Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 191625 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 1225 PM EDT TUE AUG 19 2014 .SYNOPSIS... A VERY WARM...HUMID AND ACTIVE WEATHER PATTERN CONTINUES. AN UPPER LEVEL DISTURBANCE CROSSES TONIGHT. A WARM FRONT SETS UP TO THE WEST OF THE AREA WEDNESDAY NIGHT...AND THEN MOVES INTO THE AREA ON FRIDAY. && .NEAR TERM /THROUGH TONIGHT/... SENT A QUICK UPDATE TO ADJUST POPS PER LATEST RADAR IMAGES SHOWING WEAK CONVECTION ACROSS THE SOUTH AND WESTERN SLOPES OF WV AROUND NOON. EXPECT THIS ACTIVITY TO INCREASE IN COVERAGE AND INTENSITY PER HIGH RESOLUTION MODELS INDICATING INCREASE IN SFC BASED CAPE FROM 1600-2000 J/KG BY THE RAP AND NAM MODELS. THESE VALUES LOOKS REASONABLE COMPARED WITH DEWPOINTS IN THE LOWER 70S ACROSS THE AREA. PWATS IN THE ORDER OF 1.4 INCHES...ACCORDING WITH SATELLITE DERIVED PRODUCTS...AND DIFFERENTIAL HEATING FROM BREAKS IN THE SKY WILL ALLOW CONVECTION TO STRENGTHEN INTO ISOLATED THUNDERSTORMS THIS AFTERNOON AND TONIGHT. MODELS ALSO SHOW A SHORTWAVE AT 5 BRINGING A VORTICITY MAXIMA ACROSS THE AREA BY 06Z WEDNESDAY. THIS FEATURE WILL ENHANCE CONVECTION TONIGHT. INCREASED POPS TO LIKELY WITH THIS LATEST FEATURE. HOURLY TEMPERATURES ADJUSTED AS WELL PER LATEST SFC OBS. PREVIOUS DISCUSSION BELOW... 630 AM UPDATE... FCST ON TRACK. PREV DISCN... ISOLATED SHOWERS WITH PINHEAD DOWNPOURS CONTINUE OVER SE PORTIONS OF THE FCST AREA IN THE WAKE OF AN UPPER LEVEL S/W TROUGH AND SFC LOW THAT CROSSED MON. LOW LEVEL WNW UPSLOPE FLOW AND HIGH PW VALUES ARE LIKELY HELPING TO MAINTAIN THIS ACTIVITY...WHICH SHOULD WANE A BIT FURTHER BUT PERHAPS NOT ALTOGETHER DISAPPEAR LATER THIS MORNING. OTHERWISE LOW CLOUDS WILL BE SLOW TO MIX OUT THIS MORNING...AS THE FOG SLOWLY THINS. THE AREA REMAINS IN A VERY MOIST AND HUMID AIR MASS TODAY WITH INSTABILITY LEADING TO DIURNAL CONVECTION THIS AFTERNOON. THE LACK OF FORCING SUGGESTS THERE WILL NOT BE MUCH COVERAGE...BUT THE LIGHT FLOW THROUGH H5 SPELLS SLOW MOVEMENT ON ANYTHING THAT DOES STAND UP. UPPER LEVEL S/W TROUGH CROSSES TONIGHT...ITS TIMING SLOWER COMPARED WITH PREVIOUS RUNS. ANY SEVERE POTENTIAL WITH IT WILL BE MAINLY W OF THE AREA BECAUSE OF THIS...ALTHOUGH STRONG STORMS CAN MAKE IT INTO THE MIDDLE OHIO VALLEY BEFORE SUNSET. STRATUS AND FOG WILL LIKELY FOLLOW THE SHOWERS AND THUNDERSTORMS LATE TONIGHT. MINOR CHANGES TO TEMPERATURES IN LIGHT OF LATEST BIAS CORRECTED GUIDANCE...A LITTLE WARMER TODAY WITH THE SLOWER SYSTEM...AND ANOTHER VERY WARM AND MUGGY NT TONIGHT. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... UNSETTLED WEATHER IN THE SHORT TERM PERIOD. UPPER LOW/TROUGH MOVING EAST...WITH A MAINLY NWLY FLOW ALOFT...WITH SEVERAL UPPER DISTURBANCES MOVING INTO THE REGION. THIS...COMBINED WITH THE HUMID AIRMASS IN PLACE...WILL KEEP A MENTION OF SHOWERS AND THUNDERSTORMS IN THE FORECAST. PW VALUES DURING THE PERIOD WILL REMAIN RATHER HIGH...GENERALLY 1.5 INCHES OR HIGHER...THUS CONTINUING THE THREAT FOR HEAVY DOWNPOURS. IN ADDITION...COULD BE STORMS ON THE STRONGER SIDE WEDNESDAY/WEDNESDAY NIGHT...PARTICULARLY SOUTHEAST OHIO AND EASTERN KY WHERE BETTER CAPE/SHEAR WILL EXIST. