Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 232011 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 411 PM EDT Wed May 23 2018 .SHORT TERM...
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(This evening through Thursday night) Issued at 411 PM EDT WED MAY 23 2018 As of mid afternoon, an upper level ridge of high pressure extended from the eastern Gulf of Mexico and Florida northwest into the MS Valley. At the surface, an area of high pressure was centered over the Great Lakes region. Meanwhile the boundary that crossed the area last night continues to push farther southeast and east of the area and extended from the mid Atlantic states into the Appalachians and then west into the TN and MS Valley regions. Cumulus has gradually been mixing out this afternoon as drier air continues to advect into the region. The axis of the upper level ridge is expected to approach the area from the west through Thursday. Meanwhile surface high pressure will remain in control tonight. With the high in place, temperatures should reach the mid to upper 50s in the valleys or a few degrees below current dewpoints. In addition, the ground is rather moist from recent precipitation. With clearing skies and light winds, the stage should be set for valley fog formation tonight. In the deeper eastern valleys and river valleys, this fog should become dense overnight. This fog should lift and dissipate through 9 to 10 AM. Meanwhile, the surface high is expected to move east and be centered along the mid Atlantic to northeast US coast by the end of the day. As this occurs, moisture is expected to return north especially closer to the crest of the Appalachians as suggested by guidance. Some cumulus development is expected in all areas, but locations further north and west should generally be capped by the drier airmass in place. Despite weak forcing, sufficient moisture should return for mainly isolated showers and even a thunderstorm to develop near the VA border generally after 1 PM. The GFS and NAM both develop convection in the vicinity of Harlan county and some recent convective allowing model runs also develop convection in this area. Outflows from the convection could lead to activity as much as a couple of tiers of counties north into the southeast KY. Any showers and thunderstorms should wane on Thursday evening. Some valley fog should again develop Thursday night, however, dense fog is expected to have less of an areal extent. .LONG TERM...(Friday through Wednesday) Issued at 347 PM EDT WED MAY 23 2018 The upper level reveal the ridge will be in the process of breaking down as a upper level wave develops across the Upper Midwest. This will continue to weaken the ridging and bring more a shortwave pattern into the region. Then we turn our attention to a developing tropical system in the Gulf of Mexico. Surface wise we will see a surface high that was across the Ohio Valley depart to the east By Friday allowing more moisture to spill back into the region. This added moisture and eventual interaction with shortwave energy will keep the region under the potential for mainly afternoon and evening showers and thunderstorms. The best chances through the period will generally be closer to the higher terrain. The aforementioned tropical system will play a role in how much moisture we will receive and this will be dependent on the track and overall evolution. That said, the GFS operational solution is a outlier compared to the ECMWF, Canadian, and most of the GEFS solutions, with its more eastern track. The better overall plume of moisture seems to setup across the Carolinas. Either way it does seem like a increase in moisture could at least lead to isolated heavy rain issues given the potential for afternoon convection each day.
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&& .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) ISSUED AT 215 PM EDT WED MAY 23 2018 Cumulus generally between 3 and 5kft were observed across the region at issuance time, with VFR prevailing. Generally VFR should prevail for much of the period with high pressure in place across the region. The only caveat will be fog development generally after 5Z. The fog should dissipate in all areas by 14Z. However, this fog should become dense in the deeper valleys and river valleys. For the TAF sites, some MVFR reductions are anticipated between 8Z and 13Z at all sites other than SYM. Winds should remain light and variable through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JP LONG TERM...DJ AVIATION...JP

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