Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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227 FXUS63 KJKL 182018 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 418 PM EDT Sat May 18 2024 .KEY MESSAGES... - Dry weather expected area wide from Sunday through Tuesday night. - Rain chances ramp back up Wednesday into Saturday. - Warm weather will be the story Sunday through Wednesday, with afternoon highs topping out in the mid to upper 80s. && .SHORT TERM...(This evening through Sunday night) Issued at 417 PM EDT SAT MAY 18 2024 A very slow eastward moving, positively tilted upper trough lies overhead late today. Drying aloft is making its way in from the north as the trough advances. This is helping to limit convection. Extensive clouds in the south also limited heating/destabilization and have helped to hold back convection there, despite greater deep moisture as compared to the north. As the trough continues heading east and heating is lost, any remaining precip will die out tonight. Much drier air aloft and clearing skies will allow for good radiating conditions. Meanwhile, only slightly drier surface air will try to advect in on weak north to northeast flow. The combination will favor fog development. Will expect it to be abundant in valleys, growing in breadth and depth with time during the night. As heating occurs on Sunday morning, the fog will dissipate and likely transition to a rising cu deck. Although forecast soundings show development of weak mixed layer CAPE which is deep, it is a skinny profile in an extremely dry atmosphere aloft. Without upper level support, it`s unlikely that convective columns will be able to persist and develop precip, and a dry forecast is being used on Sunday. The same regime aloft carries through Sunday night. With cu drying up and giving clear skies, along with weak low level flow, valley fog will again develop. However, after good mixing and a bit more drying during the day Sunday, the fog should be a little more restricted. .LONG TERM...(Monday through Saturday) Issued at 338 PM EDT SAT MAY 18 2024 The period begins with shortwave ridging extending into the Northeast states. This ridging will keep the weather quiet and warm through mid week ahead of an advancing cold front, with good agreement noted in the ensembles and deterministic guidance. The afternoon high temperatures Monday and Tuesday are forecast to climb into the mid to upper 80s. By Wednesday, we see the leeside low that develops Monday night will be pushing northeast into the Great Lakes and Canada by Tuesday night. While there are slight differences in the guidance during this period the overall pattern looks fairly close. It gets a little trickier across the Ohio Valley going into mid- week. This is because the various ensembles and deterministic are struggling on how far south and east this cold front can go given it looses the greater upper level support and the low pressure pushes northward further into Canada. Right now, it looks like the diffuse cold front would arrive Sometimes Wednesday night into Thursday. This would usher in better chances of showers and thunderstorms, with around a 20-40 percent chance Wednesday and 50-60 percent chance Thursday. Now there have been some indication in machine learning products of severe weather potential with this system. If this was to occur it would be late Wednesday into Wednesday night before better storms arrive based on the latest trends. However, confidence is low given the better shear and instability stay northwest of the area. Past this the guidance becomes more divergent, but it looks like another mid-level shortwave rides in Friday. This would lead to a renewed chance of showers and thunderstorms going into the weekend, as an area of low pressure forms along the left over boundary mentioned above. The best chances of showers and thunderstorms right now would be Friday at 50-60 percent. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 238 PM EDT SAT MAY 18 2024 A mix of VFR and MVFR conditions (due mainly to ceilings) were present at the start of the period. While most showers present during the morning had dissipated, renewed development with daytime heating/destabilization was starting. A general improvement to VFR is expected by late afternoon as ceilings continue to rise. However, additional development of showers and possibly thunderstorms will lead to localized sub-VFR conditions in the heavier precipitation. The showers and thunderstorms will die out this evening and most clouds will dry up. Good radiating conditions will lead to development of valley fog late tonight. It will grow in breadth and depth through dawn, but exactly how widespread it becomes is uncertain. At this point, the best estimate is that TAF sites will be IFR at least at times. The fog will dissipate early Sunday morning, leaving VFR conditions through the end of the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...HAL LONG TERM...DJ AVIATION...HAL