Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 292006 AFDRNK AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BLACKSBURG VA 406 PM EDT SAT AUG 29 2015 .SYNOPSIS...
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A WEAK UPPER LEVEL DISTURBANCE WILL LIFT NORTH ALONG THE APPALACHIANS SUNDAY INTO MONDAY...BRINGING A GREATER CHANCE FOR SHOWERS AND A FEW THUNDERSTORMS TO THE REGION. UPPER LEVEL HIGH PRESSURE WILL THEN STRENGTHEN AND KEEP US IN A RATHER STAGNANT PATTERN...WITH A CHANCE FOR AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS THROUGH THE MIDDLE OF THE WEEK.
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&& .NEAR TERM /THROUGH SUNDAY/...
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AS OF 330 PM EDT SATURDAY... LATE AFTERNOON RADAR SHOWS THAT WIDELY SCATTERED SHOWERS HAVE DEVELOPED ALONG THE FAR WESTERN SLOPES OF THE APPALACHIANS. NOT MUCH IS EXPECTED FROM THIS ACTIVITY AND IT WILL FADE AWAY WITH THE LOSS OF HEATING THIS EVENING. HOWEVER THE CLOUDS WILL REMAIN TRAPPED UNDER THE SUBSIDENCE INVERSION AND ALLOW THE RESIDUAL CLOUDS TO LINGER THROUGH THE OVERNIGHT PERIOD AS HIGH CLOUDS CONTINUE TO STREAM NORTHWARD INTO THE REGION. THIS WILL MAKE FOR GENERALLY MOSTLY CLOUDY CONDITIONS AND HELP KEEP TEMPERATURES A BIT WARMER THAN RECENT NIGHTS. GENERALLY EXPECTING LOW TO MID 60S ACROSS THE PIEDMONT TO UPPER 50S/LOWER 60S WEST OF THE BLUE RIDGE. THERE MAY ALSO BE SOME FOG DEVELOPMENT IN THE VALLEYS WEST OF THE BLUE RIDGE FOR AREAS THAT MANAGE TO SEE ANY SUBSTANTIAL BREAKS IN THE CLOUDS. THEN AFTER SEVERAL DAYS OF LITTLE CHANGE IN THE SYNOPTIC PATTERN...A CLOSED LOW THAT HAS BEEN SPINNING OVER THE NORTHERN GULF OF MEXICO WILL BE OPENING UP AND THROWING SHORT WAVE ENERGY IN OUR DIRECTION TOMORROW. WATER VAPOR IMAGERY ALSO SHOWS EXCELLENT MOISTURE TRANSPORT FROM THE GULF WHICH WILL BOOST OUR PRECIPITABLE WATER VALUES INTO THE 1.0 TO 1.5 INCH RANGE. THIS WILL BE ENOUGH TO GENERATE A MORE WIDESPREAD CHANCE FOR SHOWERS/SLIGHT CHANCE FOR THUNDER ON SUNDAY WITH A LOCAL DOWNPOUR POSSIBLE. THERE REMAINS LITTLE IN THE WAY OF INSTABILITY OR SHEAR SO DO NOT SEE ANY THREAT OF SEVERE WEATHER. HIGHS TOMORROW WILL RANGE FROM THE MID/UPPER 80S EAST TO UPPER 70S/LOWER 80S WEST.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
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AS OF 355 PM EDT SATURDAY A PIECE OF THE UPPER TROF AND VORTICITY MAXIMUM TRACKS SLOWLY NORTH ACROSS THE SOUTHERN AND CENTRAL APPALACHIANS SUNDAY NIGHT. AT THE SAME TIME A WEAK SHORT WAVE TRACKING THE THE BASE OF AN UPPER TROF OVER NEW ENGLAND WILL CROSS THROUGH THE OHIO VALLEY. BY MONDAY EVENING THE MODELS HAVE THE UPPER TROF AXIS EAST OF THE FORECAST AREA. THE COMBINATIONS OF THE LIFT FROM THESE FEATURES WILL RESULT IN SHOWERS AND THUNDERSTORMS SUNDAY NIGHT AND MONDAY. MOISTURE BELOW 850 MB IS NOT AS HIGH AS WOULD BE OPTIMAL AND SURFACE/LOW LEVEL WINDS WILL NOT CONTRIBUTE TO LIFT OR MOISTURE ADVECTION. WILL HAVE A SMALL INCREASE IN PROBABILITY OF PRECIPITATION ON SUNDAY NIGHT AND MONDAY. 500 MB TEMPERATURES WILL COOL LATE SUNDAY NIGHT AND MONDAY MORNING BUT LIFTED INDEX VALUES AND HEATING WILL BE MEAGER ON MONDAY. CAPES AROUND 500 J/KG BUT ARE AT A RELATIVE MINIMUM OVER THE FORECAST AREA WITH HIGHER VALUES SURROUNDING US. KEPT PROBABILITY OF THUNDER AT SLIGHT CHANCE. PRECIPITABLE WATER VALUES AND DEW POINTS WILL BE SLOWLY INCREASING SUNDAY NIGHT AND MONDAY. THIS PLUS THE CLOUD COVER WILL LIMIT DROP IN MINIMUM TEMPERATURES ON SUNDAY NIGHT. CLOUDS AND ANY PRECIPITATION WILL HOLD DOWN RISE IN MAXIMUM TEMPERATURES ON MONDAY. LITTLE CHANGE NEEDED TO FORECAST FOR MONDAY NIGHT AND TUESDAY. PROBABILITY OF PRECIPITATION DECREASES AND TEMPERATURES WILL BE NEAR NORMAL. A MAJORITY ON THE DEEP MOISTURE WILL STAY JUST SOUTH AND SOUTHEAST OF THE FORECAST AREA.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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AS OF 255 PM EDT SATURDAY... LONG WAVE SYNOPTIC PATTERN THROUGH THE PERIOD KEEPS UPPER TROFING OVER THE PACIFIC NORTHWEST AND AN LARGE RIDGE OVER THE CENTRAL UNITED STATES. AT THE SURFACE A BROAD AREA OF HIGH PRESSURE WILL REMAIN OVER THE EASTERN UNITED STATES. MODELS NOT SHOWING ANY WELL DEFINED OR ORGANIZED SMALLER SCALE FEATURES THAT WILL TRIGGER SHOWERS AND THUNDERSTORMS THROUGH DAY 7. BULK OF SHOWERS AND THUNDERSTORMS WILL BE TYPICAL AFTERNOON AND EVENING OROGRAPHICALLY DRIVEN COVERAGE. STEERING FLOW WILL REMAIN RELATIVELY WEAK SO ANY STRONGER CELLS WILL HAVE THE POTENTIAL TO PRODUCE HEAVY RAIN. NO EXCEPTIONALLY WARM OR COOL TEMPERATURES THROUGH DAY 7.
