Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 262357 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 757 PM EDT Mon Sep 26 2016 .UPDATE...
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Issued at 757 PM EDT MON SEP 26 2016 Outside of a rogue sprinkle in the higher terrain, rainfall has come to an end across eastern Kentucky. Drier air will continue to filter east behind the cold front, now positioned on roughly a Pittsburgh to Charleston to Bristol line. Cloud cover will decrease and lift through the evening into tonight, setting the stage for at least some patchy fog development in river valleys. Areas that saw rain Monday afternoon, mainly across the Bluegrass region and along the Virginia/West Virginia borders, will also stand a decent shot at seeing some lowering visibilities by Tuesday morning. Timing of the impending clearing and strength of the dry air advection will have to be monitored in regard to how widespread/dense any fog will become.
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&& .SHORT TERM...(This evening through Tuesday night) Issued at 327 PM EDT MON SEP 26 2016 A cold front is currently moving across eastern KY as of 3pm today. While the initial line of showers and thunderstorms has sheared out along the weakening frontal boundary during its eastward progression, warm air and clear initial conditions across far eastern KY helped to increase instability across this area during the early afternoon. A gust front which pushed out well ahead of the initial line then became the spawning ground for another line of showers and thunderstorms across far eastern KY. For the rest of the afternoon, expect the showers along the frontal zone to continue to shear out and breakup. Meanwhile the secondary and more robust line of showers and thunderstorms will continue to slowly move east of the state. Also cannot rule out some isolated to scattered convection between the two lines for the next few hours as well. Since NW flow began ahead of the actual cold front, and cloud cover is in place, expect cooler temperatures to continue to penetrate the CWA through the rest of the afternoon. This will only work to weaken any convection potential. The 850 mb frontal passage will traverse the CWA later this evening and into the overnight, generally after 0z. It is at this point that we will really start to tap into the much cooler airmass to our NE. Strong NW to SE upper level flow will feed Canadian air into the region throughout the remainder of the short term thanks to a strong upper level closed low circulating to our north. Low temperatures tonight will fall into the upper 40s to low 50s once we begin clearing out behind the frontal passage. Temperatures tomorrow will finally feel more seasonable, if not a couple degrees below, topping out in the low to mid 70s with surface high pressure in control. Clear conditions will continue Tuesday night with temps expected to fall back into the 40s with light southerly winds. .LONG TERM...(Wednesday through Monday) Issued at 302 PM EDT MON SEP 26 2016 Models continue to come into better agreement concerning a large upper low to affect the eastern CONUS early in the period. The ECMWF has been the most consistent in handling the system over the last few days. A model blend will be used to account for remaining differences. The upper low will be slowly dropping south from the Great Lakes on Wednesday, and should bottom out over KY on Thursday. Even with a cool surface air mass in place, cold air aloft should result in lapse rates steep enough for showers and possibly even some thunderstorms to occur. Precip timing and location will depend partly on small scale features rotating around the large system, with timing also being linked with diurnal destabilization. Model handling of small scale features will go through changes yet, which puts a limit on forecast confidence. Will not use any pops above chance category at this point, but that could change in later forecasts. Diurnal trends are more predictable and will be incorporated. The low should lift back north over the weekend, taking precip with it. Low level warm air advection is expected to be slow to return, but additional sunshine and mixing, and warming temps aloft will allow for a slow warming trend. && .AVIATION...
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(For the 00Z TAFS through 00Z Tuesday evening) ISSUED AT 757 PM EDT MON SEP 26 2016 MVFR ceilings will lift to VFR levels this evening and early tonight as dry air filters into eastern Kentucky in wake of a cold front pushing into the Virginias. Light northwest winds of 5 knots or less will ensue as cloud cover decreases and lifts through the night. Given this clearing, valley fog will be a decent bet, especially where rain fell this afternoon nearer the Bluegrass region and along the Virginia/West Virginia borders. Have inserted some MVFR fog at SME, due to earlier clearing tonight, and SYM where very light rain fell Monday afternoon. LOZ/JKL/SJS all remained dry today and will see a little later clearing, especially for JKL/SJS. Have therefore kept VFR visibilities in play through the night for now, but will have to closely monitor how quickly clearing progresses. Other limiting factor to fog development may be the dry air advecting in behind the front, but would nonetheless expect some development in river valleys as temperatures quickly cool overnight.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GUSEMAN SHORT TERM...JMW LONG TERM...HAL AVIATION...GUSEMAN is the U.S. government's official web portal to all federal, state and local government web resources and services.