Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 182234 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 634 PM EDT Tue Jul 18 2017 .SYNOPSIS... Upper ridge dominates the work week, with increasing heat and humidity, and mainly scattered afternoon mountain storms. Storms increase with northwest flow Friday into the weekend. && .NEAR TERM /THROUGH WEDNESDAY NIGHT/...
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As of 630 PM Tuesday... Bumped up hourly temps for the next few hours to account for observed temps/trends. Spotty ridgetop convection continues in mountain counties with heavy rain and gusty winds possible. Convection will diminish after 00Z with the loss of solar heating. Rest of forecast on track. As of 140 PM Tuesday... No significant changes necessary to the previous forecast. Upper ridge across central U.S., gradually building east into the region, with an upper trough/low just to our east. Showers and thunderstorms have started to develop along higher terrain and east of mountains, as southeasterly upslope flow/differential heating take hold. There has also been isolated showers developing across parts of southeast Ohio in vicinity of a stalled boundary. As with Monday, convection should dissipate after sunset, for another warm, muggy night, with river valley fog. Any fog will burn off early tomorrow morning, with increasingly warm conditions as upper ridging starts to nudge east into the region. Temperatures on Wednesday should max out a couple of degrees higher than today.
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 345 PM Tuesday... Period begins dry with upper and lower level ridging. The upper ridge is an eastward extension of a large upper level high over the central plains and separates an upper level low over the mid Atlantic, and the westerlies across the northern tier of the U.S. Meanwhile, low level southwest flow between the surface high nearby, and low pressure over the midwest, will be feeding into a warm front setting up from that low, eastward and then southeastward into the upper Ohio Valley. It is along this boundary and the ring of fire that thunderstorms complexes will be riding, once initiated upstream where the best low level feed resides. One such complex approaches Thursday but will likely fall apart as it reaches far northern portions of the forecast area, as it gets well downstream of the best feed, and morning and midday cloud top warming occurs. The next complex approaches overnight Thursday night into Friday morning. This one has a chance to make better in roads into northern portions of the forecast area Friday, on account of its earlier timing, and its initiating upstream feed being a little closer. That feed breaks down in favor of another one farther upstream, allowing weak surface high pressure to build in Friday night. Temperatures and dew points reflect the very warm and humid summer air mass in place. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 345 PM Tuesday... Forecast area will reside along the southern edge of the westerlies most of the period. The upper level flow gradually backs from west- northwest to west-southwest Saturday through Monday, as broad upper level ridging crosses, but with embedded smaller scale short waves trough moving through. At the surface, high pressure Saturday morning gives way to southwest flow, as a front and larger upper level short wave trough, slowly approach from the west. The chance for thunder in the area will be tied mainly to daytime heating on Saturday, and then most persistent across northern portions of the area Saturday night. The southeast end of the warm front will be more like a stationary or wavering front, its position crucial in determining where convective complexes track, or vice versa per meso scale outflow boundaries. While model differences exist on the timing of the arrival of the cold front heading into next week, the chance for showers and thunderstorms increases with its approach Sunday, and then decrease with its passage. Models also diverge on whether a wave holds the front up or even pushes it back northward for a time, on or about Monday. Chance PoPs on Day 7, Tuesday, reflect the forecast projection time during this time of year, and increasing model uncertainty at that range, in light of the uncertainty with the front Sunday and Monday leading up to that time. Temperatures and dew points reflect the very warm and humid summer air mass in place, before returning closer to normal, at least on highs, Monday and Tuesday, on account of the effects of the front. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
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18Z Tuesday thru 18Z Wednesday... As of 630 PM Tuesday... Convection ongoing in the mountains, generally to the east of KEKN/KBKW. Cannot rule out brief VCTS through 00Z, but activity will diminish thereafter. Rest of forecast on track with predominant VFR conditions through 19/04Z, then areas of IFR valley fog possible until around 19/13Z. As of 140 PM Tuesday... Light winds and mainly VFR conditions through 05Z. Isold convection possible through 01Z, mainly across southeast Ohio and the mountains, with brief MVFR or IFR conditions possible. Otherwise, after 05Z, patchy river valley fog with IFR conditions possible again, particularly at sites along the Ohio River. Any fog will dissipate 12-13Z for a return to VFR conditions. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z THURSDAY... FORECAST CONFIDENCE: Medium for fog tonight. Medium for northern/central WV mountain convection this afternoon. ALTERNATE SCENARIOS: Fog timing and extent will likely vary tonight. 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 22 23 00 01 02 03 04 05 06 07 08 09 EDT 1HRLY 18 19 20 21 22 23 00 01 02 03 04 05 CRW CONSISTENCY H H H H H H H H H H M M HTS CONSISTENCY H H H H H H H H H M L L BKW CONSISTENCY H H H H H H H H H H M M EKN CONSISTENCY H H H H H H H H H M L L PKB CONSISTENCY H H H H H H H H M L L L CKB CONSISTENCY H H H H H H H H H H M L AFTER 00Z THURSDAY... Patchy IFR river valley fog is possible Thursday and Friday mornings.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...TRM/SL NEAR TERM...SL/DTC SHORT TERM...TRM LONG TERM...TRM AVIATION...SL/DTC

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