Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 210200 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 1000 PM EDT MON APR 20 2015 .SYNOPSIS... A COLD FRONT EXITING EAST...AS A LARGE LOW PRESSURE SYSTEM MOVES NORTH INTO CENTRAL CANADA. ANOTHER COLD FRONT CROSSES WEDNESDAY NIGHT INTO THURSDAY. COOLER WEATHER REMINDER OF THE WEEK. && .NEAR TERM /THROUGH TUESDAY/... 1000 PM UPDATE...COLD FRONT IS THROUGH THE CWA. STILL SOME LINGERING ISOLATED TO SCATTERED SHOWERS IN WV/VA COUNTIES. THOSE WILL GRADUALLY DIMINISH AND HEAD EAST INTO TONIGHT. NO SIGNIFICANT CHANGES MADE TO PREVIOUS FORECAST. PREVIOUS DISCUSSION... SURFACE COLD FRONT JUST STARTING TO APPROACH WESTERN PORTION OF THE FORECAST AREA...AND WILL TRACK EAST THROUGH THE EARLY EVENING HOURS WITH ASSOCIATED CONVECTIVE ACTIVITY. SEEING SOME ENHANCEMENT OF CU FIELD IN VISIBLE SAT IMAGERY INVOF OF FRONT WITH CONVECTION BEGINNING TO SHOW ONLY THE SLIGHTEST SIGN OF GAINING SOME LINEARITY IN ITS STRUCTURE. ATMOSPHERE IS ONLY MARGINALLY UNSTABLE AHEAD OF FRONT ACROSS WV AND SW VA. SFC DEWPOINTS INDICATED CONSIDERABLE MIXING OF THE LOWER BOUNDARY LAYER HAS OCCURRED OVER A BROAD SWATH OF WV. THUS...WE EXPECT A FAIRLY SLOW DEVELOPMENT PHASE TO CONVECTION ACROSS THE WESTERN PORTION EARLY THIS AFTERNOON...WITH MORE ENHANCED ACTIVITY LATE THIS AFTERNOON AND EARLY EVENING ACROSS THE FAR EASTERN MOUNTAINS. FRONT EXITS TONIGHT AND ATMOSPHERIC COLUMN WILL SEE A DRYING TREND WITH COOLER TEMPS. STARTED WITH INHERITED TEMP VALUES AND BLENDED IN MINOR TWEAKS. GUSTY WINDS CONTINUE INTO TUESDAY. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... MODELS SHOW AN ELONGATED MID LEVEL WAVE PASSING TO OUR WV/PA BORDER TUESDAY NIGHT. AT THE SFC...THE NAM SHOWS A COMPACTED CLOSED LOW MOVING ACROSS THE OH VALLEY...NORTHEAST INTO PA. ITS ASSOCIATED COLD FRONT COULD BRING RAIN SHOWERS...MORE PREVALENT OVER THE NORTHERN SECTIONS. THE CMC AND GFS JOINT THIS SOLUTION IN THEIR QPF FIELDS. THEREFORE...INCREASE POPS TO LIKELY DURING THE PREDAWN HOURS WEDNESDAY WITH MORE COVERAGE ACROSS THE NORTHERN COUNTIES THROUGH WEDNESDAY AFTERNOON. MODELS SHOW LIMITED THERMODYNAMIC INSTABILITY AND HIGH DEEP LAYERED SHEAR. HOWEVER...DO TO THE TIME OF THE FRONTAL PASSAGE AND THE WEAKNESS OF THIS FEATURE...KEEP THUNDER MENTION OUT FROM FORECAST FOR NOW. THE FRONT WILL PUSH ALL SHOWERS EAST SOUTHEAST BY WEDNESDAY EVENING. MODELS SHOW H850 FREEZING LEVEL CROSSING THE AREA FROM NORTHWEST TO SOUTHEAST. THEREFORE...EXPECT TEMPERATURES TO DROP INTO THE MID TO UPPER 50S LOWLANDS...RANGING INTO THE MID 40S HIGHER ELEVATIONS. COLD AIR ADVECTION CONTINUES WEDNESDAY NIGHT PERHAPS BRINGING SOME FROST MAINLY NORTHERN AND HIGHER ELEVATIONS AREAS. DRIER CONDITIONS EXPECTED ON THURSDAY AS A DRIER AIR MASS REMAINS IN PLACE. WENT CLOSER TO THE MOS CONSENSUS ALL WITH SOME TWEAKS THROUGH THE PERIOD. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... STILL A FAST WNW STEERING FLOW AROUND THE LARGE CIRCULATION OVER EASTERN CANADA AND NEW ENGLAND. SO TEMPERATURES WELL BELOW NORMAL THRU PERIOD FOR LATE APRIL. FOCAL POINT WILL BE CHECKING WITH PARTNERS...ON WHEN TO START UP THE FROST/FREEZE PROGRAM. MAIN DILEMMA IS THE POPS FOR SATURDAY. TREND TODAY WAS TO INCREASE POPS FOR CENTRAL AND SOUTHERN COUNTIES ON SATURDAY...BUT STILL DIFFICULT TO DETERMINE HOW FAR NORTH TO INCREASE POPS. HAVE INCREASED THE CHANCE POPS INTO THE LIKELY POP RANGE OVER SOUTHERN WV AND SW VA FOR SATURDAY. COLD AIR LINGERS THROUGH MONDAY. COULD NOT RULE OUT SOME FLAKES OVER TALL WV MOUNTAINS...ESPECIALLY BY DAY 7 NIGHT/MONDAY NIGHT. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... COLD FRONT ENTERING THE MOUNTAINS...AND STILL WAITING FOR WIND SHIFTS AT EKN AND BKW. EXPECT THAT TO HAPPEN FAIRLY SOON. ALSO SOME SCATTERED SHOWERS WITH ISOLATED THUNDER ACROSS THE EAST...AND HAVE SOME MVFR AT EKN. FORECAST SOUNDINGS INDICATED POSSIBLE MVFR CIGS TONIGHT BEHIND THE FRONT...ALTHOUGH THINK WE WILL ALSO BE SCATTERING OUT AT THE SAME TIME. TRIED TO REFLECT THIS PROGRESSION IN THE TAFS. VFR EXPECTED TOMORROW WITH GUSTY W TO SW WINDS. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z WEDNESDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: MVFR CIGS MAY LINGER MORE OVERNIGHT IF CLOUDS DO NOT SCATTER OUT AS QUICKLY. 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 TUE 04/21/15 UTC 1HRLY 02 03 04 05 06 07 08 09 10 11 12 13 EDT 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09 CRW CONSISTENCY M M M H H H H H H H H H HTS CONSISTENCY M M H H H H H H H H H H BKW CONSISTENCY H H H H M M H H H M M M EKN CONSISTENCY H H H M M M M M M M M M PKB CONSISTENCY H M H H H H H H H H H H CKB CONSISTENCY M M M H H M H H H H H H AFTER 00Z WEDNESDAY... NO WIDESPREAD IFR CONDITIONS EXPECTED AT THIS TIME. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...KMC/KTB/ARJ NEAR TERM...KMC/MZ SHORT TERM...ARJ LONG TERM...KTB AVIATION...MZ

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