Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 240803 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 256 AM EST WED DEC 24 2014 .SYNOPSIS... LOW PRESSURE MOVES WEST OF THE AREA AND BRINGS RAIN WEDNESDAY. COLD FRONT LATE WEDNESDAY WILL BRING GUSTY WINDS. CHRISTMAS DAY STARTS COLD...CLOUDY...AND WINDY. HIGH PRESSURE CHRISTMAS NIGHT INTO FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... 10 PM UPDATE... FCST ON TRACK. DID RAISE DEW POINTS AHEAD OF THE COLD FRONT WED. 715 PM UPDATE... ADJUSTED TO FASTER TIMING OF THE RAIN OVER THE MIDDLE OHIO VALLEY THIS EVENING. ADDED THUNDER TO HTS TRI-STATE AREA WED MORNING...WITH DEEPENING LOW PRESSURE PASSING TO THE W...AND STRONG EARLY MORNING LLJ. MADE SOME ADJUSTMENTS TO WIND GUSTS DURING THE ADVISORY WED...KEEPING THE GIST AND REASONING OF THE PREVIOUS FCST WHICH KEYS IN MAINLY ON THE STRONG COLD ADVECTION DIRECTLY BEHIND THE COLD FRONT... BUT WITH TIMING AND DETAIL ADJUSTMENTS. PREV DISCN... MODELS HAVE DEEPENING SURFACE LOW TRACKING NORTHWARD THRU CENTRAL KENTUCKY AND WESTERN OHIO LATER TONIGHT AND WEDNESDAY. ONCE THE SURFACE LOW GETS INTO NORTHERN OHIO LATER WEDNESDAY MORNING...IT WILL SWEEP A STRONG COLD FRONT EASTWARD ACROSS MUCH OF THE AREA WEDNESDAY AFTERNOON...REACHING THE MOUNTAINS LATE IN THE DAY. WE LIKE THE SLIGHTLY FASTER GFS WITH THE FRONT...GIVEN THE STRENGTHENING PRESSURE GRADIENT AROUND THE LOW. BUT FIRST...MODELS HAVE A BROAD AND DEEP MOIST SOUTHERLY FLOW AHEAD OF THE LOW...WITH NUMEROUS UPPER DISTURBANCES TRACKING OVER THE AREA. LOOKS LIKE WIDESPREAD SHOWERS WILL MOVE IN EARLY TONIGHT AND QUICKLY OVER OVERSPREAD THE AREA. THERE IS SOME QUESTION AS TO IF AND WHEN THIS BROAD SHIELD OF SHOWERS WILL END BEFORE THE COLD FRONT STARTS TO TRACK EASTWARD WEDNESDAY AFTERNOON...AS TRACKING OF EMBEDDED DISTURBANCES IN THE SOUTHERLY FLOW WILL BE VERY DIFFICULT. PAST EXPERIENCE HAS SHOWN WITH THESE SYSTEMS THAT THERE WILL BE A TAPERING OFF OF THE SHOWERS BEFORE THE ORGANIZED BAND OF SHOWERS AND A FEW THUNDERSTORMS MOVE IN FROM THE WEST. THUS...WILL BRING IN CAT POPS TONIGHT...EXCEPT LIKELY IN THE SHADOW ZONE BETWEEN THE OHIO RIVER AND THE MOUNTAINS DUE TO SOUTHEAST DOWNSLOPING WINDS...AND THEN GO CHANCE POPS FROM SOUTH TO NORTH WEDNESDAY MORNING. EXPECT WELL ABOVE NORMAL TEMPS TONIGHT WITH SOUTHERLY FLOW AND CLOUDS. FOR WEDNESDAY...WILL TRACK THE STRONG COLD AND ORGANIZED BAND OF SHOWERS AND STORMS ACROSS THE AREA...REACHING THE OHIO RIVER AROUND 19Z...CENTRAL WV AROUND 21Z...AND ON INTO THE MOUNTAINS BY 00Z. WHILE THE WESTERLY 850MB WINDS ARE NOT PARTICULARLY IMPRESSIVE COMING IN BEHIND THE FRONT...THERE IS A REAL STRONG POTENTIAL FOR DOWNWARD MOMENTUM WITH A VERY IMPRESSIVE COLD ADVECTION SURGE. THIS IN COMBINATION WITH THE SHOWERS AND STORMS...POSE REAL THREAT FOR DAMAGING WINDS UP TO 50 MPH ALONG AND JUST BEHIND THE FRONT...SO THAT A WIND ADVISORY HAS BEEN POSTED FOR EXTREME SOUTHEAST OHIO...EXTREME NORTHEAST KENTUCKY AND EASTWARD INTO CENTRAL WEST VIRGINIA WEDNESDAY AFTERNOON. TEMPERATURES WILL BE WELL ABOVE NORMAL TONIGHT AND WEDNESDAY AHEAD OF THE FRONT...BEFORE FALLING OFF. SINCE THE COLD ADVECTION BEGINS LATER WEDNESDAY AFTERNOON...HAVE CHOSEN NOT TO GO WITH A NON DIURNAL TEMPERATURE CURVE. