Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 210838 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 438 AM EDT Fri Jul 21 2017 .SYNOPSIS...
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Thunderstorm activity on the increase, with strong to severe storms possible this weekend. Frontal system passes early next week. Cooler high pressure crosses midweek.
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&& .NEAR TERM /THROUGH TONIGHT/...
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As of 400 AM Friday... A consensus of the latest high res model guidance continues to indicate max precip potential across the northern portions of the area this morning. An isolated/brief heavy downpour is psbl. Both high res and larger scale model guidance remain fairly bullish on scattered thunderstorm development during the afternoon. SPC has shifted the MRGL severe storm risk to the northwest, with lack of deep-layer shear likely the limiting factor. Locally heavy rain is a concern with moderate instability and PW values 1.5-2.0+ inches. Some convection may linger into early tonight but overall expect a gradual decrease in coverage/intensity. Hot/humid conditions are expected again this afternoon with max heat index values in the upper 90s to low 100s from the southern WV lowlands into northeast KY/srn OH. No changes to the heat advisory.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY NIGHT/...
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As of 430 AM Friday... Saturday begins with a warm front over northeastern WV, which pushes to the north and east of the area in the morning. This paves the way for southwest flow to keep the high heat and humidity going throughout the area Saturday. PoP grids reflect diurnal convection beginning by midday given the high dew points, perhaps slower timing of the warm front, and/or outflow boundaries from previous convection. An upper level short wave trough and low pressure system passing north of the area drive a cold front southward through the area Saturday night through Sunday night. This gives rise to the increasing chance for thunderstorms, especially during the afternoon and evening hours, as the strengthening flow associated with the system provide sufficient deep shear to take advantage of CAPE values up to 3 kj/kg Saturday and even 4 kj/kg on Sunday, and PW values near two inches in a narrower axis closer to the front. The SPC slight risk area across the north on Saturday, and then throughout the area Sunday, reflect the southward progress of the front, along with the higher CAPE values on Sunday, when the slight risk is area wide. The high PW values, together with the slow moving front, could lead to excessive rainfall over the weekend. A second upper level short wave trough drives a second cold front through the area Monday night, bringing another chance for thunderstorms Monday, again mainly during the afternoon and evening. Temperatures and dew points reflect the soupy summer air mass in place this weekend, with another heat advisory possibly needed for Saturday afternoon, in a similar areas as the current one in northeast KY, southeast Ohio and the southern lowlands of WV. The cold fronts bring a downturn in temperatures and dew points Monday and Monday night, with values getting back to near normal for late July.
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&& .LONG TERM /TUESDAY THROUGH THURSDAY/...
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As of 400 AM Friday... The long term period brings a relief in the heat and humidity, with high pressure providing dry weather through Thursday. A persistent upper level high bulges farthest north over the plains, keeping the upper level flow mainly out of the west northwest, and another system or complex may approach from that direction Thursday night, as the portion of the upper level high over the southeastern U.S. backs off. Highs, lows and dew points will be lowest Tuesday and Tuesday night, in the fresh canadian air, and then slowly moderate to at least normal by Thursday.
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&& .AVIATION /07Z FRIDAY THROUGH TUESDAY/...
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As of 400 AM Friday... Risk for showers increased over the northern 1/2 of the airspace overnight with best odds at KPKB. Increasing mid level clouds btwn 5-10kft should limit visibility restrictions to AOA MVFR. The latest model guidance is more bullish on thunderstorms this afternoon and have started to show this trend via VCTS in 21/06z TAFs. Brief periods of sub-VFR conditions are likely in heavy downpours. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z SATURDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Fog development will depend largely on amount of cloud cover. 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. DATE FRI 07/21/17 UTC 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 EDT 1HRLY 02 03 04 05 06 07 08 09 10 11 12 13 CRW CONSISTENCY H H M M M M M H H H H M HTS CONSISTENCY H H M M M M M H H H L M BKW CONSISTENCY H H H H H H H H H H H M EKN CONSISTENCY H M M M M L L M H H H L PKB CONSISTENCY H H M M M M M L H H H L CKB CONSISTENCY H M M M M L H M L H M L AFTER 06Z SATURDAY... IFR possible Saturday in showers and thunderstorms.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...Heat Advisory from noon today to 7 PM EDT this evening for WVZ005>008-013>015-024>026. OH...Heat Advisory from noon today to 7 PM EDT this evening for OHZ083-086-087. KY...Heat Advisory from noon today to 7 PM EDT this evening for KYZ101>103-105. VA...None. && $$ SYNOPSIS...TRM/99 NEAR TERM...99 SHORT TERM...TRM LONG TERM...TRM AVIATION...99

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