Area Forecast Discussion
Issued by NWS Charleston, WV

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791 FXUS61 KRLX 211358 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 958 AM EDT Fri Apr 21 2017 .SYNOPSIS... Cold front sags south through this afternoon then lifts back north late Friday night/Saturday. System exits Sunday night/Monday. Dry early next week. && .NEAR TERM /THROUGH TONIGHT/...
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As of 950 AM Friday... Front is moving through the forecast area this morning with most precipitation occurring over northeastern zones. Band should exit CWA shortly. Then short term models hint at weak shortwave entering southern coalfields later this afternoon as it rides along the boundary. This wave, along with some weak diurnal heating should help trigger more shower development today over southern zones. Made some minor adjustments based on latest HiRes short term model data, but overall the idea remains the same. Temp diurnal trend should remain generally flat today and this covered well with inherited forecast. As of 315 AM Friday... Cold front at 07Z gradually entering central Ohio. Progged to enter southeast Ohio by 09Z, Ohio River area around 12Z, and to the east of the higher terrain by 18Z. Several waves moving through the area, will create showers and thunderstorms at times, particularly across southern/eastern zones, where greater moisture will exist. Some partial clearing is expected today, mainly across parts of southeast Ohio, with a mostly cloudy day expected elsewhere. The threat for heavy downpours with any storms will continue today, with a high moisture content atmosphere in place, and pw values around 1.2 inches across the south, generally less than an inch across the north. There is the possibility of a storm across the far south today being on the strong side with wind and hail the primary threat, however, thinking chances are rather low/limited due to overall lack of strong dynamics and expected cloud cover. Overnight, showers and thunderstorms are expected to continue, but there is lots of uncertainty in terms of the timing/location of this as models vary on timing and track of individual waves. For now, kept higher pops across southern zones, with proximity to frontal boundary and higher moisture. The biggest concern during the near term period, is the threat of heavy rain across southern zones. WPC has southern WV and southwest VA highlighted in a marginal threat for excessive rainfall. The nam indicates an axis of heavier precipitation setting up across southern zones later today and tonight, which the other models do not indicate. For now, will allow the day shift to evaluate/monitor the situation and issue any water headlines as necessary.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/... As of 420 AM Friday... This will be a wet period, as low pressure tracks south of the area. It is progged to move from northern Arkansas Saturday morning eastward, across Tennessee Saturday, and then more slowly across the Carolinas Saturday night through Monday night, as it occludes and becomes stacked through the mid and upper levels by Monday morning. Models show 4 to more than six inches rainfall over the central Appalachians through Monday morning, which makes sense given an upper level low tracking slowly south of there. The GFS was the one showing in excessive of six inches, and the outlier there. Otherwise, the models are converging on a solution of three to three and a half inches for roughly the southern third of the forecast area, and at least two inches for the southeast half. The latter is dependent on the exact track of the system and the sharpness / consistency of the northern edge of the heavier rainfall, which comes in several waves. Highlighted the HWO for potentially excessive rainfall through this weekend, and have heavy rain in the grids where PoPs are categorical, roughly the southeast half Saturday and Saturday night. There is a gradual shift southeastward in the rainfall Sunday through Monday, as the system gradually pulls away from the area. Question is how long low level moisture lingers in the southeast half of the area on Monday, and whether low clouds / fog become an issue in the light and variable flow in the wake of the wet system Monday night. Temperatures close to central guidance, except went a little lower Sunday afternoon, which should not be much warmer than Saturday. This wet weekend will also feature highs much lower than recent days and, in fact, break a string of 13 consecutive days with highs in the 70s and 80s at Charleston. && .LONG TERM /TUESDAY THROUGH THURSDAY/... As of 420 AM Friday... Weak high pressure crosses Tuesday. A cold front approaches Wednesday, but then retreats northward, as a warm front Wednesday night, as its driving upper level trough lifts out, and upper level ridging builds. This opens the door to warmer weather, even a summer preview, toward the end of the work week. Central guidance temperatures accepted, climbing well above normal by Friday. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/...
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As of 622 AM Friday... A cold front, with scattered showers and isolated thunderstorms, will gradually sag south into the region through early afternoon, with additional waves, creating more widespread showers and thunderstorms after 15Z, mainly across southwest Virginia and southern West Virginia, with brief MVFR conditions. Behind the front, expecting widespread MVFR conditions to develop, generally 12Z-17Z before some improvement to VFR most locations, although areas of mvfr cigs may still linger, particularly along and south of a line from kckb to kcrw. Additional rounds of showers and thunderstorms, with widespread mvfr and local ifr conditions developing after 09Z. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z SATURDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: More widespread mvfr and ifr conditions may occur than currently 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 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 M H H H M M M M H H H M HTS CONSISTENCY H H H H M M H H H H H M BKW CONSISTENCY H M M M M M M M M M M L EKN CONSISTENCY H M M M L H M H H H H M PKB CONSISTENCY H L M M M H H H H H H M CKB CONSISTENCY H H H H M M H H H H H M AFTER 12Z SATURDAY... IFR possible Saturday into Sunday with another wave of low pressure.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...TRM/SL NEAR TERM...KMC/SL SHORT TERM...TRM LONG TERM...TRM AVIATION...SL is the U.S. government's official web portal to all federal, state and local government web resources and services.