Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 271843 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 243 PM EDT TUE SEP 27 2016 .SYNOPSIS... A large upper level low drops into the area Wednesday and Wednesday night, and then swirls about the area Thursday through Saturday, before pulling away Sunday. && .NEAR TERM /THROUGH WEDNESDAY/... As of 1121 AM Tuesday... A broad and strong upper to mid level low pressure system will move south over the OH Valley and WV tonight into Wednesday night and Thursday. This low will bring some forcing, but with dry atmosphere, showers or storms will stay in the light side. The low will rotate overhead through the end of the week. A new air mass is in place with dewpoints in the mid 40s, slowly increasing into the 50s late Wednesday. Patchy river valley fog will likely develop over the preferred sites, EKN and CRW overnight. Used the super blend and all blend for temperature through the period. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... As of 430 AM Tuesday... The weather this period will be governed by a large upper level low, which begins the period, 12Z Wednesday, near Chicago, and ends the period, 12Z Saturday, in nearly the same area, maybe closer to Toledo or Indianapolis. The system is progged to dig southeastward into eastern Kentucky Wednesday and Wednesday night, and then rotate through the forecast area Thursday and Thursday night, before retreating northwestward, back through Ohio, Friday and Friday night. The closed low cuts off from the main westerlies as it digs southeastward early in the period and prior, and then basically meanders beneath a rex block thereafter. After depicting more progressive solutions, models have increasingly converged on this solution over the past several runs. The system drives a cold front through the area Wednesday into Wednesday night, as it digs southeastward toward the area, and then surface low pressure whirls about the area thereafter. After a dry start, a line of showers and thunderstorms is likely to cross the middle Ohio Valley ahead of the approaching cold front on Wednesday, before lifting northward late Wednesday beneath the upper level south to southwest flow. Some of the showers should be able to push into the central Appalachians late Wednesday into Wednesday night. Additional embedded upper level short wave troughs rotating around the upper level low late Wednesday night through Friday night will be increasingly tough to time with increasing forecast projection, but diurnal heating below the low upper level heights and temperatures will result in greater coverage of showers during the afternoon and early evening hours, when thunderstorms will also be possible. Not coded, small hail may not be out of the question given freezing levels dropping to 7-8 kft. For now, it appears the system, whirling about the Ohio Valley, will be far enough east so that an anomalous inflow of moisture ahead of it will set up east of the forecast area, and so will the more persistent, heavy, and potentially excessive, rainfall. Lowered highs into the middle Ohio valley Wednesday given the timing of the cold front, and associated showers and thunderstorms. Once the cold front is through, temperatures will be below normal, especially on highs, with small temperature ranges given lots of cloudiness spiraling about the upper level low. Only minor changes were needed in light of the latest guidance, leaning toward bias corrected guidance at night. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 320 PM Monday... Operational and ensemble guidance is in pretty good agreement with large upper level low remaining overhead well into the weekend. With the cool temperatures aloft...any daytime heating we receive will quickly yield showers and possible isolated thunderstorms. The good news is that this should bring some much needed rainfall to the region and amounts will remain light enough so we are not expecting any hydro issues. The upper low meanders northward Sunday into Monday with ridging moving in behind it. This will bring warm air back into the region with upper 70s to near 80 degrees for the start of the next work week. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... As of 130 PM Tuesday... Satellite and radar image show clear skies across the entire area. A deep low pressure system over the Great Lakes region, will move south over the OH Valley and WV tonight. Expect mostly clear skies tonight. With radiational cooling, IFR/LIFR river valley fog will develop most likely at EKN, CRW, and HTS. Any dense fog should dissipate by 13-14Z. Widespread VFR conditions expected Wednesday. However, vorticity maxes around the low`s center could bring some forcing and chances for showers or storms Wednesday night into Thursday. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z WEDNESDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Development and extent of any fog overnight may vary from 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. 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 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 H H H H H H H M M L PKB CONSISTENCY H H H H H H H H H H H M CKB CONSISTENCY H H H H H H H H H H H M AFTER 18Z WEDNESDAY... Morning valley fog possible through Friday morning. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...ARJ/SL NEAR TERM...ARJ SHORT TERM...TRM LONG TERM...MPK AVIATION...ARJ is the U.S. government's official web portal to all federal, state and local government web resources and services.