Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 161726 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 126 PM EDT TUE SEP 16 2014 .SYNOPSIS... BROAD HIGH PRESSURE BUILDS FROM THE WEST...AND STAYS IN CONTROL INTO THE WEEKEND. COLD FRONT POSSIBLY TOWARD THE END OF THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/...
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UPDATE... NO CHANGES THIS AFTERNOON. SLOW CLEARING TAKING PLACE AS THE BOUNDARY LAYER MIXES WITH LOWER DEWPOINTS ADVECTING IN FROM THE NORTH. PREVIOUS DISCUSSION... A BROAD HIGH PRESSURE APPROACHES FROM THE WEST TO PRODUCE A WEAK NORTHERLY FLOW TODAY...BECOMING WEAKER FROM THE NORTHEAST WEDNESDAY. MEANWHILE ALOFT...NEAR ZONAL FLOW IS NOTICED IN H5 CHARTS THROUGH WEDNESDAY. THEREFORE...EXPECT DRY AND COOL WEATHER THROUGH THE PERIOD. THE NEAR CALM FLOW AND MOSTLY CLEAR SKIES WILL ALLOW FOR DENSE FOG FORMATION DURING THE PREDAWN HOURS WEDNESDAY MORNING. USED THE NAMDNG5 WITH FEW ADJUSTMENTS FOR TEMPERATURES THROUGH THE PERIOD.
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&& .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... TRANQUIL WEATHER WILL PERSIST IN THE SHORT TERM WITH HIGH PRESSURE DOMINATING...WITH A GENERALLY DRY FORECAST THROUGHOUT. A COUPLE OF DISTURBANCES PUSH THROUGH NW FLOW ALOFT WED NIGHT AND AGAIN THU. HOWEVER...WITH VERY LITTLE LLVL MOISTURE TO WORK WITH AND A STOUT NEAR-ISOTHERMAL CAP IN PLACE IN AND AROUND 750MB...ONLY AN INCREASE IN FLAT CU IS EXPECTED ACROSS THE MOUNTAINS DURING THE DAY WED AND OVER THE SOUTHERN PART OF THE FORECAST AREA WED NIGHT INTO THU. THE ONLY CAVEAT TO THE COMPLETELY DRY FORECAST IN THE SHORT TERM MAY COME IN THE HIGHEST PEAKS OF THE EASTERN MTS WED AFTERNOON. LATEST NAM12 MODEL POINT SOUNDINGS INDICATE NEAR-SATURATED LOW LEVELS WITH A MOISTURE DEPTH AND/OR CONVECTIVE LAYER DEPTH OF ABOUT 4KFT-5KFT UNDERNEATH AFOREMENTIONED CAP AROUND 750MB...WITH A DECENT RIDGE TOP CONVERGENCE SIGNATURE. IN FACT...CONSENSUS OF LATEST SHORT-TERM NWP DEPICTS SOME QPF BTWN 18Z WED AND 00Z THU IN THAT GENERAL AREA AS WELL AS AT LEAST SLIGHT CHANCE POPS. HOWEVER...WITH PWATS OF ONLY AROUND 0.85IN AND WITH SUCH A SHALLOW MOISTURE DEPTH...BELIEVE THE POPS AND PARTICULARLY THE QPF AMOUNTS TO BE OVERDONE AND HAVE KEPT MEASURABLE POPS OUT OF THE FORECAST. DID ELECT TO INSERT A SLIGHT CHANCE OF A SPRINKLE WED AFTERNOON...AGAIN ON THE HIGHEST PEAKS MAINLY ABOVE 3KFT WITH THE POTENTIAL FOR A SPRINKLE OR TWO HERE. THE ONLY OTHER ADJUSTMENT WAS TO PUT THIS SAME GENERAL AREA IN SOLID PARTLY CLOUDY SKY COVER DURING THE AFTERNOON. VERY LITTLE CHANGE FROM PREV FCST REGARDING TEMPERATURES...WITH GENERAL LOWER 70S IN THE LOWLANDS AND UPPER 40S/LOWER 50S LOWLANDS. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... FOR FRIDAY AND SATURDAY...USED A BLEND OF THE GFS...ECMWF...GFS ENSEMBLE MEAN...AND ECMWF ENSEMBLE MEAN. THIS KEEPS THE AREA UNDER HIGH PRESSURE WITH TEMPERATURES SLOWLY MODERATING SOME. FOR SUNDAY INTO MONDAY...A COLD FRONT WILL PUSH THROUGH THE AREA. USED A BLEND OF THE GFS ENSEMBLE MEAN AND THE ECMWF ENSEMBLE MEAN FOR FRONTAL TIMING. && .AVIATION /17Z TUESDAY THROUGH SATURDAY/...
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STARTING TO SEE SOME MIXING IN THE LOWEST LEVELS WHERE THE LOW STRATUS HAS PERSISTED...COMBINED WITH SOME DRIER AIR MOVING IN FROM THE NORTH. THEREFORE...SHOULD LOSE THE BULK OF THE MVFR CEILINGS AFTER 19Z AND BEFORE 22Z AS THE SKY BEGINS TO SLOWLY CLEAR AS WE HEAD TOWARDS 00Z WEDNESDAY. INTO TONIGHT...EXPECT MAINLY CLEAR CONDITIONS...ALLOWING FOR EARLY DEVELOPMENT OF RIVER VALLEY FOG. DROP ALL LOCATIONS EXCEPT BKW TO LIFR CONDITIONS BEFORE 06Z. FOG MIXES OUT AFTER 13Z WEDNESDAY TO VFR. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z WEDNESDAY... FORECAST CONFIDENCE: MEDIUM TO HIGH. ALTERNATE SCENARIOS: CLEARING OF THE MVFR COULD VARY BY AN HOUR OR SO. TIMING OF FOG DEVELOPMENT TONIGHT COULD VARY. 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. UTC 1HRLY 18 19 20 21 22 23 00 01 02 03 04 05 EDT 1HRLY 14 15 16 17 18 19 20 21 22 23 00 01 CRW CONSISTENCY L M M M M M M M M M M L HTS CONSISTENCY H M M M M M M M H H H L BKW CONSISTENCY M M M M L L L L L L L L EKN CONSISTENCY H M M M M H H H H M L L PKB CONSISTENCY M M M M M M M H H H M L CKB CONSISTENCY M H H M H H H M M M M M AFTER 18Z WEDNESDAY... NO WIDESPREAD IFR EXPECTED AT THIS TIME.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...ARJ/50 NEAR TERM...ARJ/26 SHORT TERM...50 LONG TERM...RPY AVIATION...26

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