Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 200807 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 400 AM EDT FRI MAY 20 2016 .SYNOPSIS...
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Low pressure approaches today and moves through tonight...then shifts to our southeast on Saturday. Heavy rain threat exists late today into this evening mostly for Ohio River Valley counties.
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&& .NEAR TERM /THROUGH TONIGHT/...
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At 0730z...southeast wind flow increasing with lower clouds trying to form along the eastern slopes. In the cool air...patches of fog did form mostly in the colder sheltered mountain valleys. Precipitable water jumps from around .5 inches at 06z to 1.5 inches in nrn Ky and se Ohio bfr 00z Saturday. Still concerned about a flash flood threat...but mostly in our western counties after 20z today and lifting ne this evening. This includes ne Kentucky...se Ohio and the mid Ohio Valley counties of WV. The 00z nam had the 850 mb flow increasing from 15 to 20 knots at 21z to 40 to 45 knots by 03z. Impressive. At least...there is not a strong temperature gradient for that flow to act on. The best 850 mb moisture convergence should lift northeast today toward Sdf- Cvg-Lex vcnty by 21z this aftn...then into the Uni-Hts-Pkb corridor by 00z to 03z this evening. Rain amounts around 1.3 to 1.5 inches in 3 hours would start to get us concerned...but the new spring vegetation is helping. Will not hoist a flash flood headline with the predawn morning package but we will continue to revisit this threat today. Mentioned the heavy rain and embedded thunder in the area with best support. Will highlight the counties we feel are most vulnerable in our hazardous weather outlook. Thinking the southeast flow will help shield the Crw to Buckhannon and Elkins...and maybe even Ckb from the heaviest rain. A secondary rain max may be along the eastern slopes including Pocahontas County overnight. Have moisture at 4 to 8 thsd ft increasing in southern West Virginia this morning and spreading north. Warmest maximum temperatures inserted toward Ckb-Buckhannon-Ekn. Counting on thicker clds and pcpn arriving to hold Hts vcnty temperatures down a bit this aftn. The biggest change in our hourly pops was to bring lowering pops into our southwestern counties faster overnight...as the support lifts into eastern Ohio and western Pennsylvania overnight after 06z.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY/...
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Main swath of 850mb Theta E convergence will have lifted well to the northeast of the CWA by Saturday morning...so the short term will be primarily dealing with the upper trough at 500mb with the extra lobe dropping in from the north for Saturday night. By and large...this will end up as the cold pool convection period as the surface low regenerates along the mid atlantic coast and the aforementioned 500mb low all but stalls over the Delmarva Peninsula. In the forecast grids...this has necessitated an increase of the POPS back to the west for Sunday to low end chance that will peak with the heating of the day. Could be difficult to get rid of the isolated showers over the northeast mountains because of the behavior of the upper level low...so those low chances will outrun the lowlands from a time standpoint...lingering into Monday...as high pressure tries to regain control. Temperatures continue to be held in check given the lowering heights...with slightly below average values across the board.
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&& .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... SFC high pressure will push into the region for the start of the new work week. This will give us some dry and warm conditions through at least mid week. Guidance is indicating a stationary boundary drifting over the region by Wednesday or Wednesday night and this will not move much through the end of the week. Several transitioning shortwaves will bring the threat for showers and thunderstorms into Friday. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/...
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Lowered confidence to medium. Coverage of the predawn fog at EKN...CKB...PKB...and CRW in question...as high clouds increase and the flow/wind at 925 mbs also increases. With the increasing flow...did not take lowlands down in any thick fog before dawn. Mountain valleys may be sheltered and cool enough for pockets of ifr. Moisture/clouds at 4 to 8 thsd ft should increase over southern WV 06z to 14z...and spread north today...lowering further over the eastern slopes. On the 00z nam...the strongest 850 mb moisture convergence lifts out of western Tennessee early today...through central Kentucky...and into southeast Ohio this evening. Will have ceilings and vsby lowering in the hts-uni-pkb corridor before 00z. with that support...also included embedded thunder in ne Ky...Hts vcnty and se ohio...but not in any specific taf forecast at this distance. Figuring the southeast flow will keep Crw to Ekn in better shape in the rain showers. In contrast...the same southeast flow should lower ceilings after 23z in the eastern slopes including the Bkw vcnty. FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Coverage and thickness of the predawn fog in question with increasing boundary layer winds. 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 05/20/16 UTC 1HRLY 08 09 10 11 12 13 14 15 16 17 18 19 EDT 1HRLY 04 05 06 07 08 09 10 11 12 13 14 15 CRW CONSISTENCY M M M H H H H H H H H H HTS CONSISTENCY H H H H H H H H H H H H BKW CONSISTENCY H H H H H H H H H H H M EKN CONSISTENCY L L L M H H H H H H H H PKB CONSISTENCY H H H H H H H H H H H H CKB CONSISTENCY H H H H H H H H H H H H AFTER 06Z SATURDAY...
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...KTB/26 NEAR TERM...KTB SHORT TERM...26 LONG TERM...MPK AVIATION...KTB

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