Area Forecast Discussion
Issued by NWS Charleston, WV

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208 FXUS61 KRLX 210443 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 1243 AM EDT Sat Oct 21 2017 .SYNOPSIS... High pressure remains in control, with cool nights and warm afternoons through the weekend. A strong cold front and low pressure system crosses early next week. && .NEAR TERM /THROUGH TODAY/...
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As of 1240 AM Saturday...Temperatures are running a bit cooler than previously forecast with efficient radiational cooling under clear skies and light winds, so dropped low temperatures down a couple of degrees. With temps running a bit lower, there is some concern we will see a bit more fog as we will be much closer to crossover temperatures, but still not enough confidence at this time on what valleys will actually get the fog, so will leave fog forecast as is for now. As of 820 PM Friday... No changes. As of 150 PM Friday... Mainly clear overnight...though cirrus will try to spread into the area toward dawn. Another beautiful warm day Saturday with some passing cirrus. I continue to go a little below guidance for overnight lows, especially in the mountain valleys with near ideal radiational cooling once again. Highs on Saturday were nudged near the warm side of the envelope with 10 t0 15 degrees above average expected.
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&& .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... As of 345 PM Friday... High pressure remains in control with deep southwesterly flow continuing to bring above-average warmth into the Mid-Ohio Valley and Central Appalachia. Low-level cloud cover will begin to build in from the southeast with the approach of a deep trough late Sunday. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 345 PM Friday... A briefly cut-off low will merge again with the northern jet and undergo cyclogenesis in the central to eastern CONUS by the start of the next work week. Models are beginning to hone in on a solution that suggests a storm track through the Ohio Valley though substantial track differences still exist. More expeditious guidance brings rain showers in starting midday Monday, although downsloping would favor a delayed onset until Monday night - closer to a consensus blend of guidance. An even greater delay in rain is possible if cyclogenesis is concentrated further south allowing greater warm air advection to push the frontal zone north. Nevertheless, the forecast depicts an elongated frontal zone passing through the area early Tuesday morning. Though exact frontal position is up for debate, high confidence exists for gusty, widespread rainfall Monday night through Tuesday. Being that cyclogenesis in this case is aided by strong divergence associated with a 120+ kt 300mb jet, and the deepening of this low tightens height gradients through the column, winds are expected to increase first with system onset Tuesday morning and again with the secondary cold front on the back side of the system Wednesday morning. The secondary cold front will usher in the coldest air experienced thus far this season with northwest flow behind. Showers may linger through Wednesday tapering off Thursday under the influence of a brief ridge. Pattern remains active with another trough to round out the week. && .AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
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00Z Saturday thru 00Z Sunday... As of 700 PM Friday... No changes to current forecast as high pressure rules. As of 150 PM Friday... High pressure with VFR mostly clear skies continues. Low level flow should be weaker tonight through Saturday morning, so IFR or worse river valley fog will be possible. However, current thinking is for shallow fog confined tight to the rivers with terminals staying above the fog layer. The exception being EKN where enough agreement in guidance for dense fog late. Look for light south winds Saturday. VFR conditions area wide Saturday amid some passing cirrus. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z SUNDAY... FORECAST CONFIDENCE: Medium overnight. ALTERNATE SCENARIOS: IFR or worse fog could sneak into CRW/PKB in the 11 to 12Z timeframe. 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 SAT 10/21/17 UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 EDT 1HRLY 23 00 01 02 03 04 05 06 07 08 09 10 CRW CONSISTENCY H H H H H H H H L M M L HTS CONSISTENCY H H H H H H H H M M M L BKW CONSISTENCY H H H H H H H H M M M L EKN CONSISTENCY H H H H H H L L M M L L PKB CONSISTENCY H H H H H H H H M M M L CKB CONSISTENCY H H H H H H H H M M M L AFTER 06Z SUNDAY... Dense valley fog possible each morning through the weekend, and in rain at times early next week.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...JMV/30/MC NEAR TERM...JMV/MPK/30 SHORT TERM...MC LONG TERM...MC AVIATION...JMV

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