Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 202342 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 742 PM EDT SUN APR 20 2014 .SYNOPSIS... DRY ATMOSPHERE WITH COOL NIGHTS AND WARM DAYS HOLDS ON THROUGH MONDAY. COLD FRONT WITH MORE AVAILABLE MOISTURE CROSSES TUESDAY. HIGH PRESSURE MIDWEEK. ANOTHER COLD FRONT CROSSES FRIDAY. && .NEAR TERM /THROUGH MONDAY/...
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730 PM UPDATE... NO CHANGES TO ONGOING FORECAST. RH VALUES STILL DOWN IN THE 11-15 PERCENT RANGE AT THE TOP OF THE HOUR HOWEVER. MAY KEEP THE ENHANCED FIRE DANGER SPS GOING AN ADDITIONAL COUPLE OF HOURS THIS EVENING WITH EXCEPTIONALLY DRY AIR AND DRY CONDITIONS IN PLACE. PREVIOUS DISCUSSION... NO MAJOR CHANGES WERE NEEDED IN THE NEAR TERM PERIOD FROM PREVIOUS FORECAST. DRY ATMOSPHERE IN PLACE...PARTICULARLY IN LOWER LEVELS...AND DAYTIME HEATING/MIXING...HAS RESULTED IN RATHER LOW RELATIVE HUMIDITIES THIS AFTERNOON...AS EXPECTED. RELATIVE HUMIDITIES ACROSS MUCH OF THE AREA HAVE ALREADY DIPPED INTO THE TEENS AS OF 17Z. FORTUNATELY...WINDS REMAIN RATHER LIGHT THUS MITIGATING A MAJOR FIRE ISSUE...BUT HAVE A SPS IN EFFECT UNTIL 00Z TO ACCOUNT FOR THE DRY FUELS/ATMOSPHERE. WITH THE VERY DRY ATMOSPHERE IN PLACE...EXPECTING PERIOD OF COOL NIGHTS...AND WARM SUNNY DAYS TO CONTINUE IN THE NEAR TERM PERIOD. CLOUDS AND DEW POINTS WILL GRADUALLY INCREASE TOMORROW OUT AHEAD OF NEXT APPROACHING SYSTEM...TO AFFECT AREA MONDAY NIGHT AND TUESDAY. DID ELECT TO ADD A SLIGHT CHANCE FOR SHOWERS ACROSS FAR WESTERN ZONES...MAINLY EASTERN KY...MONDAY EVENING. ELECTED TO LEAVE THUNDER OUT OF FORECAST FOR NOW DUE TO TIMING OF POPS. LAST CHECK OF RAWS OBSERVATIONS IN SOUTHWEST VA SHOW FUEL MOISTURE SLIGHTLY HIGHER THAN REST OF CWA...SO FOR NOW...WILL CONTINUE TO KEEP THEM OUT OF THE SPS.
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&& .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... ALL MODELS SAVE FOR THE CANADIAN ARE FASTER WITH A COLD FRONT NOW CROSSING TUE MIDDAY AND AFTERNOON. LEAD SRN STREAM UPPER LEVEL S/W TROUGH OUT AHEAD OF MAIN SYSTEM CROSSES OVERNIGHT MON NT...GRADUALLY MOISTENING UP WHAT IS INITIALLY A DRY...RELATIVELY DEEP MIXED LAYER...LEADING TO AN INCREASING CHANCE FOR SHOWERS FROM W TO E OVERNIGHT MON NT. AIR MASS JUST TO THE W OF THE CWA BECOMES SLIGHTLY UNSTABLE IN THE HEATING OF TE DAY...GIVING RISE TO THE CHANCE FOR THUNDERSTORMS UPSTREAM...WHICH COULD THEN SURVIVE THEIR EWD TREK INTO THE CWA TUE NT. GENERALLY HAVE LIKELY POPS AHEAD OF THE COLD FRONT AS IT APPROACHES TUE MORNING BEFORE CROSSING MIDDAY INTO THE AFTERNOON...WITH THE BEST CHANCE FOR THUNDER DURING THAT TIME ALTHOUGH A BRIEF UP TICK IS POSSIBLE IN THE AFTERNOON HEATING IN THE ERN HALF OF THE CWA. PW VALUES DO INCREASE TO 1.25 INCHES BUT THE SYSTEM WILL BE PROGRESSIVE. CAPE VALUES INCREASE TO 600 J KG-1 OFF NAM12 WITH ITS HIGH