Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 290007 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 807 PM EDT SUN SEP 28 2014 .SYNOPSIS... HIGH PRESSURE CENTERED JUST NORTH OF THE REGION WILL WEAKEN TONIGHT. LOW PRESSURE DEVELOPING ALONG THE CENTRAL GULF COAST WILL MOVE NORTHEAST TONIGHT INTO MONDAY...BRINGING WIDESPREAD CLOUD COVER AND A PERIOD OF LIGHT RAIN. FOR OUR REGION RAINFALL FROM THIS SYSTEM IS EXPECTED TO BE LESS THAN A QUARTER OF AN INCH. THE HEAVIER RAINS WILL FALL TO OUR SOUTH. && .NEAR TERM /THROUGH MONDAY/...
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AS OF 345 PM EDT SUNDAY... HIGH PRESSURE CENTERED JUST NORTH OF OUR REGION WILL WEAKEN TONIGHT. THIS WILL ALLOW DEEPER MOISTURE TO START FLOWING NORTHWARD IN ADVANCE OF A DEVELOPING STORM SYSTEM ALONG THE CENTRAL GULF COAST. A STATIONARY FRONT WHICH HAS BEEN OVER THE GULF OF MEXICO THE LAST COUPLE OF DAYS WILL BE THE FOCUS FOR DEVELOPING LOW PRESSURE...THIS LOW TAKING SHAPE OVER THE WESTERN PANHANDLE OF FLORIDA MONDAY. MODELS ARE IN AGREEMENT THIS SURFACE LOW WILL TRACK EAST-NORTHEAST PASSING OFF THE FLORIDA/GEORGIA COAST MONDAY NIGHT...AND NEVER GAINING MUCH LATITUDE. AS SUCH...FOR OUR FORECAST AREA THIS MEANS LESS RAINFALL THAN ANTICIPATED WITH AN OVERALL DOWNWARD TREND IN QPF COMPARED TO PREVIOUS FORECASTS. STILL THINK THERE WILL BE AN OPPORTUNITY FOR LIGHT RAIN MONDAY...JUST NOT A LOT OF QPF...GENERALLY A TENTH OF AN INCH OR LESS ON THE AVERAGE. FOR TONIGHT...CLOUDS WILL CONTINUE TO INCREASE AND THICKEN AS THE STORM SYSTEM GETS MORE ORGANIZED ALONG THE GULF COAST. DEEPER MOISTURE WILL BE FLOWING NORTH WITH TIME...RAIN OVERSPREADING THE SOUTHEAST STATES DURING THE OVERNIGHT. THE WEDGE OF DRY AIR WHICH HAS BEEN DRIVEN DOWN THE EAST SIDE OF THE APPALACHIANS WILL LIKELY RESULT IN A FORK SHAPE TO THE DEVELOPING PRECIPITATION FIELD WITH RAIN DEVELOPING TO OUR WEST UP THROUGH THE TENNESSEE VALLEY...AND RAIN DEVELOPING TO OUR SOUTHEAST UP THROUGH THE PIEDMONT. BY DAYBREAK MONDAY...EXPECTATION IS FOR LIGHT RAIN TO BE MOVING INTO OUR FAR WESTERN CWA...BUT FADING AS IT PASSES OVER THE MOUNTAINS INTO THE LOW LEVEL DRY AIR. FOR THE DAY MONDAY...A BRIEF PERIOD OF SATURATION OF THE LOW LEVELS PROVIDING A PERIOD OF LIGHT RAIN TO THE AREA. THE HEAVIER RAINS WILL BE SKIRTING OUR REGION TO THE SOUTH...THE DEEPER MOISTURE MOVING FROM THE GULF COAST TO ALONG THE SOUTHEAST ATLANTIC BEACHES MONDAY NIGHT. GENERALLY FOLLOWED MOS TEMPS TONIGHT...BUT UNDERCUT THE HIGH TEMPERATURES MONDAY DUE TO DENSE CLOUD COVER. COOLEST READINGS TONIGHT WILL BE IN THE WV/VA HIGHLAND VALLEYS WHERE LOWS MAY DIP INTO THE LOWER 50S. UPPER 50S TO LOWER 60S ARE EXPECTED ELSEWHERE. MONDAYS HIGHS WILL LIKELY RANGE FROM THE UPPER 60S MOUNTAINS...TO LOWER 70S PIEDMONT.