Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 161834 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 234 PM EDT Mon Oct 16 2017 .SHORT TERM...
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(This evening through Tuesday night) Issued at 234 PM EDT MON OCT 16 2017 A sprawling area of surface high pressure from the southern plains into the OH valley will control our weather through Tuesday night. The forecast issue of the day is the frost possibility tonight and Tuesday night. Once the broken cloud deck currently over the area scatters out and winds diminish, tonight will be a good night for radiational cooling. However dewpoints are currently in the upper 30s to lower 40s, as are dewpoints well upstream over OH and IN. Based on latest guidance, blended data and upstream dewpoints it doesn`t appear dewpoints will be able to come down much more as we head into evening. Would really like to see lower dewpoints at this point, as it appears there may end up being more fog than frost especially where more rain occurred yesterday into last night. While there may be a few spots that see some very light frost, most of the area will not see any frost. After collaboration with neighboring offices have decided to not issue a frost advisory for any of our counties. Will issue a Special Weather Statement to cover isolated frost possibility and the locally dense fog possibility for tonight. Even as we head into Tuesday night, with another day of dry weather it still appears dewpoints will not be much lower than today, so only some patchy light frost will again be possible Tuesday night. .LONG TERM...(Tuesday night through Sunday) Issued at 300 AM EDT MON OCT 16 2017 Persistent and strong upper level ridging will remain in place across the eastern US through the remainder of the upcoming week and likely through next weekend. This will continue to support a slow warming trend through the week as warm air builds under the ridge. Tuesday night is still looking the coldest night of the week for the valleys with coop guidance showing some potential for readings as low as 34 degrees. The 12z guidance actually had a 32 degree reading. Thus, going to shoot for some low to mid 30s in the eastern valleys. This should be good enough for at least some patchy frost. The frost extent will be highly dependent on how low dewpoints mix out on Tuesday. Based on the forecast, hard to go with much more than patchy frost again, and mainly in the eastern valleys once again. Hunch is guidance may still be a bit high on those dewpoints and if we mix out better, than frost would be a bigger concern. Either way, eastern valleys appear to see the greatest threat of any frost. Still possible we see some mid 30 temperatures Wednesday night, but with dry air firmly entrenched by then, not sure we will be able to squeeze out must frost and aerial extent of valley fog will start to be more reduced. Will continue to go with modest ridge/valley splits through Saturday night. Also, plan to continue to go on the warm side of guidance for highs given the 1000-500 mean level RH remains under 25% for the entire week and next weekend. Dewpoints each afternoon, are probably not low enough, but at least trended towards drier afternoons as well. We will likely see RH`s under 25 percent from Wednesday afternoon through at least Saturday. Fortunately, as long as high pressure dominates, winds won`t be a concern and fire weather concerns should remain low.
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&& .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) ISSUED AT 123 PM EDT MON OCT 16 2017 High pressure building into the area will bring an extended period of fair weather. For the rest of today, a broken deck of stratocumulus around 4500 feet will scatter out late this afternoon. North winds will continue to gust to around 15 knots this afternoon before diminishing to light and variable this evening. Some valley fog is expected to develop after 06z tonight and may become dense in a few locations. Most of the TAF sites should remain MVFR or better, with the exception of SME which is forecast to drop to IFR. Any fog will burn off Tuesday morning, with VFR conditions for the remainder of the day. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...SBH LONG TERM...KAS AVIATION...SBH

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