Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 221026 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 626 AM EDT Sat Apr 22 2017 .SYNOPSIS... Low pressure passing south of the area brings widespread rain today. This rain becomes increasingly confined to the mountains tonight and Sunday. The low pulls away early in the work week. && .NEAR TERM /THROUGH TONIGHT/... As of 430 AM Saturday... Wet weather in the near term period. Initial wave moves through this morning, generally exiting the area by 10Z. Generally light precipitation is associated with this initial wave. However, this will be followed by another wave, with a band of heavy precipitation, moving into the CWA around 15Z, before exiting later this afternoon and evening. Models are in decent agreement concerning the timing and location of axis of heavier precipitation this afternoon with this wave, currently visible on radar across southeast MO and western KY, and creating flooding concerns across aforementioned areas this morning. At this point, should be a brief break later this evening after the second wave exits, but pops will increase again towards the end of the period, particularly across southern zones, as low pressure system moves east along stalled frontal boundary just south of CWA towards our region, spreading more precipitation back into the area. Could see the possibility of the FFA being expanded across eastern zones in the future, but for now, there is still a bit of uncertainty as to where the axis of heavier precipitation will set up. Regardless, it looks like after the second wave passes today, there will be a stark difference between northern zones i.e. southeast Ohio and adjacent counties, and southern zones, which will remain overcast and in higher moisture content air. For now, with the location of the frontal boundary, and higher confidence in heavier precipitation, have elected to issue a flash flood watch across southwest VA and McDowell and Wyoming counties, with the possibility it will need to be expanded in future updates.Area of showers incoming from the south. Reworked POPs to better reflect timing on these as they head NE. && .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... As of 430 AM Saturday... Low pressure system becomes stacked as it tracks south of the area Sunday through Sunday night. Southeast portions of the forecast area will be closest to the wheelhouse of this system, with frontogenetic forcing beneath diffluent flow northeast of the upper level low and at the mouth of deep layer southerly flow. Have an inch Sunday extreme southeast portions of the forecast area, and then generally one-half inch amounts up and down the mountains Sunday night. As the system slowly pulls away Monday and Monday night, high pressure anchored over New England, and low pressure over the upper midwest, combine to configure a cool air damming wedge, resulting in moist upslope flow along the eastern slopes of the mountains. This will keep that area socked in with low clouds and light rain and drizzle. This pattern gradually breaks down Tuesday on account of the pressure gradient from the low to the west moving in, resulting in a southerly flow. Farther west, the middle Ohio Valley may turn out mostly dry depending upon where the western edge of the rain shield sets up. There was good model agreement on this being just east of the Ohio River. There may be an odd potpourri of low clouds and fog in a light pressure gradient Monday night. The southerly flow that develops ahead of the low approaching from the midwest may prevent a widespread dense fog event in the wake of the exiting system Tuesday night. No changes needed to central guidance temperatures as models are consistent in time and with each other on the synoptic scale. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 430 AM Saturday... A weak cold front approaches Wednesday and then crosses Wednesday night. The southerly flow ahead of it is expected to bring enough return moisture northward to combine with sufficient shear for afternoon and evening thunderstorms. The front falls apart Thursday, and a warm, more humid southerly flow becomes re-established. A new wrinkle introduced to the forecast for Friday is yet another weak upper level short wave trough approaching from the west. This one does not so much have a surface reflection in terms of a cold front, but the upper level disturbance, combined with instability and shear, could be enough for afternoon and evening thunderstorms. The GFS omitted this feature in favor of stronger upper level ridging, but this solution was largely discounted by WPC given the convergence of the Canadian and the ECMWF, along with the ECMWF and GFS ensemble means. The week should end dry and very warm on Saturday given high pressure up and down the eastern seaboard per WPC and all model solutions. No changes were needed to central guidance temperatures, which have trended slightly lower on Friday given the introduction of clouds and convection to the forecast. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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As of 630 AM Saturday... Initial wave of showers and isold thunderstorms moves across the area through 14Z, with mainly VFR conditions, although brief MVFR and IFR conditions expected in heavier showers, particularly across the mountains, such as at sites KBKW and KEKN. Next wave of heavier precipitation will move east across the area after 14Z. This wave will generate more widespread MVFR and local IFR conditions, particularly in heavier bands. General decrease in precipitation from west to east after 21Z, although widespread MVFR and IFR conditions should linger, particularly across West Virginia and southwest Virginia. Some partial improvement to low vfr is possible across southeast Ohio and adjacent WV sites near to the Ohio River mainly after 06Z, but this is still uncertain, and areas that clear would be susceptible to fog restrictions. Light and variable surface winds during the period. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z SUNDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: More widespread MVFR and IFR conditions may occur than currently forecast. Conditions across southeast Ohio and adjacent sites/counties may not improve to vfr later. 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 10 11 12 13 14 15 16 17 18 19 20 21 EDT 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 CRW CONSISTENCY M M M M M M M M M H L L HTS CONSISTENCY M M M M M M L M H H L L BKW CONSISTENCY H H H M L L L L M L L L EKN CONSISTENCY M M H H H M M L M L L L PKB CONSISTENCY H H H H M M M M M M L L CKB CONSISTENCY H H M M H H H H M H M M AFTER 12Z SUNDAY... IFR possible Sunday into Monday with another wave of low pressure.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...Flash Flood Watch from noon EDT today through Sunday evening for WVZ033-034. OH...None. KY...None. VA...Flash Flood Watch from noon EDT today through Sunday evening for VAZ003-004. && $$ SYNOPSIS...TRM/SL NEAR TERM...SL SHORT TERM...TRM LONG TERM...TRM AVIATION...SL

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