Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 230521 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 121 AM EDT Thu Mar 23 2017 .UPDATE... Issued at 100 AM EDT THU MAR 23 2017 Surface analysis at this overnight hour shows surface high pressure is centered along and near Lake Erie. We remain under the influence of this surface high with light winds out of the NE, however, the deeper valley sites have been able to decouple. GOES 16 IR data does show some high clouds are streaming across, with the overall best coverage in the Lake Cumberland region. Therefore think the Freeze Warning remains reasonable this hour. Otherwise forecast is on track and therefore only minor changes are needed to deal with the latest obs. UPDATE Issued at 1000 PM EDT WED MAR 22 2017 Forecast looks on track tonight, so only update was to remove evening wording from the products. Otherwise, forecast is in good shape and no changes needed to ongoing freeze warning headlines. && .SHORT TERM...(This evening through Thursday night) Issued at 335 PM EDT WED MAR 22 2017 High pressure anchored across Lake Michigan will drift southeast this evening, allowing for a few cirrus clouds to gradually shift across south central Kentucky. Increasing relative humidity values will ensue as temperatures cool into the upper 30s across the Bluegrass region and 40s elsewhere early this evening, while northeast winds diminish to near or below 5 mph as the pressure gradient relaxes. Fire weather concerns will thus come to an end by dusk. With clear skies for a period this evening and tonight across the Big Sandy region of eastern into northeast Kentucky, temperatures will quickly fall through the 30s and into the 20s. A Freeze Warning will be in effect at 11 pm through 10 pm Thursday morning as temperatures below 30 degrees look to be a sure bet for a few hours, given dewpoints this afternoon in the teens and efficient radiational cooling. While low temperatures should fall into the upper 20s to low 30s for much of eastern Kentucky, valley locales, especially in far eastern into northeastern Kentucky, will likely fall into the low to mid 20s. Moisture will increase Thursday as surface ridging shifts across the Appalachians and upper ridging slides overhead aloft. Precipitation looks to remain northwest of the Bluegrass region later in the afternoon toward evening nearer a warm front lifting north ahead of a surface low ejecting out of the Front Range. Forecast soundings show subsidence being far too strong to support anything locally, despite deep layer moistening and precipitable water values approaching 0.75 to 1 inch. May still see RH values approach 25-30 percent across far eastern Kentucky before moisture advection takes place into the afternoon as winds veer southerly near 5-10 mph. Increasing heights/thicknesses underneath the approaching ridge will warm temperatures into the 60s. Warm air advection Thursday evening/night will continue, leading to a much warmer night in the low-mid 40s. .LONG TERM...(Friday through Wednesday) Issued at 335 PM EDT WED MAR 22 2017 The models are in fairly good agreement through the weekend, but then begin to diverge as we move into next week. Dry warm weather will be on tap for Friday with south to southwest flow ahead of an upper level low pressure system and associated surface low over the southern plains. This system will move northeast towards the Great Lakes over the weekend, bringing shower and thunderstorm chances to eastern KY. The trend has been to slow the arrival of shower chances for Saturday afternoon, and will continue with this idea. Much of Saturday looks to be dry, with shower chances becoming likely during the evening, with categorical probabilities overnight, along with a slight chance of thunderstorms. The high rain probabilities will persist into Sunday morning, with shower and thunderstorm chances decreasing from west to east during the day Sunday. With the track of the low to our west, temperatures will remain well above normal through the weekend. Behind the weekend system an upper level trough and associated surface low will emerge from the southern plains and again move northeast early next week. This will bring shower and possibly thunderstorm chances back to the area mainly late Monday, with shower chances lingering into at least Tuesday. However, there is not good agreement on the evolution of the upper air pattern for the early to middle part of next week. The 12Z GFS phases the southern stream system already noted above with a northern wave, with the result being pronounced troughing from the Great Lakes into the OH Valley. The 12Z ECMWF quickly moves the southern stream system through with no phasing and much less overall troughing. The result is that the GFS allows much cooler air to push into eastern KY by mid week, while the ECMWF keeps temperatures much more mild. In fact by 18Z Wednesday the GFS shows 850 mb temperatures anywhere from -2 to 3 C across the area, while the ECMWF has temperatures generally around 10 C. The standard model blend leans towards a solution that is warmer than the 12Z operational GFS and this makes sense considering the operational GFS is on the cool side of the GFS ensemble members, and several degrees cooler than the GFS ensemble mean. && .AVIATION...
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(For the 06Z TAFS through 06Z Thursday night) ISSUED AT 121 AM EDT THU MAR 23 2017 Surface high pressure will continue to influence the region through the TAF period leading to VFR conditions. Winds will remain light out of the northeast to begin the period and then veer to the south as we move through the day Thursday.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... Freeze Warning until 10 AM EDT this morning for KYZ044-050>052- 058>060-068-069-079-080-085>088-104-106>120. && $$ UPDATE...DJ SHORT TERM...GUSEMAN LONG TERM...SBH AVIATION...DJ

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