Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 031747 AFDRLX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE CHARLESTON WV 147 PM EDT THU SEP 3 2015 .SYNOPSIS... WEAK HIGH PRESSURE AND WEAK STEERING FLOW CONTINUES. SOUTHEAST FLOW DEVELOPS FRIDAY NIGHT INTO SATURDAY. INSTABILITY DRIVEN BY DIURNAL HEATING PRODUCES ISOLATED TO SCATTERED CONVECTION. && .NEAR TERM /THROUGH TONIGHT/... UPDATE... LOTS OF INSTABILITY ABOVE THE BOUNDARY LAYER DESPITE MEAGER MOISTURE AVAILABILITY...SO IT IS NOT TAKING MUCH TO FIRE SHOWERS AND STORMS THIS MORNING. A COUPLE OF WEAK VORT MAXES ARE CURRENTLY DOING THE TRICK. HAVE ADJUSTED THE GRIDS ACCORDINGLY. THERE MIGHT BE A LAG AROUND 16Z IN THE COVERAGE WITH IT RAMPING UP AGAIN HEADING INTO THE AFTERNOON...BUT WILL JUST SLOWLY INCREASE THE COVERAGE OF THE SLIGHT/CHANCE THROUGH THE PERIOD. PREVIOUS DISCUSSION... AREAS OF RIVER VALLEY FOG WILL QUICKLY DISSIPATE BY 12-13Z. SATELLITE AND RADAR IMAGES SHOW CLOUDS AND ISOLATED LIGHT SHOWERS AND STORMS MOVING SOUTH INTO NORTHERN WV EARLY THIS MORNING. THIS ACTIVITY SHOULD DISSIPATE AS INSTABILITY IS LIMITED. BETTER CHANCES FOR ADDITIONAL SHOWERS AND STORMS ARE EXPECTED ONCE AGAIN TO DEVELOP THIS AFTERNOON. WITH DEWPOINTS IN THE MID 60...SFC BASED CAPE EXCEEDING 2500 J/KG...AND EQUILIBRIUM LEVELS REACHING 40 THOUSAND FEET THIS AFTERNOON...EXPECT TALLER STORMS CAPABLE TO PRODUCE STRONG GUSTY WINDS. RAINFALL SHOULD BE MODERATE TO HEAVY IN SOME SPOTS. PATCHY DENSE FOG COULD DEVELOP ALONG RIVER VALLEYS ONCE AGAIN OVERNIGHT TONIGHT. FOG FORMATION WILL DEPEND ON CLOUD COVER AND AREAS THAT RECEIVE RAIN. TEMPERATURES WILL RISE INTO THE UPPER 80S LOWLANDS THIS AFTERNOON...AND THEN DROP INTO THE MID TO LOWER 60S TONIGHT. MINOR CHANGES MADE TO PREVIOUS FORECAST AS THEY WERE SIMILAR TO THE ALL BLEND GUIDANCE. && .SHORT TERM /FRIDAY THROUGH SUNDAY NIGHT/... BROAD AREA OF LOW PRESSURE IS CAUSING WEAK FLOW GIVING WIDELY SCATTERED AFTERNOON SHOWERS AND THUNDERSTORMS FOR FRIDAY AND SATURDAY. THESE WOULD BE SLOW MOVERS...WITH A LOCAL DOWNPOUR. OVERALL THOUGH...THE AREA REMAINS IN A RELATIVELY DRY PATTERN THROUGH LABOR DAY AND SHOWERS MAY EVEN BE HARD PRESSED TO FORM ON LABOR DAY AS A WEAK LOBE OF HIGH PRESSURE NUDGES IN. WEAK VORT MAXES CONTINUE TO LINGER IN THE REGION...BUT THEIR WHEREABOUTS ARE ERRATIC AND DIFFICULT TO PREDICT. && .LONG TERM /MONDAY THROUGH THURSDAY/... 12Z GFS SOLUTION WAS FASTER THAN THE 12Z ECMWF WITH A SHORT WAVE AND ASSOCIATED SURFACE FRONT TRYING TO DENT THE RIDGE BY DAY 7/TUESDAY. AT THIS DISTANCE IN TIME...WILL NOT JUMP ON THE FASTER SOLUTION BUT STILL HAVE CHANCE POPS IN SE OHIO AND NORTHERN WV TUESDAY AFTERNOON AND EVENING. TRIED TO HOLD MAXIMUM TEMPERATURE DOWN A BIT FOR DAY 4/SATURDAY IN THE SOUTHEAST UPSLOPE AREAS...OTHERWISE NO MAJOR CHANGES. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/... ISOLATED TO SCATTERED CONVECTION NOW FIRING ACROSS THE AREA WARRANTING VCTS FOR THE 19Z TO 23Z PERIOD. NO PREVAILING TSRA IN THE TAFS FOR NOW...WHICH SHOULD IN THEORY LEAD TO A FOG FORECAST SIMILAR TO CONDITIONS LAST NIGHT. HOWEVER...CLOUD COVER REMAINS A CHALLENGE IN THIS ENVIRONMENT...AND IF TERMINALS RECEIVE RAIN AFTER A PROLONGED DRY PERIOD...FOG TIMING COULD CHANGE AND INCREASE. MORE CONVECTION EXPECTED FRIDAY...ISOLATED TO SCATTERED...IN THIS PERSISTENT PATTERN. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z FRIDAY... FORECAST CONFIDENCE: MEDIUM. ALTERNATE SCENARIOS: TIMING AND COVERAGE OF FOG TONIGHT MAY VARY FROM FORECAST. MAY NEED AMENDMENTS AND TEMPOS IF STORMS FORM/MOVE TOWARDS TERMINALS. 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 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 M 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 M H M PKB CONSISTENCY H H H H H H H H H M M M CKB CONSISTENCY H H H H H H H H H H M M AFTER 18Z FRIDAY... IFR POSSIBLE IN VALLEY FOG FRIDAY NIGHT. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...NONE. OH...NONE. KY...NONE. VA...NONE. && $$ SYNOPSIS...JSH/JMV NEAR TERM...ARJ/26 SHORT TERM...JW LONG TERM...FB/KTB AVIATION...26

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