Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 212335 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 735 PM EDT Mon Aug 21 2017 .SYNOPSIS... High pressure continues into Tuesday. Strong cold front late Tuesday into Tuesday night. Cooler and drier high pressure into the weekend. && .NEAR TERM /THROUGH TUESDAY/...
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As of 730 PM Monday... Tightened up POP gradients tomorrow, keeping things more isolated through mid day, then ramping up quickly along the cold front as it moves in from the west late afternoon into evening. As of 210 PM Monday... Mainly dry except in the north where a few isolated showers are possible this afternoon and evening. High pressure lingers into Tuesday, but then a well defined system translates through Tuesday evening. All indications suggest that there could be some severe weather with this frontal system though believe it will be north of the I-64 corridor. Ample moisture, upper and low level forcing, and wind shear all provide a favorable atmosphere for storm development and maintenance. Veering wind profiles also suggest some potential for rotating storms. Timing of the system, with the front moving through in the late afternoon, is just about right for maximum realization of CAPE. PW`s are also quite high in the 2.5" arena, so heavy downpours will also accompany these storms. Luckily they should have enough forward propagation that only local water issues may result. For now, gusty outflow from cells looks like the largest threat with damaging winds possible. The tornado and flash flooding threats are fairly low, but non-zero.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 350 PM Monday... As has been described with previous forecast issuances, this system will feature two distinct surface fronts. The initial front will be the focus of convection and will be located near the Ohio River by 8 PM Tuesday. Severe potential will be waning with the loss of daytime heating and instability, though precip loading from heavy downpours combined with momentum transfer of upper level winds can still generate occasionally strong gusts overnight. This front will clear the CWA by day break Wednesday. The secondary front, behind which lies the much-anticipated Canadian airmass, will move through the eastern mountains by the end of the day Wednesday. Scattered redevelopment of showers and perhaps storms along the front in the WV mountains and southwest VA is likely during the Wednesday afternoon hours. Meanwhile, the remainder of the area outside of the mountains will enjoy high temperatures 5-10 deg F below normal with comfortable dewpoints in the 50`s under the full influence of deep northwest flow. && .LONG TERM /THURSDAY THROUGH MONDAY/... As of 350 PM Monday... The region will be under the influence of deep northwest flow to start the period. Easterly low-level flow from the Atlantic in the Piedmont will provide some low-level moisture for disturbances embedded within NW flow to potentially drum up showers in the mountains during the weekend. Areas west of the mountains will enjoy persistent dry northeasterly surface winds. This synoptic pattern will hold while the parent closed upper- level low struggles to exit eastern Canada. At the very end of the forecast period, long- term models indicate an embedded short- wave developing a surface system to increase precipitation chances to start the work-week. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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As of 730 PM Monday... Cirrus on the increase overnight into Tuesday morning. This, and some flow should keep dense fog out of most areas. Did include some IFR at EKN in the deeper valley and with the thinest clouds. Isolated thunderstorms will develop Tuesday afternoon ahead of a cold front. These should drive from SW to NE. Included VCTS due to uncertainty with location and timing. Stronger and more organized storms expected late afternoon into the evening as a cold front pushes in from the west. Would expect brief drops into IFR as these move from west to east into Tuesday night. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z WEDNESDAY... FORECAST CONFIDENCE: High. ALTERNATE SCENARIOS: May have pockets of denser fog tonight. Main line of storms with cold front Tuesday evening could arrive a bit earlier than forecast. 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 H M M BKW CONSISTENCY H H H H H H H H H H M M EKN CONSISTENCY H H H H H H H H M M L L PKB CONSISTENCY H H H H H H H H H H M L CKB CONSISTENCY H H H H H H H H H H M M AFTER 00Z WEDNESDAY... IFR possible in showers and storms Tuesday night. IFR possible in low stratus and showers/fog into early Wednesday. River valley fog possible each morning through the weekend.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...JW/MC NEAR TERM...JW/MZ SHORT TERM...MC LONG TERM...MC AVIATION...MZ

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