Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 232022 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 322 PM EST Thu Feb 23 2017 .SYNOPSIS... Unseasonably warm through Friday. A strong cold front crosses pre- dawn Saturday morning, followed by cooler weather for the weekend. A couple systems next week with precipitation chances. && .NEAR TERM /THROUGH FRIDAY/... As of 120 PM Thursday... Widely scattered showers associated with warm advection and weak upper level short wave trough should be gone by late afternoon, as the upper level wave exits. Otherwise a warm southwest flow of unseasonably warm air dominates this period. Forcing associated with a cold front approaching from the west late Friday, and the associated convective threat, is progged to hold west of the forecast area through 23Z Friday. Inherited temperatures were accepted, close to guidance tonight and a little above on Friday, not to mention as much as 8 degrees above record highs for Friday. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
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As of 310 PM Thursday... Possible severe weather late Fri night into Sat morning... Strong cold front approaches the region late Friday night. Out ahead of the front a line of showers and thunderstorms will be likely, but there is still a bit of uncertainty on how strong this line of convection will be as it enters the Ohio Valley. Although an EML plume pushes over the area, with Mid-level lapse rates maxing out at 8.5C/km by 00Z Saturday, a strong cap will be in place. By the time the front pushes in several hours later, the plume shifts east, but lapse rates remain in the 7 to 7.5C/km range with colder air aloft moving in with the upper trough. Low level moisture is quite limited and CAPE values overnight only are in the 300 to 600 J/kg range. This will certainly be a limiting factor, however the concern for severe weather still remains because of the very strong 0-6km bulk shear of +50 knots out ahead of the front. The strong lapse rates and marginal instability should still be enough to keep an upstream QLCS intact as it crosses our region, however it is likely to weaken considerably as it pushes east. It will be likely that any line of convection will have strong wind gusts with it, and given the strong unidirectional shear it is possible that some damaging winds will be possible. The greatest threat will be in the Ohio Valley and a decreasing threat is expected as the system head east. The front will exit the region later Saturday morning and colder air pushes in behind it. There is potential that with the cold air advection and NW flow behind the front that we see a few upslope snow showers across the mountains. However, moisture is very limited so very little accumulation is expected. High pressure will build in Sunday and snow showers come to an end Sunday morning.
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&& .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 320 PM Thursday... High pressure will be drifts eastward Sunday night. A southern stream driven system pushes into the area on Monday. GFS us still more robust and a bit earlier with this system than the ECMWF. Due to the uncertainty, I went with a blend of ensemble and operational guidance for this period which gives low chance PoP for now. The next system moves in midweek as a surface low comes out of the Rockies. Current guidance has this system passing to our north and dragging a cold through the region Wednesday night. With decent agreement between the overall guidance, have decided to go with likely PoP even being Day 6 of the forecast. && .AVIATION /21Z THURSDAY THROUGH TUESDAY/... As of 120 PM Thursday... Morning MVFR cu was most persistent over the western lowlands early this afternoon. It may take until 20-21Z for it to mix out over the middle Ohio Valley. MVFR mist is possible in the deeper valleys overnight tonight, Otherwise VFR conditions prevail in a south to southwest flow of unseasonably warm air. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z FRIDAY... FORECAST CONFIDENCE: Medium to High. ALTERNATE SCENARIOS: MVFR stratocu may persist more than forecast this afternoon. MVFR (or worse) valley fog may affect more sites than EKN overnight tonight. Increasing flow will lessen the chance toward dawn Friday. 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 EST 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00 CRW CONSISTENCY H H H H H H H H H H H M HTS CONSISTENCY M 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 H H H H H H H H H M PKB CONSISTENCY M M H L H L H H H H H M CKB CONSISTENCY H M H M H H H H H H H M AFTER 18Z FRIDAY... No widespread IFR conditions are expected at this time. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...TRM/MPK NEAR TERM...TRM SHORT TERM...MPK LONG TERM...MPK AVIATION...TRM

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