FRONT ENTERS SOUTHEAST WEST VIRGINIA...AND PUSHES RAPIDLY EAST. SHORT RANGE FORECAST MODELS INDICATE THAT THE SHOWER ACTIVITY MOVING ACROSS SOUTHEAST WEST VIRGINIA AND VIRGINIA AT SUNRISE WILL GRADUALLY DIMINISH THROUGH THE MORNING...RESULTING IN ONLY SPOTTY SHOWERS DURING THE AFTERNOON. THE FRONT WILL BRING A NORTHWESTERLY WIND SHIFT THROUGH LATE MORNING AND THE AFTERNOON THAT WILL CARRY DRIER AIR INTO THE REGION...ALLOWING CEILINGS TO IMPROVE TO MVFR ACROSS THE MOUNTAINS...PERHAPS LOW VFR ACROSS THE PIEDMONT...BY LATE AFTERNOON. HIGH PRESSURE WILL SHIFT QUICKLY ACROSS THE GREAT LAKES TO NEW ENGLAND THIS EVENING...AND THEN WEDGE SOUTHWARD TO THE MID ATLANTIC TONIGHT. THIS WILL BRING WINDS INCREASINGLY NORTHEASTERLY THROUGH THE LATER HALF OF THE TAF PERIOD. THE NORTHEASTERLY FLOW WILL RETURN MARINE AIR INTO THE AREA...WHERE IT WILL BANK AGAINST THE BLUE RIDGE. EXPECT SCATTERED MVFR STRATUS TO DEVELOP BY SUNRISE SUNDAY...ESPECIALLY ACROSS THE NORTH CAROLINA MOUNTAINS... WHERE FOG AND DRIZZLE IS LIKELY. MEDIUM TO HIGH CONFIDENCE IN CIGS THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN VSBYS THROUGH THE TAF VALID PERIOD. MEDIUM CONFIDENCE IN WIND DIR THROUGH THE TAF VALID PERIOD...HIGH CONFIDENCE IN WIND SPD THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... CLOUDS WILL LINGER...EVEN AFTER THE -RA ENDS SUNDAY...BUT OVERALL CONDITIONS SHOULD BE MOSTLY MVFR...WITH LESS IFR OR WORSE CIGS/VSBYS. BEYOND SUNDAY...BROAD UPPER TROUGH DEVELOPING ACROSS THE NORTHERN STATES...WITH THE RNK CWA ON THE SOUTHERN EDGE OF THIS BROAD UPPER TROUGH...LEADING TO PRIMARILY CONTINUED ZONAL FLOW. LATEST MODEL TRENDS BEGINNING TO FAVOR POTENTIAL CHANGE TO A MORE NW FLOW ALOFT AS THE WEEK PROGRESSES...WHICH SHOULD ATTEMPT TO PUSH THE PESKY DEEP MOISTURE FURTHER SOUTH AWAY FROM THE REGION. OVERALL...EXPECT MVFR CONDITIONS TO PERSIST INTO MONDAY AS AFOREMENTIONED UPPER TROUGH BRINGS MORE CLOUDS AND SHOWERS TO THE REGION. HOWEVER...THIS WILL NOT BE A WEDGE SETUP LIKE CURRENT SITUATION...SO OVERALL IMPROVED CONDITIONS EXPECTED COMPARED TO CURRENT. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...NF NEAR TERM...AMS/NF SHORT TERM...NF LONG TERM...JH AVIATION...NF/SK

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