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... AS OF 345 PM EDT SUNDAY... SOME DRAMATIC CHANGES WITH THE 12Z MODELS COMPARED TO 24 HOURS AGO. MODELS HAVE LEANED TOWARDS THE GFS SOLUTION FOR MONDAY-MONDAY NIGHT WITH HEAVY RAIN POTENTIAL REMAINING SOUTH IN THE CAROLINAS. MODELS ARE TRACKING THE GULF DISTURBANCE EAST INSTEAD OF NORTHEAST AS A WEAK UPPER LEVEL TROUGH IS NOW FOLDED OVER THE NORTHERN MID ATLANTIC REGION SOUTH INTO THE TENNESSEE VALLEY. ALSO OVER THE FORECAST AREA IS A WEAK AREA OF HIGH PRESSURE WITH A WEDGE BOUNDARY CLOSER TO THE NC/SC BORDER. CONVECTION ALONG THIS BOUNDARY WILL MOVE EAST WHILE FLOW ALOFT IS RELATIVELY WEAK FURTHER LIMITING MOISTURE FROM ADVANCING NORTH. POPS FOR MEASURABLE RAINFALL ARE STILL VALID BUT THE AMOUNT AND DURATION OF RAIN WILL BE GREATLY REDUCE MONDAY NIGHT INTO TUESDAY MORNING. FROM TUESDAY INTO WEDNESDAY NIGHT...MODELS HAVE LEANED IN THE DIRECTION OF THE EURO...TRACKING A CLOSED LOW FROM THE GREAT LAKES TO OFF THE NEW ENGLAND COAST. THIS NORTHERN STREAM CLOSED LOW WILL PHASE WITH THE SOUTHERN STREAM GULF DISTURBANCE WEDNESDAY NIGHT...WELL OFF THE EAST COAST. SINCE BULK OF THE MOISTURE WILL BE WRAPPED CLOSE TO EACH LOW...RAIN CHANCE OVER THE FORECAST AREA ARE LOW. HOWEVER...MOISTURE WILL REMAIN ABUNDANT WITH A THETA-E RIDGE OVER THE REGION. LOW CLOUDS LIKELY TO REMAIN OVER THE AREA AND AS WINDS TURN TO THE EAST AS ANOTHER WEDGE OF HIGH PRESSURE BUILDS SOUTH...LIGHT RAIN/DRIZZLE IS POSSIBLE ALONG AND EAST OF THE BLUE RIDGE WEDNESDAY NIGHT INTO THURSDAY. DRIER WEATHER MEANS WARMER AFTERNOON TEMPERATURES. SINCE THE MODELS ARE KEEPING A WEDGE/EASTERLY FLOW IN THE AREA...BELIEVE MOS TEMPERATURES ARE TOO WARM. BOTH TUESDAY AND WEDNESDAY AFTERNOON...THE AREA SHOULD SEE UNIFORM TEMPERATURES IN THE 70S...JUST AT OR SLIGHT WARMER THAN NORMAL. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 345 PM EDT SUNDAY... SURFACE HIGH PRESSURE AND EASTERLY FLOW WILL REMAIN OVER THE REGION THURSDAY INTO FRIDAY MORNING. AN AXIS OF HIGH PRESSURE ALOFT MAY HELP SCOUR CLOUDS THURSDAY AFTERNOON AND EVENING...BEFORE THEY SPREAD BACK IN THURSDAY NIGHT. WITH AN EASTERLY FLOW AND MOISTURE...AREAS OF DRIZZLE AND/OR FOG IS POSSIBLE INTO FRIDAY MORNING. THE WEDGE WILL ERODE AND BREAK THROUGH THE DAY FRIDAY AS A COLD FRONT APPROACHES THE AREA LATE FRIDAY. PREFRONTAL SHOWERS WILL ENTER THE MOUNTAINS FRIDAY AFTERNOON THEN MOVE EAST OF THE BLUE RIDGE FRIDAY EVENING. MAJORITY OF THE RAIN /0.25/ WILL FALL OVER THE MOUNTAINS WITH LIGHTER AMOUNTS /0.10/ EAST OF THE BLUE RIDGE. WE DO EXPECTED SHOWERS TO ADVANCE EAST OF THE BLUE RIDGE AS WINDS BACK TO THE SOUTH AHEAD OF THE FRONT. INSTABILITIES ARE NOT LOOKING STRONG...THEREFORE MOSTLY SHOWERS WITH A FEW RUMBLES OF THUNDER FROM ELEVATED CONVECTION WITH THE FRONTAL PASSAGE. MODELS ARE ALSO MOVING THIS FRONT FASTER ACROSS THE REGION...CLEARING THE PIEDMONT BY EARLY SATURDAY MORNING. A STRAY MOUNTAIN SHOWERS IS POSSIBLE SATURDAY