Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 210540 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 140 AM EDT SUN SEP 21 2014 .SYNOPSIS... HIGH PRESSURE TO OUR NORTH WILL SLIDE EAST TONIGHT AS LOW PRESSURE OFF THE SOUTHEAST COAST LIFTS NORTH TO JUST OFF THE NORTH CAROLINA COAST BY SUNDAY MORNING. A COLD FRONT WILL MOVE EAST ACROSS OUR REGION SUNDAY INTO SUNDAY NIGHT AS LOW PRESSURE MOVES UP THE ATLANTIC OCEAN. MONDAY THROUGH THURSDAY...A LARGE HIGH PRESSURE SYSTEM WILL COVER MUCH OF THE EASTERN UNITED STATES. && .NEAR TERM /THROUGH TODAY/... AS OF 1015 PM EDT SATURDAY... FORECAST ON TRACK. HIGH CLOUDS STREAMING NORTH ASSOCIATED WITH LOW PRESSURE ALONG THE SOUTHEAST ATLANTIC COAST. GSO EVENING SOUNDING INDICATED THIS CLOUD LAYER WAS BETWEEN 35-40KFT AGL OR 200-260 MB. MODELS KEEP THIS MOISTURE PINNED MAINLY TO COAST JUST BRUSHING OUR EASTERN CWA...WITH LYH/MTV/GSO AND POINTS EAST BECOMING OVC AT TIMES OVERNIGHT FROM THIS HIGHER LAYER OF CLOUD. LOOKING WEST... CLOUDS WERE ALSO APPROACHING FROM THE OHIO VALLEY...THIS CLOUD COVER WAS ASSOCIATED WITH AN UPPER TROUGH OVER THE GREAT LAKES. THE UPPER TROUGH OVR THE GREAT LAKES REGION WILL DEEPEN AND TRAVEL EAST TOWARD NEW ENGLAND ON SUNDAY. SFC HIGH PRESSURE WILL SLIDE EAST TONIGHT...AS LOW PRESSURE OF THE GEORGIA COAST LIFTS NORTHWARD IN THE ATLANTIC OCEAN. HIGH LEVEL CLOUDS WILL SPREAD NORTHWARD AHEAD OF THE SOUTHEAST LOW CENTER TONIGHT. ADDED THE MENTION OF PATCHY FOG OVERNIGHT. WENT WITH LOW TEMPERATURES CLOSE TO THE ADJMAVBC WITH READINGS FROM THE LOWER 50S IN THE COOLER VALLEYS TO NEAR 60 IN THE PIEDMONT. A COLD FRONT WILL MOVE ACROSS THE REGION SUNDAY INTO SUNDAY NIGHT. THIS STRONG FRONTAL BOUNDARY WILL BE PUSHED BY AN UPPER LEVEL TROUGH TRACKING OVER THE GREAT LAKES. THE FRONT AND ASSOCIATED CONVECTION IS EXPECTED TO APPROACH THE AREA SUNDAY AFTERNOON...TRAVEL ACROSS THE MOUNTAINS SUNDAY EVENING AND EXIT THE PIEDMONT SUNDAY NIGHT. WITH THE STRONG MIDLEVEL FLOW AT 700 MB AS THE UPPER TROUGH DEEPEN AND SOME INSTABILITY...SPC IN THE DAY 2 CONVECTIVE OUTLOOK HAS ALLOWED FOR A 5 PERCENT CHANCE OF AN ISOLATED STRONG THUNDERSTORM WITH GUSTY WINDS BEING THE MAIN THREAT FOR SUNDAY AFTERNOON. LEANED HIGH TEMPERATURES SUNDAY CLOSE TO ADJMETBC WITH VALUES FROM THE MID 70S IN THE MOUNTAINS TO THE MID 80S IN THE PIEDMONT. && .SHORT TERM /TONIGHT THROUGH TUESDAY/... AS OF 330 PM EDT SATURDAY... THE COLD FRONT WILL ENTER OUR SOUTHEAST WEST VIRGINIA COUNTIES SHORTLY BEFORE MIDNIGHT SUNDAY EVENING...AND WILL CONTINUE RAPIDLY SOUTHEAST...EXITING THE SOUTHSIDE BY AROUND 6 AM MONDAY MORNING. THE FRONT WILL BRING WITH IT A NORTHWESTERLY WIND SHIFT THAT WILL USHER IN COOLER AND DRIER CANADIAN AIR...DEFINITELY A SIGNAL THAT AUTUMN IS COMING AS WE APPROACH THE EQUINOX. DRIER AIR WILL CAUSE A RAPID REDUCTION IN SHOWER ACTIVITY DURING THE OVERNIGHT HOURS...WITH ONLY A FEW SPRINKLES REMAINING ACROSS OUR NORTHWEST FLOW UPSLOPE REGIONS IN SOUTHEAST WEST VIRGINIA BY DAWN. HIGH PRESSURE WILL BUILD INTO THE AREA ON MONDAY ON A 4MB TO 5MB PRESSURE GRADIENT...RESULTING IN GUSTY NORTHWEST WINDS REACHING 20 MPH TO OCCASIONALLY 25 MPH AT TIMES ALONG THE HIGHER RIDGES. GUSTS ACROSS THE PIEDMONT WILL BE LOWER...GENERALLY AROUND 15 MPH. WIND SPEEDS WILL DIMINISH DURING EARLY EVENING AS THE CENTER OF HIGH PRESSURE SINKS SOUTH OF THE GREAT LAKES TOWARD THE OHIO RIVER VALLEY. HIGH PRESSURE WILL REMAIN THE DOMINANT FEATURE OF OUR WEATHER THROUGH TUESDAY NIGHT...GRADUALLY PUSHING TOWARD NEW ENGLAND TO BRING OUR WINDS INCREASINGLY NORTHEASTERLY. WITH CLEAR SKIES EXPECTED MONDAY THROUGH TUESDAY NIGHT...AFTERNOON HIGHS WILL RANGE FROM THE MID 60S ACROSS THE MOUNTAINS TO THE MID 70S ACROSS THE PIEDMONT. OVERNIGHT LOWS WILL FALL INTO 40S...POSSIBLY INTO THE UPPER 30S IN A FEW OF THE DEEPER MOUNTAIN VALLEYS MONDAY NIGHT. && .LONG TERM /TUESDAY NIGHT 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 /06Z SUNDAY THROUGH THURSDAY/...
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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.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS/KK NEAR TERM...KK/PM SHORT TERM...NF LONG TERM...CF AVIATION...AMS/PH

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