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... MODELS CONTINUE TO SHOW THAT 850 MB TEMPERATURES BEHIND THE FRONT ARE MARGINAL FOR AUTO CONVECTION...ALTHOUGH PLENTY OF LOW LEVEL MOISTURE AND UPSLOPE WINDS EXIST. THEREFORE...WILL KEEP POPS IN THE CHANCE CATEGORY. HIGH PRESSURE BUILDS IN FOR THURSDAY NIGHT AND FRIDAY. LOTS OF SPREAD IN THE ARRIVAL OF THE NEXT SYSTEM OVER THE WEEKEND. THE GENERAL TREND IS SLOWER HOWEVER...SO WILL REMOVE POPS FOR FRIDAY NIGHT. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... HIGH PRESSURE EXITING TO THE EAST EARLY IN THE LONG TERM. MODELS THEN HAVE SOME DISCREPANCIES GOING FORWARD. ECMWF HAS HAD A STRETCH OF RATHER LACKLUSTER PERFORMANCE IN THE LONG TERM RECENTLY...SO WHILE NOT DISCOUNTING IT COMPLETELY...DID PUT MORE WEIGHT ON THE GFS WHILE BLENDING. THIS BRINGS A MOISTURE STARVED COLD FRONT THROUGH SATURDAY...AND THEN A SECOND SURFACE WAVE RIDES UP THE FRONT SUNDAY INTO MONDAY. GFS HAS THIS WELL SOUTH AND EAST OF CWA...WITH THE EASTERN THIRD OF THE CWA BEING CLIPPED BY THE NW FRINGE OF THE QPF FIELD. FOR COMPARISON...THE ECMWF IS MUCH FARTHER WEST WITH THE SECOND WAVE. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... WIDESPREAD MVFR CONDITIONS...BECOMING MOSTLY IFR OVER THE WV MOUNTAINS TOWARD MORNING WITH AREA OF MOISTURE IN PLACE. DEVELOPING SURFACE LOW WILL MOVE NORTH FROM TN RIVER VALLEY INTO CENTRAL MI BY 00Z. IN RESPONSE SURFACE GRADIENTS WILL TIGHTEN AND COLD FRONT PASSAGE WILL TAKE PLACE LATE THIS AFTERNOON. WITH SOME DRY SLOTTING THIS AFTERNOON AHEAD OF THE FRONT IMPROVED CIG AND VISBY VALUES SLIGHTLY FROM MORNING VALUES. THEN EXPECT A ROUND OF GUSTY SHOWERS AND ISOLD TO SCT THUNDERSTORMS WITH THE COLD FRONT. SFC WINDS TO INCREASE TO 20KTS OR GREATER THIS AFTERNOON WITH 30KTS LIKELY ON THE RIDGETOPS. A FEW STRONGER GUSTS CAN BE EXPECTED WITH ANY CONVECTION INVOF FRONT AS IT TRACKS THROUGH...REACHING THE CRW-PKB LINE BY ABOUT 00Z. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z THURSDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: IFR CONDITIONS MAY BE MORE WIDESPREAD THIS MORNING IN AREAS OF HEAVIER RAIN AND FOG. TIMING OF CHANGING CONDITIONS WITH THE DRY SLOT AND THEN THE COLD FRONT MAY VARY THIS AFTERNOON. 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 WED 12/24/14 UTC 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 EST 1HRLY 01 02 03 04 05 06 07 08 09 10 11 12 CRW CONSISTENCY H H M M H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY M M M M M M H M H H H M EKN CONSISTENCY M H H L H H L H H H H H PKB CONSISTENCY M M M H H M M H H H H H CKB CONSISTENCY H H M H H H H H H H H H AFTER 06Z THURSDAY... IFR IN CLOUDS POSSIBLE IN THE HIGHER ELEVATIONS OF THE MOUNTAINS WED NT INTO THU. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...WIND ADVISORY FROM NOON TODAY TO 10 PM EST THIS EVENING FOR WVZ005>011-013>019-024>026. OH...WIND ADVISORY FROM NOON TODAY TO 10 PM EST THIS EVENING FOR OHZ066-067-075-076-083>087. KY...WIND ADVISORY FROM NOON TODAY TO 10 PM EST THIS EVENING FOR KYZ101>103-105. VA...NONE. && $$ SYNOPSIS...TRM/RPY/JMV/MZ NEAR TERM...TRM/JMV SHORT TERM...RPY LONG TERM...MZ AVIATION...KMC

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