AFTERNOON AS AN UPPER LEVEL TROUGH/SHORT WAVE PIVOT ACROSS THE SOUTHERN OHIO VALLEY. WITH LITTLE TO NO GREAT LAKES TRAJECTORY...WE WILL JUST CALL SATURDAY A RAIN FREE DAY. HIGH PRESSURE BUILDS IN FROM THE SOUTHWEST SUNDAY. A WEAK PRESSURE GRADIENT WILL BRING BREEZY AND GUSTY CONDITIONS TO THE AREA OVER THE WEEKEND. SEASONAL TEMPERATURES THURSDAY WILL WARM ABOVE NORMAL ON FRIDAY...AHEAD OF THE COLD FRONT. ONCE THE FRONT PASSES EAST...SATURDAY AND SUNDAY HIGHS WILL RUN 5F-10F COOLER THAN NORMAL. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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AS OF 800 PM EDT SUNDAY... VFR CONDITIONS EXPECTED THROUGH MUCH OF THE TAF VALID PERIOD UNTIL DEEPER MOISTURE SPREADS NORTHEAST FROM DEVELOPING LOW PRESSURE AREA ALONG THE GULF COAST. SUNDAY NIGHT...EXPECT CEILINGS STARTING AT OR ABOVE 15 KFT ACROSS THE REGION THAT WILL LOWER AND THICKEN...BUT WILL REMAIN VFR THROUGH SUNRISE MOST LOCATIONS. THE EXCEPTION MAY BE FOR LOCATIONS SOUTH AND WEST OF BLF-BCB DURING THE 08Z-12Z TIME FRAME...WHERE PATCHY MVFR CEILINGS MAY DEVELOP AGAINST THE HIGHER TERRAIN. ON THE OTHER HAND...OVERCAST CONDITIONS ARE EXPECTED TO PREVENT DEVELOPMENT OF RADIATIONAL FOG MONDAY MORNING. A FEW POCKETS OF LIGHT RAIN MAY PASS ACROSS THE AREA OVERNIGHT...BUT ARE NOT EXPECTED TO IMPACT VISIBILITIES. LATEST MODELS HAVE TRENDED DRIER FOR THE FORECAST REGION...WITH THE GULF COAST LOW PRESSURE SYSTEM TAKING A MORE EASTWARD TRACK AS OPPOSED TO NORTHEASTWARD. THUS...THE MORE STEADY WIDESPREAD -RA IS NOW EXPECTED TO BE SLOWER TO ENTER THE REGION AND MAY NOT REACH ANY OF THE TAF SITES UNTIL AFTER 12Z/8AM MONDAY. WINDS WILL REMAIN LIGHT AND VARIABLE THROUGH THE PERIOD. HIGH CONFIDENCE IN CEILINGS THROUGH 12Z MONDAY...THEN MEDIUM CONFIDENCE. MEDIUM TO HIGH CONFIDENCE IN VISIBILITIES THROUGH THE TAF VALID PERIOD. MEDIUM TO HIGH CONFIDENCE IN WIND SPEED...LOW CONFIDENCE IN WIND DIRECTION THROUGH THE TAF VALID PERIOD. EXTENDED AVIATION DISCUSSION... A PERIOD OF SUB-VFR CONDITIONS IS ANTICIPATED LATE MONDAY AS THE GULF COAST DISTURBANCE TRACKS JUST SOUTH OF THE REGION. MVFR CEILINGS CAN BE EXPECTED ACROSS MUCH OF THE REGION MONDAY NIGHT. SOME IMPROVEMENT CAN BE EXPECTED TUESDAY-WEDNESDAY...BUT THERE IS ALSO GOOD POTENTIAL FOR LOW LEVEL EASTERLY WIND FLOW TO PERSIST OFF OF THE ATLANTIC OCEAN IN THE WAKE OF THE EARLY WEEK SYSTEM...PROMOTING CONTINUATION OF LOW CEILINGS/VISIBILITIES IN STRATUS. A STRONG COLD FRONT IS PROGGED TO MOVE THROUGH THE REGION LATE IN THE WEEK WITH A GOOD CHANCE OF SHOWERS AND COOLER WEATHER...BUT UNTIL THAT TAKES PLACE...WE MAY BE LOOKING AT AN EXTENDED PERIOD OF FAIRLY POOR AVIATION CONDITIONS DURING THE WEEK.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...PM NEAR TERM...PM SHORT TERM...RCS LONG TERM...RCS AVIATION...NF/PM

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