Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 200656 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 256 AM EDT Thu Jul 20 2017 .SYNOPSIS... Upper ridge over the Ohio Valley weakens, with increasing heat and humidity, and mainly scattered afternoon mountain storms. Convective activity on the increase into the weekend. && .NEAR TERM /THROUGH TODAY/... As of 730 PM Wednesday... No changes necessary. As of 215 PM Wednesday... Isolated showers have developed across the forecast area this afternoon in the moist unstable atmosphere. But overall, threat for showers remains quite low, and any should dissipate by sunset with the loss of heating. Tonight will be similar to previous nights, with a mostly clear sky, and patchy river valley fog developing towards morning. Thursday, strengthening upper ridge and warmer low level temperatures should result in temperatures a few degrees warmer. A shortwave will move east across the Great Lakes late in the day on Thursday/Thursday night, with increasing chances of showers and thunderstorms, particularly across southeast Ohio towards the end of the period. Some of the storms could be on the stronger side, with increasing shear 30-40kts, but overall, better dynamics lie to the north, and timing of storms is late, which should help to mitigate the threat in the near term somewhat. SPC has the area in a marginal risk for storms. && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/... As of 250 PM Wednesday... Weak High pressure will gradually shift southward but continuing to pump warm air and moisture up over the region. A frontal boundary across the Great Lakes will start to sag southward through Friday. This boundary will trigger showers and thunderstorms across the northern portion of the CWA late Thursday night into Friday Morning. As the boundary stalls over the area Friday night, the showers and thunderstorms shifts southward with it. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As of 235 AM Wednesday... Plenty of moisture will be in place as weak frontal boundary stalls and becomes non-existent as ridging starts to build again over the region. However, with any left over boundary, showers and thunderstorms will remain in the forecast through the weekend, especially during peak heating. A cold front is expected to move through on Monday with greater chances for thunderstorms with the front. Warm airmass generally stays in place until the cold front pushes through on Monday. Drier and a tad cooler temperatures on tap for Tuesday and Wednesday. && .AVIATION /07Z THURSDAY THROUGH MONDAY/... 06Z Thursday thru 06Z Friday... As of 200 AM Thursday... Upper ridging continues to weaken. A frontal system over the upper midwest early this morning will drop southeastward today and tonight, but staying just north of our area by 12Z Friday. Today... More widespread MVFR haze/fog for mainly the river valley areas early this morning as compared to yesterday morning, with patchy IFR fog mainly affecting PKB and EKN 09Z- 12Z. Thereafter, generally SCT 5000-7000 feet AGL except becoming BKN far northern portions of area by around 00Z. Models have a mid level dry slot crossing today ahead of the front. Associated convection and deeper moisture with the front is expected to remain mostly north of our area until around 00Z. Thus, will leave convection out of most of the area and the major TAF sites today. Tonight... Even though frontal system sags ever so slowly southward and will remain just north of our area by 12Z Friday, west to northwest flow aloft is expected to carry the deeper moisture and convection southward across the north and into central sections of WV by 12Z Friday. However, despite deep moisture, the diurnal timing will tend to diminish the convection, and will keep the convection as scattered. So, given this uncertainty with the convection, will keep mention out of the northern TAFS of PKB, CKB and EKN for now. Dry south. Generally VFR ceilings 4000-7000 feet across the north, except lower in scattered convection, while SCT mid level clouds prevail in the south. Near calm winds by night, and west winds 5 to 10 KTS by day. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 06Z FRIDAY... FORECAST CONFIDENCE: Medium ALTERNATE SCENARIOS: IFR Fog development early this morning may vary from forecast. Timing and southward extent of convection may also vary. 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 07/20/17 UTC 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 EDT 1HRLY 02 03 04 05 06 07 08 09 10 11 12 13 CRW CONSISTENCY H H M M M M M H H H H M HTS CONSISTENCY H H M M M M M H H H H M BKW CONSISTENCY H H H M M M M H H H H M EKN CONSISTENCY H H M M L L M H H H H M PKB CONSISTENCY M L L L L L M H H H H M CKB CONSISTENCY M M M L L L H H H H H M AFTER 06Z FRIDAY... Patchy IFR river valley fog is possible Friday morning, and Friday and Saturday in showers and thunderstorms. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...JS/SL NEAR TERM...SL SHORT TERM...JS LONG TERM...JS AVIATION...JMV

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