Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 211830 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 230 PM EDT Sat Oct 21 2017 .SYNOPSIS... High pressure continues through Sunday. A strong cold front and low pressure system crosses early next week, with much cooler weather midweek. && .NEAR TERM /THROUGH SUNDAY/... As of 200 PM Saturday... Intervals of cirrus through Sunday as high pressure shifts to the east. Patchy dense river valley fog overnight, but thinking the combination of cirrus and boundary layer winds will keep much of it confined to the mountain valleys. The smoke plume from the large industrial site fire in Parkersburg should back more toward the north overnight and perhaps into the city of Parkersburg. Should more decoupling occur than forecast, poor ventilation rates and lack of dispersion overnight could result in reductions in visibility. Having said that, this is a low confidence scenario, especially considering the uncertainty regarding how much smoldering will exist overnight. Overnight lows were hedged a few degrees below guidance with highs tomorrow on the warm side of the guidance envelope. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... As of 315 AM Saturday... High pressure departing to the NE to start the period as a strong cold front approaches from the west. Slowed down POPs a bit on the front side...keeping the Sunday night period dry. Then have POPs rapidly increasing Monday afternoon with 80-90 POPs late Monday evening and Monday night. Models still struggling a bit with the location of the surface low and cold front, but both GFS and ECMWF pointing to a rainy night. The ECMWF has the front through the forecast area by 12Z Tuesday, while the GFS is a bit slower with the front still crossing the mountains around that time. This appears to be due to the GFS closing off a southern stream upper low over the lower Mississippi River Valley, while the ECMWF keeps it open and more progressive. No strong feeling either way at this point, so stayed close to the consensus blend. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 315 AM Saturday... With the cold front to the east to start the period, attention turns to the trailing upper level trough. The trough axis should be crossing the forecast area early Wednesday, so have lingered chance POPs through most of the day -- envisioning scattered showers as the cold air filters in. GFS continues to be colder than the ECMWF at 850mb -- and have included some snow flakes across the northern mountains both Tuesday night and Wednesday night. Surface temperatures much colder by mid week as well, with highs on Wednesday generally in the 40s and low-mid 50s. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/... As of 210 PM Saturday... General VFR conditions through 06Z amid passing cirrus. 6SM FU was maintained in the KPKB taf through 00Z. The plume has shifted east of the terminal this afternoon, but may shift back over the site this evening for a brief time. Should this occur then brief vsby and/or cig restrictions may be realized given the lowering ventilation rate. Otherwise, boundary layer winds overnight should keep dense fog out of the taf sites, save for late at KEKN. VFR conditions on Sunday with passing cirrus and sw winds to 10 kts. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z SUNDAY... FORECAST CONFIDENCE: High except at PKB. ALTERNATE SCENARIOS: Smoke may restrict vsby and/or cigs for a brief time this evening at PKB. 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 17 18 19 20 21 22 23 00 01 02 03 04 EDT 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00 CRW CONSISTENCY H H H H H H H H H M M M HTS CONSISTENCY H H H H H H H H H M M M BKW CONSISTENCY H H H H H H H H H M M M EKN CONSISTENCY H H H H H H H H H M M M PKB CONSISTENCY H H H H H H H H H M M M CKB CONSISTENCY H H H H H H H H H M M M AFTER 18Z SUNDAY... Dense valley fog possible Sunday morning. Heavy rain at times early next week could also bring IFR conditions. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...RPY/30 NEAR TERM...30 SHORT TERM...MZ LONG TERM...MZ AVIATION...30

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