Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 261845 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 245 PM EDT Fri May 26 2017 .SYNOPSIS... Weakening MCS tonight. Storms Saturday with a frontal boundary and high instability. && .NEAR TERM /THROUGH SATURDAY/... As of 225 PM Friday... Synoptically, flow aloft will turn zonal tonight, while a warm front pushes northward. Awaiting a cold front dropping back southward through the CWA Saturday as a result of a surface wave passage. High res and synoptic models remain keen on the development of a MCS in northern Illinois/Indiana later this afternoon and evening, tracking into middle/upper Ohio Valley. Biggest question here is the exact track with the high res models taking the southern extent closer to the I-64 corridor, despite steering flow suggesting that it should stay a bit further north. Concentrating those POPs tonight along US 50, but this complex will likely be on the wane as it enters the CWA, or shortly after. Atmosphere should have plenty of time to recover after dawn in the warm sector. CAPE values are in line with the frontal position as expected, and with the cold front sinking southward through the afternoon, this should be a southern two thirds of the CWA severe/water event. Will need to carry slight to low chance however north of the boundary. Decent 0-6km flow around 40kts and instability warranting the slight risk for the area south of the front, with the enhanced area closer to our area from the latest SPC issuance. Water cannot be ignored either. Very saturated in terms of surface conditions and creek/stream levels, and any sort of repetitive activity will cause problems. Flash flood guidance values are quite low given the recent wet trend. Convective activity Saturday will largely dictate the weather heading into Saturday night and Sunday. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... As of 5 AM Friday... A roughly west-northwest to east-southeast oriented front, roughly parallel to the upper level flow, will oscillate about the area Saturday into Sunday, modulated on the mesoscale by thunderstorm complexes that are likely to form along or near it. This begins with a modest 25 kts h85 LLJ Saturday morning along a theta e axis in which h85 dew points climb from 12 to 15C. Deep layer bulk shear as high as 50 kts Saturday morning decreases to 40 kts south and only 20 kts north Saturday afternoon, while CAPE increase to near 3 kj/kg south and central portions of the area Saturday afternoon, so southern to perhaps central portions of the area appear favored for the strongest thunderstorm development Saturday afternoon and evening. Depending upon how the convection evolves Saturday into Saturday night, cool pooling could effectively push the boundary south Saturday night, setting up another warm advection feed Sunday morning. The h85 is progged to peak near 35 kts overnight Saturday night, before decreasing again, but bulk shear is forecast to increase to over 50 kts again overnight Saturday night and continue through Sunday, while CAPE forecast values vary among models but are forecast to be highest west. Upper level ridging crosses Saturday night, switching the upper level flow from west-northwest Saturday to west-southwest on Sunday, with embedded short wave troughs tied to convective mesoscale complexes, but with a general tendency to push the front northeastward into Sunday night. Will maintain heavy rain and strong thunderstorm wording in HWO and state briefing, but, in collaboration with neighboring offices, will wait until we get a little closer to convective development to begin timing and placement of any needed flash flood watches. A cold front crosses overnight Sunday night, leading to a drier weather pattern to start the new work week. The mesoscale dominated pattern is likely to result in variation from central guidance temperatures with time, which show small diurnal ranges not far from normal on average. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 5 AM Friday... A weak cold front crosses Tuesday beneath upper level northwest flow, with surface high pressure and upper level ridging remaining well out to the west. The high does pass south of the area on Wednesday, and another upper level short wave trough is progged to drive a new surface cold front into the area Wednesday night and Thursday. It may taken the better part of Friday to push that front through the area. Central guidance temperatures accepted, largely near normal. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... As of 125 PM Friday... VFR through the afternoon with wind gusts 20-25kts and cumulus above 4kft. Complex of storms moves in from the west northwest after 05Z Saturday, and will likely be on the slow wane. However, TSRA and IFR visibilities are likely at PKB and CKB, but carry only SHRA into EKN by the time it reaches that terminal. The southern sites of HTS, CRW, and BKW will likely be on the fringe of this activity, so some restrictions may have to be added here with a track that goes a bit further to the south. All models are holding strong on decreasing ceiling heights into the late morning hours, so carry MVFR during this time. Cold front drops south, so the bulk of the afternoon convection should be relegated south of PKB-CKB-EKN. That said, leaving low chances for convection across the north. Forecast Confidence: High through 06Z. Medium after. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS FORECAST CONFIDENCE: FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z SATURDAY... across northern terminals.. EXPERIMENTAL TABLE OF FLIGHT CATEGORY NOT AVAILABLE 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 L L L L L L L L L L L L HTS CONSISTENCY L L L L L L L L L L L L BKW CONSISTENCY L L L L L L L L L L L L EKN CONSISTENCY L L L L L L L L L L L L PKB CONSISTENCY L L L L L L L L L L L L CKB CONSISTENCY L L L L L L L L L L L L AFTER 18Z SATURDAY... IFR likely in showers and storms Saturday night and Sunday. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...TRM/SL NEAR TERM...26 SHORT TERM...TRM LONG TERM...TRM AVIATION...26

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