Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 211722 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 122 PM EDT Sat Oct 21 2017 .UPDATE...
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Issued at 1111 AM EDT SAT OCT 21 2017 Now that fog has dissipated across the area, a forecast update has been issued with fog removed. The rest of today will feature light winds, mostly clear skies, and dry conditions. The latest obs have been incorporated into the hourly forecast grids as well. UPDATE Issued at 645 AM EDT SAT OCT 21 2017 Issued an update to the grids to input the latest observations and trend them through the morning hours. Also slightly tweaked the amount of fog in the grids as a bit more is present this morning.
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&& .SHORT TERM...(Today through Sunday) Issued at 331 AM EDT SAT OCT 21 2017 The main weather feature through the short term will be high pressure anchored across the central Appalachian range. As this high shifts east, southerly flow will be on the increase bringing ample moisture northward into the region. This apparent even now with upper level moisture in the form of cirrus drifting north over central Kentucky. This will continue into the day today with continued cirrus streaming north. Temps will be on the increase with an increased southerly flow as well with highs reaching around 80 for east Kentucky. This will likely fall a few degrees short of the record of 83 for JKL and LOZ. Cloud cover will be on increase into tonight along with increased winds as the next front approaches from the west. This will lead to less fog development tonight and slightly warmer low temps. The increased cloud cover will lead to temps topping out around 80 again for highs on Sunday. Overall, a dry short term forecast will be on tap as precip should hold off from entering eastern Kentucky until Sunday night. Therefore, the forecast challenge lies with the impact to the highs and lows temperatures from the increased southerly flow. .LONG TERM...(Sunday night through Friday) Issued at 430 AM EDT SAT OCT 21 2017 Models are in good agreement through the bulk of the extended portion of the forecast, with more significant differences showing up in the latter 48 hours or so. The Canadian solution appears to be the outlier, with slightly better agreement between the ECMWF and GFS. While not great, the ECMWF has shown the best consistency through the last couple of runs. Overall the pattern is amplified and progressive. Digging, amplifying northern stream energy appears to lift a southern stream storm system up and through the Ohio Valley region early in the period. But significant differences in details remain with strength and timing of short wave energy tracking through the core flow of the eastern CONUS trough. Bottom line is that some phasing of these two systems will be possible which would influence the evolution and timing of events through the first half of the extended. Mid and upper level pattern then shifts rapidly during the last 72 hours of the period as the eastern CONUS trough lifts out to the northeast in response to energy carving out a deep trough across the western CONUS. The ECMWF is a bit more amplified and slower with the evolution of the pattern in general and digs the trough further west. The GFS advertises a much broader trough that encompasses just about the entire lower 48, which in turn brings storm systems further east more rapidly with time. For sensible weather a low pressure system will develop over the Gulf of Mexico and move rapidly northward, through the deep south and into the Commonwealth by Monday. This system will bring ample moisture and produce a soaking rain for our area. At present much of the area could see between an inch and an inch and a half of rainfall from Monday through Tuesday. A strong cold frontal system will sweep southward into the region late Monday night and through eastern Kentucky by early Tuesday morning. Immediately after a clipper like system will drop rapidly southeastward out of Canada and through the upper Ohio Valley by late Wednesday. Combined these three systems will usher in a breif shot of much colder air for our area during the mid week time frame. Temperatures will be low enough Thursday morning that frost will be a possibility, especially in our more sheltered valley locations. Thereafter temperatures moderate back up to normal levels through the remainder of the forecast window. && .AVIATION...
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(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 122 PM EDT SAT OCT 21 2017 The TAF sites should experience VFR conditions through out the period, with light winds and dry conditions also expected. The only cloud cover of note should be SCT to BKN high clouds that will persist during the period as well. Any fog that forms late tonight should be confined to valley floors and near bodies of water.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...SHALLENBERGER LONG TERM...RAY AVIATION...AR

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