Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 231351 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 951 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/...
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As of 945 AM Sunday... Quick update this morning to several forecast variables. First, bulk of convection moving across the area this morning, associated with upper disturbances moving along a weak boundary, has decreased somewhat. Already starting to see a few breaks in the cloud cover this morning, and this will only help to aid in destabilization once again.Cold frontal boundary still to our north and west, but will gradually sag south towards the region later tonight and on Monday, as a shortwave trough deepens across the area. As it does so, strong unidirectional wind profiles will develop, with 30-40 kts 0-6km bulk shear. With heavy rains previous days, and more on the way, have kept the FFA in place, and also expanded in area to include the entire CWA. Although coal fields and southwest VA counties are drier than other counties, with models indicating areas of heavier convection setting up across these areas today, and WPC guidance, along with the fact that coal fields tend to be rather flash flood prone, in coordination with JKL, decided just to expand the watch area wide through midnight tonight. Area continues to remain in a slight risk for severe today. As of 600 AM Sunday... Convection continues to track east-southeast along the Ohio River into southern WV early this morning. Latest HRRR suggests showers/thunderstorms won`t exit the southern 1/2-1/3 of the area until mid to late morning and have updated POPs to show higher precip probs with longer duration. The other change was to expand Flash Flood Watch to cover more of the southwest portion of the CWA where locally heavy rain continues. The overnight convective rainfall should sufficiently lower 1-3hr FFGs in this area. 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.
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&& .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 /14Z SUNDAY THROUGH THURSDAY/...
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As of 600 AM Sunday... Thunderstorm clusters continue tracking east-southeast along the OH River and gradually weaken across southern WV. Updated 23/09z TAFs to show longer duration of rain over the southern airfields, with pcpn ending 15-17z from west to east based on the latest HRRR. Showers remain isolated over the northeast airspace (in vicinity of KEKN). Also cut back on fog and lower cigs given cloud cover. Additional storms are expected to develop later this afternoon/evening and have indicated VCTS 18-21z. Showers/storms could persist through tonight but confidence is low in the details. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z MONDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Thunderstorm coverage could be more limited later today/tonight. 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 12 13 14 15 16 17 18 19 20 21 22 23 EDT 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19 CRW CONSISTENCY H H L L L H H H H H H M HTS CONSISTENCY H H H H H H H H H H H M BKW CONSISTENCY H M H H H H H H H H H M EKN CONSISTENCY H M M M H M H H H H H M PKB CONSISTENCY H H H H H H H H H H H M CKB CONSISTENCY M M M M M L M H H H H M AFTER 12Z MONDAY... IFR possible Sunday night in heavy showers and thunderstorms. Fog and low ceilings possible early monday morning.
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&& .RLX WATCHES/WARNINGS/ADVISORIES...
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WV...Flash Flood Watch through this evening for WVZ005>011-013>020- 024>034-039-040-515>526. OH...Flash Flood Watch through this evening for OHZ066-067-075-076- 083>087. KY...Flash Flood Watch through this evening for KYZ101>103-105. VA...Flash Flood Watch through this evening for VAZ003-004.
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&& $$ SYNOPSIS...TRM/99 NEAR TERM...SL/99 SHORT TERM...TRM LONG TERM...TRM AVIATION...99

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