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... USED WPC THINKING WITH SOME TWEAKS. NORTHWEST UPPER LEVEL FLOW IS ANTICIPATED THROUGH MUCH OF THE PERIOD...WITH HIGH PRESSURE TRYING TO BUILD IN LATE. AT THE SURFACE...A NW-SE ORIENTED FRONT SHOULD BE LOCATED NEARBY THROUGH MUCH OF THE PERIOD. WPC TEMPS LOOKED GOOD AND WERE GENERALLY USED. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/... LOW STRATUS DOMINATES EARLY THIS MORNING. IT TOOK THE LOWERING OF IT TO REALIZE DENSE FOG AT HTS AND IT LOOKED LIKE THE SAME THING WAS HAPPENING AT EKN AS 11Z APPROACHED. THE SAME MAY HAPPEN AT OTHER SITES AS WE NEAR AND CROSS THE START OF THE 1912/2012 TAF PERIOD. THE FOG WILL THIN INTO AN MVFR MIST BY MID MORNING BEFORE DISAPPEARING ALTOGETHER...BUT IT WILL TAKE MUCH OF NOT ALL OF THE MORNING FOR THE STRATUS TO LIFT THROUGH AND THEN ABOVE THE MVFR RANGE. MVFR STRATOCU MAY HANG ON INTO THE AFTERNOON IN THE MOUNTAINS. THE PROBLEM TONIGHT WILL BE THUNDERSTORMS...ALTHOUGH THIS FCST IS ALSO A BIT UNCERTAIN. THE STORMS SHOULD FIRE UP IN THE MIDDLE OHIO VALLY AS A SYSTEM APPROACHES FROM THE NW LATER TODAY. THE STORMS WILL MOVE QUICKLY SEWD THROUGH THE MIDDLE OHIO VALLEY AND THEN THE CENTRAL APPALACHIANS TONIGHT. POST RAIN STRATUS AND FOG ARE LIKELY TO FORM IN THE WAKE OF THE SHOWERS AND THUNDERSTORMS BY DAWN WED. LIGHT AND VARIABLE SFC FLOW WILL BECOME LIGHT SW TONIGHT...WHILE LIGHT NW FLOW ALOFT BECOMES LIGHT W THIS AFTERNOON AND THEN LIGHT SW TONIGHT. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z WEDNESDAY... FORECAST CONFIDENCE: LOW TO MEDIUM. ALTERNATE SCENARIOS: TIMING OF LIFTING AND DISSIPATION OF LOW STRATOCU...STRATUS AND FOG THIS MORNING MAY VARY. TIMING OF AND CONDITIONS IN THUNDERSTORMS LATE TODAY AND TONIGHT MAY VARY. IFR IS POSSIBLE RIGHT BENEATH ANY THUNDERSTORM LATE TODAY AND TONIGHT. THE THUNDERSTORMS MAY ALSO PRODUCE STRONG WIND GUSTS IN THE MIDDLE OHIO VALLEY THIS EVENING. TIMING AND EXTENT OF FOG AND STRATUS LATE OVERNIGHT TONIGHT MAY ALSO VARY FROM FCST. 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 14 15 16 17 18 19 20 21 22 23 00 01 EDT 1HRLY 10 11 12 13 14 15 16 17 18 19 20 21 CRW CONSISTENCY L H M M M H H H H H H H HTS CONSISTENCY M H H H H H H H H H H H BKW CONSISTENCY H H H H H H M 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 M M M H H H H H H H H AFTER 18Z WEDNESDAY... IFR POSSIBLE IN ANY ROUND OF CONVECTION WED NT THROUGH FRI NT...AND IN LATE NT/EARLY MORNING POST RAIN FOG AND STRATUS THROUGH SAT MORNING. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...TRM/SL NEAR TERM...ARJ/TRM SHORT TERM...SL LONG TERM...JSH AVIATION...TRM

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