Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 050857 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 457 AM EDT SAT SEP 5 2015 .SYNOPSIS...
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SOUTHEAST FLOW BRINGS A SUBTLE DECREASE IN HEAT...HUMIDITY AND THUNDERSTORM COVERAGE TODAY. WEAKENING MID LEVEL DISTURBANCES GRADUALLY GIVE WAY TO HIGH PRESSURE DURING THIS LABOR DAY WEEKEND.
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&& .NEAR TERM /THROUGH TONIGHT/...
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SFC HIGH PRESSURE BUILDS DOWN THE EAST COAST BEHIND A BACK DOOR COLD FRONT...BRINGING A SLIGHT LOWERING OF TEMPERATURES AND DEW POINTS FOR THE NEAR TERM. UPPER LEVEL FORCING WILL BE WEAK...IN LIGHT FLOW IN A COLL AREA BETWEEN UPPER LEVEL HIGHS TO THE E AND SW...AND UPPER LEVEL LOWS TO THE S AND N. AS SUCH...EXPECT AFTERNOON THUNDERSTORMS TO BE FEWER AND FARTHER BETWEEN COMPARED WITH FRI...AND THEY SHOULD DISSIPATE PROMPTLY UPON LOSS OF HEATING THIS EVENING. THE SE FLOW AROUND THE BACK SIDE OF THE E COAST HIGH WILL PROVIDE UPSLOPE FLOW ON THE EASTERN FRINGES OF THE FCST AREA. THIS MAY RESULT IN A LIGHT SHOWER THERE THIS MORNING...AND THEN MAY BE ENOUGH TO HELP INITIATE STORMS OVER THE MOUNTAINS THIS AFTERNOON ESPECIALLY IF WE COULD GET DIFFERENTIAL HEATING BETWEEN THE E AND W SLOPES. THESE STORMS MAY THEN DRIFT WWD OUT OF THE MOUNTAINS...IN THE LIGHT MEAN LAYER ERLY FLOW. ANOTHER TRANQUIL NT IS UPCOMING WITH VALLEY FOG FORMING..AS SFC HIGH PRESSURE RIDGING NOSES SWWD OVER THE AREA. MOS GUIDANCE IS WELL CONVERGED AND LOOKS GOOD IN THIS BENIGN PATTERN...LEANED TOWARD BIAS CORRECTED VALUES FOR LOWS TONIGHT.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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UPPER RIDGE HOLDS ACROSS EASTERN U.S. DURING THE PERIOD...WITH A CONTINUATION OF ABOVE NORMAL TEMPERATURES FOR THIS TIME OF YEAR. WEAK DISTURBANCES...COMBINED WITH A SOUTHEASTERLY FLOW AS SURFACE HIGH PRESSURE REMAINS CENTERED OFF THE COAST...WILL KEEP CHANCES OF SHOWERS AND STORMS IN THE FORECAST...MAINLY ACROSS THE MOUNTAINS...AND MAINLY DURING PEAK HEATING HOURS. COULD SEE AN ISOLATED STORM SNEAK DOWN INTO THE LOWLANDS...BUT FOR NOW WILL MAINTAIN A DRY FORECAST. RIDGE WILL START TO FLATTEN OUT ACROSS THE AREA LATE IN THE PERIOD...WITH THE APPROACH OF A COLD FRONT.
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&& .LONG TERM /TUESDAY THROUGH FRIDAY/... MORE OF THE SAME THROUGH WEDNESDAY...HOT AND MUGGY CONDITIONS WITH JUST AN ISOLATED SHRA/TSRA. PATTERN FINALLY BEGINS TO BREAK TOWARD THURSDAY WITH FALLING HEIGHTS AMID A TRANSITION MORE INTO A E CONUS TROF. THE COLD FRONT THAT WILL MARK THIS TRANSITION LOOKS TO CROSS LONG ABOUT THURSDAY WITH A GOOD SHOT A MUCH NEEDED RAIN OVER THE AREA. && .AVIATION /08Z SATURDAY THROUGH WEDNESDAY/... CONVECTION HAD DIED OFF FOR THE NT...AND DENSE VALLEY WAS FORMING BENEATH A CANOPY OF ONLY HIGH THIN CLOUD. THIS CIRRUS MAY BE JUST ENOUGH TO PREVENT A PERSISTENT LIFR DENSE FOG AT MOST AIRPORTS. BKW HAD EXPERIENCED IFR FOG IN THE WAKE OF A THUNDERSTORM THAT AFFECTED THAT AIRPORT 00-02Z. IT WAS LIFTING OUT AROUND 06Z AND IT WAS UNCLEAR WHETHER A LIGHT SE PUFF THERE WOULD BE ENOUGH TO KEEP THE FOG FROM RETURNING THERE OVERNIGHT. AMENDMENTS ARE LIKELY THERE. THE OVERALL VERY WARM AND HUMID WEATHER PATTERN CONTINUES...ALTHOUGH A SE FLOW OF SLIGHTLY DRIER AIR WILL BRING THE HUMIDITY DOWN A BIT ON SAT. SCATTERED CONVECTION SAT AFTERNOON MAY NOT AMOUNT TO AS MUCH AS WAS THE CASE FRI AFTERNOON. THIS CONVECTION SHOULD DIE OWN MORE PROMPTLY UPON SUNSET SAT EVENING...AND DENSE VALLEY FOG WILL START FORMING BY 06Z ALTHOUGH IT IS NOT LIKELY TO DIRECTLY IMPACT AIRPORTS UNTIL AFTER 06Z SUNDAY. HOWEVER...AT LEAST A PERIOD OF DENSE FOG IS LIKELY AFTER DARK WHERE IT RAINS SAT AFTERNOON AND EVENING. SFC FLOW WILL BE LIGHT S TO SE WHILE E TO NE FLOW ALOFT OVERNIGHT BECOMES LIGHT SE ON SAT. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z SUNDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: TIMING AND COVERAGE OF FOG OVERNIGHT TONIGHT MAY VARY FROM FORECAST. CONVECTION SAT AFTERNOON IS EXPECTED TO BE SCATTERED AND THUS NOT EXPLICITLY CODED UP IN THE TAFS...BUT AMENDMENTS MAY BE NEEDED AS THE AFTERNOON CONVECTION DEVELOPS AND EVOLVES. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE SAT 09/05/15 UTC 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 EDT 1HRLY 02 03 04 05 06 07 08 09 10 11 12 13 CRW CONSISTENCY H H H M M M H H H H H H HTS CONSISTENCY M M L L L L L M H H H H BKW CONSISTENCY M H H H H H M M M M M M EKN CONSISTENCY M L L L L L L L H H H H PKB CONSISTENCY H H H H M M M H H H H H CKB CONSISTENCY H H H H H M M H H H H H AFTER 06Z SUNDAY... IFR POSSIBLE IN VALLEY FOG OVERNIGHT INTO THE MORNING NEXT SEVERAL NTS. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...TRM/SL NEAR TERM...TRM SHORT TERM...SL LONG TERM...30 AVIATION...TRM

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