Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 230821 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 421 AM EDT Sun Jul 23 2017 .SYNOPSIS... Strong to severe thunderstorms are still possible today, with a risk for heavy downpours as well. A cold front crosses tonight, and then another crosses Monday night. High pressure midweek. && .NEAR TERM /THROUGH TONIGHT/... As of 230 AM Sunday... Thunderstorm clusters tracking east-southeast along the OH River into southwest WV/northeast KY have been exhibiting a general weakening trend. Updated POPS based on the latest HRRR which indicates the southern 1/2 to 1/3 of the CWA will see rain through the predawn and into the early morning hours. Well-defined shortwave over northern MN early this morning will move east through the Great Lakes with general synoptic trough amplification into the central Appalachians by the end of the period. Several vorticity maxima will rotate through the southern edge of the trough and ahead of a cold front pressing southeast through the OH Valley. The combination of increasing large scale forcing/ascent associated with vort maxes, residual outflow boundaries, rich moisture (70+ dewpoints) and moderate instability should all prove effective in generating more storms this afternoon into tonight. Much like yesterday, storms will be capable of isolated damaging winds and localized heavy rainfall. 1-3hr FFG is quite low (an inch or less) across the northern 1/2 of the CWA and may need to extend FFA beyond 12z expiration. Lastly, max HX values approach 100F around the Tri-State area and will need to monitor convective/cloud trends for possible advisory. && .SHORT TERM /MONDAY THROUGH WEDNESDAY NIGHT/... As of 420 AM Sunday... Monday begins with low cloud given lots of low level moisture in place in the wake of rounds of convection over the weekend. With the morning cu effect, it may take much of the morning for these clouds to mix higher and then mix out. This will then modulate the amount of instability we could realize Monday afternoon, to take advantage of marginal deep layer bulk shear, ahead of a cold front approaching from the northwest. With drier mid level air limiting high PW values to smaller pockets, coverage of storms should be limited, and so should the excessive rainfall threat. The front will cross Monday night, with dry weather overnight through Tuesday night, and into Wednesday morning, as high pressure crosses. That high exits on Wednesday, allowing a return flow of warmer and more humid air from the south. This may be sufficient for elevated heat source effect convection in the mountains Wednesday afternoon and evening. That diurnal convection will wane Wednesday night. Temperatures only get a scosh below normal in the relatively refreshing canadian air, in which central guidance was below the MEX for lows in the Tygart Valley Tuesday. && .LONG TERM /THURSDAY THROUGH SATURDAY/... As of 420 AM Sunday... Models agree on a new cold front approaching from the northwest late Thursday and Thursday night, and then crossing the area Friday. The chance for showers and thunderstorms increases in the warmer and more humid air ahead of the front Thursday afternoon, with the help of diurnal heating. Showers and thunderstorms are likely Thursday night into Friday, as the front approaches. The passage of the front will bring drier weather into the middle Ohio Valley Friday afternoon, and then the central Appalachians Friday night. High pressure will build in behind the front, for a dry, cooler and less humid weekend. Temperatures reflect a return to the very warm weather on Thursday, followed by a cooling trend, largely on account of the clouds and rain associated with the front on Friday, and then below normal in the wake of the front over the weekend. Central guidance is again below the MEX for lows in the Tygart Valley over the weekend. && .AVIATION /07Z SUNDAY THROUGH THURSDAY/... As of 230 AM Sunday... Upstream thunderstorm clusters tracking east-southeast along the OH River will bring rain to the southern 1/2 to 1/3 of the airspace during the predawn hours and into the early morning. Can`t rule out a few showers/storms into the northern airspace but these would be more isolated in coverage. Restrictions in the northern airspace should be related to fog/low cigs with thunderstorm with rain brief mod-hvy rain at KHTS/KCRW. High res guidance shows a break in convection 12-15z. Additional storms are expected to develop across the airspace during the afternoon and evening and have indicated VCTS after 17z. Storm could persist into tonight but confidence is low on the evolution. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z MONDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Convection could be less widespread than currently forecast. Conditions on Sunday may not improve as quickly as currently forecast. 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 SUN 07/23/17 UTC 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 EDT 1HRLY 02 03 04 05 06 07 08 09 10 11 12 13 CRW CONSISTENCY H H H H H H M H H H H M 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 M EKN CONSISTENCY H H M L M M M M M L M L PKB CONSISTENCY M M M M M M M M M H L L CKB CONSISTENCY M M M M M M L H M L L L AFTER 06Z MONDAY... IFR possible Sunday night in heavy showers and thunderstorms. Fog and low ceilings possible early monday morning. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...Flash Flood Watch until 8 AM EDT this morning for WVZ007>011- 014>020-027>032-039-040-517>526. OH...Flash Flood Watch until 8 AM EDT this morning for OHZ066-067- 075-076-083>086. KY...None. VA...None. && $$ SYNOPSIS...TRM/99 NEAR TERM...99 SHORT TERM...TRM LONG TERM...TRM AVIATION...99 is the U.S. government's official web portal to all federal, state and local government web resources and services.