Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 151731 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 1231 PM EST Fri Dec 15 2017 .UPDATE... Issued at 1039 AM EST FRI DEC 15 2017 Updated the forecast to input the latest observations through the the morning hours and trend them into the afternoon. It appears the forecast challenge for the day will be forecasting the departure of the cloud cover today and its impact on the high temperatures. UPDATE Issued at 737 AM EST FRI DEC 15 2017 Fine-tuned the hourly temperatures and dew points through the morning, otherwise the forecast remains on track. && .SHORT TERM...(Today through Saturday) Issued at 353 AM EST FRI DEC 15 2017 Surface high pressure is currently nosed in across the Ohio Valley, with weaker low pressure centered across Lake Superior. Aloft, a trough axis is aligned from the western Great Lakes down to the Desert Southwest. Low level clouds have been persistent across eastern Kentucky overnight, as moisture continues to be trapped at the 925-850mb layer. The trough axis will move southeast across the Ohio and Tennessee valleys today. Heights will then recover aloft tonight into Saturday, as a ridge axis sharpens up across the Mississippi Valley. Low clouds will be hanging around through the morning across most of the area, before some thinning occurs in the afternoon. This will limit the diurnal rise once again, with highs generally in the mid to upper 30s, with perhaps a few 40 degree readings, where places start out milder. Clouds will be on the decrease tonight into Saturday, as the ridge builds in from our west. Lows tonight will range from the low to mid 20s in valley locations, to the upper 20s on the ridges under partly cloudy to mostly clear skies. Saturday will feature a mostly sunny day, with temperatures rebounding to around the 50 degree mark. .LONG TERM...(Saturday night through Thursday) Issued at 328 AM EST FRI DEC 15 2017 The period begins Saturday night with high pressure to our southeast and ridging aloft. Despite the gradient from approaching system to the southeast think the eastern valleys will decouple early and lead to at least a 5 degree ridge/valley split Saturday night. Then we see a southern stream shortwave ride northeast out of Texas and this will bring overrunning precipitation toward the area by Sunday. We continue to see models slowing the progression of this system and therefore have slowed this down further from previous forecast. There was talk of mix precipitation in previous forecast, but given the slower progression this has been removed. The models have also trended drier, as the upper level wave dampens overtime and 850mb jet is fairly weak overall. The better low level jet will be strongest in the afternoon on Sunday leading to more confidence for later onset. We remain in the southwest flow regime through early next week and therefore keep small chances of precipitation each day with lowest POP day being Monday. The next best chance of rain showers will be Tuesday, with the help of a jet streak and shortwave aloft. The flow aloft does flatten out and a surface high progresses east out of the Central Plains to round out the period. This will lead to cooler nights and better shots of seeing ridge/valley splits. Overall afternoon high temperatures will be near to above normal and low temperatures near to above normal. && .AVIATION...
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(For the 18Z TAFS through 18Z Saturday afternoon) ISSUED AT 1231 PM EST FRI DEC 15 2017 Current conditions across eastern Kentucky feature a lingering low level stratocumulus deck that is slowly progressing east across the area. This deck will slowly lift and dissipate by the evening hours as southwest flow engages behind it. Timing this will be the key so will keep MVFR conditions through 22z to 00z at the TAF sites to time this. After this, skies will give away to a cirrus layer and clearing skies heading into tomorrow as high pressure passes through. Expect the winds to remain west and gusting to 20 knots at some place before becoming light and variable by 00z.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...SHALLENBERGER SHORT TERM...GEOGERIAN LONG TERM...DJ AVIATION...SHALLENBERGER

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