Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 221840 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 240 PM EDT Sat Apr 22 2017 .SYNOPSIS...
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Upper disturbance exits later this afternoon with most of the rain...but stationary frontal boundary just south of the area will keep a rain threat mostly across the south and east through the remainder of the weekend.
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&& .NEAR TERM /THROUGH TONIGHT/... As of 1145 AM Saturday... Looks to be the eastward moving short wave over western parts of the area at time will be the main player this afternoon. Hi res models and radar picking up on this and indicate a break in the widespread precip behind this feature from west to east. However, with the frontal boundary hanging just south of the area, will maintain higher pops in the south behind this feature this afternoon. Any thunder will be confined to the far south this afternoon closer to the frontal boundary. Otherwise, rain will be winding down from at least the I64 corridor northward as both the short wave exits and drier air filters down from the north into these area this afternoon. Will continue the current Flash Flood watch for the southern mountains with continued higher pops. 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 SATURDAY/... 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 /18Z SATURDAY THROUGH THURSDAY/...
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As of 200 PM Saturday... Improving conditions spreading south and east this afternoon and tonight as upper disturbance shifts eastward across the area, allowing drier air to filter in from the north. MVFR/IFR in widespread rain and an isolated thunderstorm ahead of the upper disturbance this afternoon, particularly across southern and eastern West Virginia and southwest Virginia. Improvement to VFR ceilings AOA 4000 feet by 00Z across southeast Ohio and northwest WV, including PKB, behind the disturbance. Northerly winds 8 to 13 MPH. VFR ceilings works slowly south and east 00Z-03Z into central WV by 06Z, reaching CKB by 02Z, but remaining just north of a HTS- CRW-EKN line for the remainder of the night. MVFR ceilings continue south of this line; except IFR in the southern mountains, including BKW, where a continued rain threat exists with frontal boundary stalled just to the south. Winds becoming easterly at 5 to 10 MPH. For Sunday, an upper low tracks to the south and then east of the area, spreading rain back to the north and east. However, most of the rain will be in the mountains. Winds southeast 5 to 12 MPH. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z SUNDAY... FORECAST CONFIDENCE: Low to medium. ALTERNATE SCENARIOS: Improving conditions may be faster and farther south later this afternoon and tonight over the northwestern half of WV, southeast Oh and northeast KY. 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 18 19 20 21 22 23 00 01 02 03 04 05 EDT 1HRLY 14 15 16 17 18 19 20 21 22 23 00 01 CRW CONSISTENCY M M L L L M M M M M M L HTS CONSISTENCY M M M M M M M M M M M L BKW CONSISTENCY M L M M M L L L L L L L EKN CONSISTENCY L M M L L L L L M M M L PKB CONSISTENCY M M M M H H H H H H H M CKB CONSISTENCY H M M M M M M M H H H M AFTER 18Z SUNDAY... IFR possible Sunday into Monday with another wave of low pressure.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...Flash Flood Watch through Sunday evening for WVZ033-034. OH...None. KY...None. VA...Flash Flood Watch through Sunday evening for VAZ003-004. && $$ SYNOPSIS...TRM/JMV/SL NEAR TERM...JMV/SL SHORT TERM...TRM LONG TERM...TRM AVIATION...JMV is the U.S. government's official web portal to all federal, state and local government web resources and services.