Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 230531 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 1231 AM EST Thu Feb 23 2017 .SYNOPSIS... Unseasonably warm weather returns again Thursday and Friday. A strong cold front crosses first thing Saturday morning, followed by cooler weather for the weekend. && .NEAR TERM /THROUGH TODAY/... As of 1000 PM Wednesday... Clearing has worked in along and south of I64 corridor and as one would expect the fog has filled the void. Not sure how much farther north in WV this clearing makes it though. As of 645 PM Wednesday... Much of the shower activity has pushed east of the area at this hour. In its wake are lingering pesky low stratus clouds. As the low level flow turns more SW tonight, expect improvement in cloud bases. However...the fog versus cloud battle will make for a low confidence forecast tonight. Given the wet grounds...low dewpoint depression...and weak flow initially, suspect areas of dense fog will form in any breaks in cloud cover. This is rather difficult to pin down in the grids, though, given the lack of definitive clearing across the area. The low level flow does strengthen a bit toward morning along with the potential for weakly forced showers to break out along and W of the Ohio River with lowering cloud bases once again. As of 3 PM Wednesday... Wave was quickly exiting the area this afternoon, taking the last of the rain with it. Stratocu is likely to linger tonight, limiting fog formation but still do expect some. Thursday will bring a continuation of south to southwest flow with low level moisture remaining in place. Heating is forecast to increase CAPE to 500-700 J/KG. This, along with weak shear, could give rise ton a few thunderstorms as a weak upper level short wave trough crosses in west to southwest flow, but nothing organized is expected. Temperatures close to a blend MET/MAV and bias corrected consensus. && .SHORT TERM /TONIGHT THROUGH SATURDAY/... As of 310 PM Wednesday... Models continue to slow down frontal passage. Latest ECMWF and NAM guidance having the front near the Ohio River by 12Z Saturday and the GFS continues to bisect WV with the front by that time. I have held off on PoP until a few hours later than previous forecast, with Categorical PoP in the Ohio Valley between 6Z - 7Z, but this may still be a bit early. The main concern with this front will be the possibility of isolated damaging wind gusts in convection. Overall, instability is rather weak, with NAM and GFS indicating anywhere from 300 to 600 J/Kg of CAPE with the highest values in the Ohio Valley. However, wind shear values are very impressive with 65 to 70 knots of 0 - 6km bulk shear. Also, upper trough turns slightly negative as it crosses the region and 700mb to 500mb lapse rates increase to 8C/km. It is possible that we could see a weakening QLCS entering the Ohio Valley by early Saturday morning. With the impressive wind shear and modest instability in the Ohio Valley, there is a chance that convection could bring some strong wind gusts down to the surface. With the overnight timing of the front though, the threat for damaging winds will be low, but isolated damage and power outages will be possible in the Ohio Valley and that threat will decrease heading east across West Virginia. The cold front clears the area on Saturday and strong cold air advection pushes in behind it. There may be enough lingering moisture with the upslope NW flow behind the front that the mountains squeeze out a few snow showers. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... As of 315 PM Wednesday... Start off the long term with high pressure over the region, but this will be short lived as zonal pattern is set up across the U.S. Guidance is in a little better agreement with southern stream wave pushing across the area on Monday. This will be the first of what looks like several systems moving through the progressive pattern next week. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... As of 1230 AM Thursday... Could not state the forecast any better than the previous shift, so here it is: A low confidence aviation forecast tonight given the battle waging between stratus and fog formation. I feel fairly confident on CIGS improving as the evening progresses given the low level flow turning more southwesterly. Given the amount of low level moisture in place combined with low dewpoint depressions and a wet ground...any place could fog pretty quickly this evening if there are any substantial breaks in the clouds. I`ve allowed for some IFR vsby in fog to develop where some breaks in the clouds are more likely to occur, from HTS- CRW-EKN. Some weakly forced showers may develop toward morning along and west of the Ohio River which will bring CIGS down once again into MVFR and possibly IFR across southeast Ohio through 15Z. These showers will tend to lift northeast as the day progresses, however, chances are too small to include in TAFs attm. Otherwise expect some 3 to 4 thousand foot stratocu across the area through the afternoon. Surface flow will be light south beneath light to moderate southwest aloft. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z FRIDAY... FORECAST CONFIDENCE: Low tonight. Medium for Thursday. ALTERNATE SCENARIOS: Dense fog may be more prevalent should clouds break more 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. DATE THU 02/23/17 UTC 1HRLY 03 04 05 06 07 08 09 10 11 12 13 14 EST 1HRLY 22 23 00 01 02 03 04 05 06 07 08 09 CRW CONSISTENCY M M M M L L L L L M M L HTS CONSISTENCY L L L L L L L L L L L L BKW CONSISTENCY M H M M M M M M M M M L EKN CONSISTENCY H H H H M L L L L L M L PKB CONSISTENCY H H H H M M H M M M H L CKB CONSISTENCY H H H M M M M H M M M L AFTER 06Z FRIDAY... No widespread IFR conditions are expected at this time. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...TRM/MPK NEAR TERM...TRM/30 SHORT TERM...MPK LONG TERM...MPK AVIATION...30/JW

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