DEW POINTS...GFS PEAK CAPE IS MUCH LESS. WITH H8 WINDS TO 40 KTS...GUSTY WINDS AND BRIEF HARD DOWNPOURS ARE POSSIBLE. PRECIPITATION MOVES OUT QUICKLY TUE EVENING...FOLLOWED BY SOME CLEARING FROM THE W. LOW CLOUD EPISODE WILL BE BRIEF BEHIND THIS POLAR / PACIFIC FRONT...WITH MORNING CU LIKELY TO BE LIMITED TO THE MOUNTAINS AND SRN WV COAL FIELDS. OTHERWISE WEDNESDAY WILL BE DRY WITH PLENTY OF AFTERNOON SUN...AS HIGH PRESSURE BUILDS INTO THE AREA FROM THE NW. TEMPERATURES FROM PREVIOUS PACKAGE LOOKED GOOD...BLENDED IN A LITTLE OF THE BIAS CORRECTED MET ON LOWS...HIGHER THAN THE MAV NUMBERS...AND A LITTLE OF THE STRAIGHT MET FOR HIGHS TUE...AND A LITTLE OF THE STRAIGHT MEX FOR HIGHS WED. HIGHS TUE ARE JUST AS LIKELY TO OCCUR IN BREAKS IN THE CLOUDS BEHIND THE FRONT LATE AS EARLIER IN THE DAY AHEAD OF THE FRONT...ESPECIALLY W. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... HIGH PRESSURE BEHIND MID WEEK COLD FRONT BRINGS DRIER AND PLEASANT TEMPERATURES FOR WEDNESDAY AND WEDNESDAY NIGHT...WITH A QUICK WARM UP THURSDAY AND FRIDAY AHEAD OF AN APPROACHING NEW COLD FRONT. MODELS...ECMWF/GFS HAVE MAINTAIN CONSISTENCY DURING THE PAST FEW DAYS...SLOWING DOWN THE COLD FRONT EARLY FRIDAY MORNING...WITH PCPN CONTINUING THROUGH FRIDAY AS IT EXITS NORTHEAST. THIS TIMING IS NOT DURING THE PEAK DIURNAL HEATING UNDER CUTTING THUNDERSTORM PROBABILITY. MODELS DO SHOW HIGH DEEP LAYERED SHEAR AS WITH MOST COLD FRONTS. BUT TOO FAR OUT TO TRUST THERMODYNAMIC PARAMETERS. KEPT INCREASE IN DEWPOINT AHEAD AND ALONG THE COLD FRONT. USED HPC GUIDANCE FOR TEMPERATURES AS NOTICED ONLY MINOR CHANGES FROM PREVIOUS DAYS. KEPT POPS TO 51 PERCENT TO ACCOUNT FOR QPF ON GRIDS. POPS COULD BE INCREASE TO LIKELY OR CATEGORICAL WITH FRIDAYS COLD FRONT AS TIME APPROACHES. SHOWER ACTIVITY LINGERS FRIDAY NIGHT FOR SLIGHT CHANCE POPS. HIGH PRESSURE BUILDS BEHIND THE FRONT FOR THE WEEKEND PROVIDING FRESH AIR FROM THE NORTH. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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00Z MONDAY THROUGH 00Z TUESDAY... VFR CONDITIONS WITH LIGHT SURFACE WINDS WILL PREVAIL THROUGH THE PERIOD. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z TUESDAY... FORECAST CONFIDENCE: HIGH. ALTERNATE SCENARIOS: NONE. 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 MON 04/21/14 UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11 EDT 1HRLY 20 21 22 23 00 01 02 03 04 05 06 07 CRW CONSISTENCY H H H H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY H H H H H H H H H H H H EKN CONSISTENCY H H H H H H H H H H H H PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H H H H H H H H H H H H AFTER 00Z TUESDAY... NO IFR CONDITIONS EXPECTED.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...ARJ/TRM/SL NEAR TERM...50/SL SHORT TERM...TRM LONG TERM...ARJ AVIATION...50

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