Area Forecast Discussion
Issued by NWS Jackson, KY

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890 FXUS63 KJKL 240537 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 137 AM EDT Sun Sep 24 2017 .UPDATE... Issued at 1018 PM EDT SAT SEP 23 2017 The forecast remains on track so far tonight. Ingested the latest obs data into the hourly forecast grids to establish new trends. The hazardous weather outlook was updated to remove afternoon wording. UPDATE Issued at 728 PM EDT SAT SEP 23 2017 The forecast is looking good so far this evening. Still expecting calm winds, mostly clear skies, and areas of valley fog overnight. && .SHORT TERM...(This evening through Sunday night) Issued at 350 PM EDT SAT SEP 23 2017 An upper level high pressure system across the Great Lakes into the Ohio Valley will keep above normal warmth in place through the weekend. An accompanying surface ridge and subsequent deep layer subsidence will keep the vast majority of eastern Kentucky dry, with the possible exception being a locale or two across far southeastern Kentucky. Areas on an eastward facing mountain slope will stand the best chance for a shower where orographic forcing will be enhanced as east/northeast winds prevail. A popup shower may also develop closer to the southern extent of the Lake Cumberland region on the northern periphery of some remnant energy from a low sitting in the Gulf of Mexico. Not expecting a great deal of rainfall from any showers that can develop locally, nor any lightning as convection will not be deep enough to generate electrical activity. Cloud cover, mainly confined south of Hal Rogers Parkway/Highway 80 nearer to what lift is present, will dissipate this evening leading to clear skies overnight. This will once again promote radiation fog in river valleys as winds remain light and dewpoints reside in the upper 50s to lower 60s. Valley temperatures look to cool into the upper 50s to near 60 with ridges remaining in the low 60s. A fairly similar pattern will materialize for Sunday with deep layer subsidence overhead. Will keep rain chances out of the forecast for now as the upper high nudges slightly south and east into the Appalachians, resulting in a minor uptick in upper height fields and similar afternoon temperatures in the mid 80s. .LONG TERM...(Monday through Saturday) Issued at 350 PM EDT SAT SEP 23 2017 The period begins with upper level high remaining in control of the eastern half of the CONUS along with general surface high pressure. The initial upper level high will be replaced by a southwest building ridge. This ridge is poised to breakdown, as an upper level trough swings into the upper Midwest by Friday. This will lead to lowering heights by the end of the week into the weekend, and much cooler temperatures with 850mb temperatures getting into the single digits. Overall models are in decent agreement with the pattern, however, some differences toward the end of next week could lead to differences in temperatures. Also some disagreement in how the front will play out on Wednesday into Thursday, but think the chances of showers remains low given the displacement from surface low and lack of cyclonic flow aloft. Sensible weather wise we are looking warm weather through Wednesday. A weak cold front will progress east by Wednesday night into Thursday, and perhaps some showers in the far SE Thursday afternoon. Most could be dry for quite sometime if the trends continue. Then the near to below normal temperatures will spread into the Ohio Valley to round of the long term period. && .AVIATION...
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(For the 06Z TAFS through 06Z Sunday night) ISSUED AT 137 AM EDT SUN SEP 24 2017 High pressure just to our NE will remain the driving factor through the TAF period. As has been the case for nights previous, conditions are favorable for fog development, especially in the valley locations. The setup will be very similar to last night, with onset of fog starting after 6Z, eventually dropping to LIFR or worse conditions in the valleys after 9Z and continuing through 12Z. At the TAF sites, a little bit more tricky as to if the fog will impact them. Based off of what occurred last night, tried to trend accordingly for timing, hedging towards slightly less impacts. Used tempo MVFR for JKL/SME/LOZ where it is possible fog may not impact TAF sites at all. However, given the impacts that occurred last night at SYM and SJS, trended towards predominate MVFR and TEMPO IFR conditions here. Will adjust as needed once fog begins setting up. Once fog dissipates this morning, expect mostly clear skies and VFR conditions to prevail for the remainder of the TAF period. Winds will be light and variable through the period.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...AR SHORT TERM...GUSEMAN LONG TERM...DJ AVIATION...JMW

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