Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 210824 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 424 AM EDT SUN SEP 21 2014 .SYNOPSIS... LOW PRESSURE WAS OVER MICHIGAN WITH A COLD FRONT TRAILING INTO THE MID MISSISSIPPI VALLEY. THIS FRONT WILL MOVE EAST TODAY AND TONIGHT...AND WILL REACH THE EAST COAST BY MONDAY MORNING. MONDAY THROUGH THURSDAY...A LARGE HIGH PRESSURE SYSTEM WILL COVER MUCH OF THE EASTERN UNITED STATES. && .NEAR TERM /THROUGH TONIGHT/... AS OF 400 AM SUNDAY... SATELLITE PICTURES AND SURFACE OBSERVATIONS SHOWED THAT FOG HAD DEVELOPED IN THE NEW AND GREENBRIER RIVER VALLEYS THIS MORNING. THE FOG WILL LIFT SHORTLY AFTER SUNRISE. TIMING OF THE FRONT REMAINS SIMILAR IN THE GUIDANCE AS PAST FEW RUNS. BULK OF SHOWERS AND THUNDERSTORMS WILL COME THROUGH THE FORECAST AREA BETWEEN 2PM/18Z AND 8PM/00Z. AMOUNT OF INSTABILITY THIS AFTERNOON WILL DEPEND ON HOW MUCH HEATING THERE IS...HOW FAST THE CLOUDS ARRIVE FROM THE WEST. MODELS HAVE ENOUGH CAPE AND SURFACE HEATING TO SUPPORT THUNDERSTORMS. MODELS ALSO CONFINE A MAJORITY OF THE PRECIPITATION TO ALONG AND WEST OF THE BLUE RIDGE. THIS SEEMS REASONABLE WITH THE LOW LEVEL WINDS STARTING FROM THE NORTH THIS MORNING AND BACKING TO THE WEST AHEAD OF THE FRONT AS HIGH PRESSURE OVER THE AREA WEAKENS. THE FRONT COMES THROUGH THE FORECAST AREA BETWEEN 00Z/8PM AND 06Z/2AM. DECENT PRESSURE RISES BEHIND THE FRONT WITH 850 MB TEMPERATURES DROPPING TO AROUND +6 IN SOUTHEAST WEST VIRGINIA BY MONDAY MORNING. EXPECTING SOME LOW LEVEL MOISTURE IN THE WESTERN UPSLOPE AREA AFTER MIDNIGHT...BUT BUFKIT FORECAST SOUNDINGS SHOWED THE MOISTURE WILL BE SHALLOW. EAST OF THE BLUE RIDGE WILL CLEAR OUT LATE TONIGHT. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... AS OF 300 AM EDT SUNDAY... AN UPPER LEVEL TROUGH WILL PIVOT ACROSS THE REGION WITH NORTHWEST FLOW AND LOW LEVEL MOISTURE KEEPING CLOUDS BANKED UP AGAINST WESTERN SLOPES THROUGH MONDAY MORNING. ONCE THIS TROUGH AXIS TRACKS TO THE MID ATLANTIC COAST DURING THE AFTERNOON...DRY AIR WILL ERODE MOUNTAIN CLOUDS WITH CLEAR CONDITIONS CONTINUING THROUGH THE REST OF THE PERIOD. DOWNSLOPE FLOW IS EXPECTED EAST OF THE BLUE RIDGE TO KEEP CLEAR SKIES THROUGH THE ENTIRE PERIOD. FOLLOWING THE PASSING OF THE UPPER LEVEL TROUGH...A SURGE OF COOLER DRIER AIR WILL MOVE OVER THE AREA. DEW POINTS WILL DROP INTO THE 40S MONDAY AFTERNOON AND CONTINUE TO LOWER INTO THE 30S ACROSS THE MOUNTAINS MONDAY NIGHT. OVERNIGHT LOWS WILL RANGE FROM THE UPPER 30S IN MOUNTAIN VALLEYS TO THE UPPER 40S IN THE PIEDMONT. TEMPERATURES WILL RUN 5F-10F COOLER THAN NORMAL MONDAY AND TUESDAY AFTERNOON. ALSO MONDAY...PRESSURE RISES WILL BRING BREEZY AND GUSTY CONDITIONS TO THE AREA...ESPECIALLY ALONG THE BLUE RIDGE. GUSTS ALONG THE BLUE RIDGE COULD TOP OUT AT 30 MPH. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... AS OF 100 PM EDT SATURDAY... THE EXTENDED PERIOD IS DOMINATED BY A 1032MB SURFACE HIGH THAT STARTS IN SOUTHERN QUEBEC ON WEDNESDAY AND WILL SLOWLY DRIFT SOUTH OVER THE NE STATES BY SATURDAY. THE RESULT OF THIS WILL BE AN EASTERLY WEDGE FLOW THROUGH THE ENTIRE PERIOD. THERE IS SIGNIFICANT DIFFERENCES IN PLACEMENT OF A MID LEVEL CLOSED LOW BY THE GFS AND THE ECMWF TO OUR WEST...WHICH WILL IMPACT HOW MUCH MOISTURE CAN GET PULLED INTO THE REGION. AT THIS POINT TRENDED TOWARD HPC AND THE DRIER GFS SOLUTIONS AND KEPT JUST LOW CHANCE POPS ALONG AND EAST OF THE BLUE RIDGE FROM THURSDAY THROUGH THE END OF THE PERIOD. ANY PRECIP THAT DOES FALL WILL LIKELY BE JUST PATCHY DRIZZLE WITH LITTLE TO NO ACCUMULATION. WENT BELOW GUIDANCE FOR HIGH TEMPS AS THE MODELS ARE TYPICALLY TOO WARM WITH AN EASTERLY FLOW. EXPECT SURFACE HIGHS OF MID TO UPPER 60S ACROSS THE MOUNTAINS TO LOW 70S EAST OF THE BLUE RIDGE. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... AS OF 135 AM EDT SUNDAY... HIGH CLOUDS AROUND A LOW OFF THE CAROLINA COAST WILL REDUCE FOG DEVELOPMENT IN THE PIEDMONT OF VIRGINIA AND NORTH CAROLINA EARLY THIS MORNING. DID NOT INCLUDE FOG AT KDAN AND KLYH FOR THIS MORNING. SATELLITE PICTURES SHOWED A CLEAR SKY WEST OF THIS CIRRUS. FOG WAS ALREADY FORMING AT KLWB IN THE GREENBRIER RIVER VALLEY. LOW CONFIDENCE FOR HOW MUCH FOG WILL REDUCE THE VISIBILITY AT KBCB THIS MORNING. FOG WILL DISSIPATE AFTER DAYBREAK....BUT MOISTURE ADVANCING AHEAD OF AN APPROACHING COLD FRONT WILL BRING MOSTLY CLOUDY SKIES...WITH LOW END VFR CIGS BY LATE MORNING TO THE MOUNTAINS. SCATTERED SHOWERS WILL ALSO DEVELOP IN THE MOUNTAINS DURING THE AFTERNOON. LOW LEVEL WINDS INCREASE WITH THE APPROACHING FRONT...AND GUSTS 20-25KTS ARE POSSIBLE BY THIS AFTERNOON IN THE HIGHER ELEVATIONS. WINDS BECOME WEST TO NORTHWEST BEHIND THE FRONT TONIGHT. MODELS WERE SUGGESTING SOME LOW LEVEL MOISTURE WILL BANK UP AGAINST THE WESTERN SLOPS OF THE APPALACHIANS LATE TONIGHT. MVFR CEILINGS ARE POSSIBLE AT KBLF AND KLWB AFTER MIDNIGHT. EXTENDED AVIATION DISCUSSION... HIGH PRESSURE AND DRIER AIR IN THE REGION MONDAY THROUGH THURSDAY WILL RESULT IN MAINLY VFR CONDITIONS. RIVER VALLEY FOG WILL STILL BE POSSIBLE AT NIGHT. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...RCS LONG TERM...CF AVIATION...AMS/PH

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