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&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/... AS OF 150 PM EDT SATURDAY... SYNOPTIC PATTERN REMAINS UNCHANGED WITH SOME RIDGING ALOFT FROM THE EAST WITH HIGH PRESSURE AT THE SURFACE. THIS IS KEEPING THE REGION IN A LIGHT WIND ENVIRONMENT WITH A CHANCE FOR DIURNAL OROGRAPHICALLY INDUCED SHOWERS. SATELLITE IMAGES ARE SHOWING CU FIELD BLOOMING EARLY THIS AFTERNOON AS HIGHER CLOUDS RIDE UP OVER THE TOP FROM THE SOUTH. ANY SHOWER ACTIVITY WILL BE ISOLATED TO WIDELY SCATTERED SO WILL GENERALLY KEEP TAFS DRY AND ONLY USE VCSH AT KBLF/KLWB WHERE THE BEST CHANCE POPS ARE LOCATED DEEPER INTO THE TERRAIN. MODEL SOUNDINGS SHOW A GOOD AMOUNT OF MOISTURE IN THE COLUMN THROUGH THE PERIOD SO DIURNAL CLOUDS WILL BE IN NO GREAT HURRY TO DISSIPATE WITH THE LOSS OF HEATING. WITH THIS IN MIND...EXPECTING MULTILAYERED VFR CLOUDS AT ALL SITES THROUGH THIS TAF PERIOD. BELIEVE THE LOWEST CIGS WILL BE IN AND OUT FOR VARIOUS PERIODS OVERNIGHT BUT WITHOUT A CHANGE IN FLIGHT CATEGORY WILL KEEP TAFS AS SHORT AND SIMPLE AS POSSIBLE AND NOT INDICATE CHANGES IN VFR CIGS. THERE SHOULD BE ENOUGH RADIATIONAL COOLING TO ALLOW FOR SOME FOG FORMATION AGAIN TONIGHT PRIMARILY AT KBCB AND KLWB...BUT KBCB LOOKS TO BE AFFECTED BY MORE CLOUDINESS SO WILL USE A TEMPO FOR MVFR VSBY TOWARD DAYBREAK. KLWB WAS AN OVERACHIEVER LAST NIGHT AND WENT TO LIFR DESPITE SOME CLOUDS AROUND SO WILL GO WITH THIS TREND AGAIN FOR TONIGHT AND INDICATE LIFR CONDITIONS TOWARD DAYBREAK. ANY FOG DISSIPATED AFTER DAYBREAK SUNDAY AND IT LOOKS LIKE SHOWER ACTIVITY WILL BE MORE WIDESPREAD SUNDAY AFTERNOON AS A GOOD DOSE OF SHORT WAVE ENERGY RISES OUT OF THE GULF COAST AND INTO THE REGION. BELIEVE THE BEST CHANCES FOR PRECIPITATION WILL BE BEYOND THIS TAF PERIOD SO WILL ONLY INCLUDE VCSH AT KBLF/KLWB WHERE TERRAIN INFLUENCES MAY GET CONVECTION OFF TO AN EARLIER START. EXTENDED AVIATION DISCUSSION... SHORT WAVE ENERGY MOVING UP FROM THE SOUTH WILL SUPPORT AN INCREASED CHANCE FOR CONVECTIVE ACTIVITY INTO MONDAY. GENERALLY EXPECT THE BEST CHANCES FOR MVFR/IFR TO BE LATE NIGHT/EARLY MORNING DUE TO FOG AND STRATUS DEVELOPMENT FROM THE BLUE RIDGE WEST ESPECIALLY AT KLWB/KBCB. WILL THEN REMAIN IN A WEAKLY FORCED SYNOPTIC ENVIRONMENT THROUGH MIDWEEK WITH CHANCES FOR DIURNAL CONVECTION MAINLY FROM THE BLUE RIDGE WEST...AND SOME MVFR/IFR FOG/STRATUS DEVELOPMENT AT NIGHT ESPECIALLY AT KBCB AND KLWB. && .EQUIPMENT...
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AS OF 400 PM EDT SATURDAY... THE DEW POINT READING AT KJFZ...RICHLANDS VA AWOS...IS INCORRECT. AT THIS TIME WE DO NOT KNOW WHEN THIS SENSOR WILL BE REPAIRED.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...NONE. NC...NONE. WV...NONE. && $$ SYNOPSIS...AMS NEAR TERM...MBS SHORT TERM...AMS LONG TERM...AMS AVIATION...MBS/NF EQUIPMENT...AMS

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