Area Forecast Discussion
Issued by NWS Jackson, KY

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421 FXUS63 KJKL 152235 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 635 PM EDT Tue Aug 15 2017 .UPDATE... Issued at 634 PM EDT TUE AUG 15 2017 Forecast is well on track so far this evening. A few isolated showers are still ongoing across the southern portion of the CWA, but should begin to wind down as we lose daytime heating. Otherwise, the main update was just to freshen up the near term grids to make sure they are on track with current observations. All changes have been published and sent to NDFD/web. && .SHORT TERM...(This evening through Wednesday night) Issued at 308 PM EDT TUE AUG 15 2017 Models are in good agreement through the short term. Shortwave ridging aloft will transit the Ohio Valley region through the period. A shortwave trough will be approaching from the Plains at the end of the short term window. There are some weak embedded impulses in the flow as the ridge builds into the region late tonight and into Thursday. At the surface, a low pressure system will begin to take shape over the central Plains. In response, a warm front, quite subtle in nature, will lift northward through the area during the day Wednesday. Sensible weather will seem more like mid summer, with warm and muggy conditions expected through the period. Ongoing scattered to isolated convection will gradually dissipate through the late afternoon and early evening time frame with loss of diurnal heating. Weak subsidence aloft will help with radiative cooling potential through the overnight, though clouds will generally be on the increase with the approach of dawn and through the day Wednesday. With at least partial clearing and ample boundary layer moisture, fog would seem to be a good bet overnight. An almost indistinguishable surface feature, or subtle warm frontal boundary will lift northward Wednesday. Blends and model guidance ramp PoPs up through the afternoon in the warm sector as a result of diurnal heating and through the overnight period Wednesday into Thursday with the approach of the system to our west. .LONG TERM...(Thursday through Tuesday) Issued at 308 PM EDT TUE AUG 15 2017 A low pressure system will be crossing the Great Lakes at the beginning of the period with a warm front lifting to our northeast, placing eastern Kentucky in the warm sector with somewhat warm and muggy conditions in place on Thursday. This moisture and warmth will help to generate scattered showers and storms during the day. The cold front associated with the system in the great lakes will then cross the area Thursday night, producing additional chances for showers and storms. The front could be a slower mover with rain chance lingering ahead of the front into Friday afternoon. By Friday evening, most models have the front exiting to our southeast, providing a return of drier weather. As we head through Saturday, a shortwave trough will cross the Ohio river valley and could bring an isolated shower into eastern Kentucky late in the day, but instability and moisture is very limited by this point, so confidence is not high we will see much shower activity. Surface ridge will spread into the area from Sunday through Monday. While the ridge will help to suppress showers/storms, it may not be strong enough to prevent a few isolated showers popping each afternoon. The effects the eclipse will have on the shower chances on Monday is yet to be seen, but thoughts are we could see a 4 to 6 degree temperatures drop during the peak heating and if this occurs, we could see CU dissipate after the onset of the eclipse and limit overall rain chances. Lots of unknowns obviously, but have tossed a slight chance of a shower back into the forecast today. Either way, shouldn`t be a washout and any showers will be very isolated/short lived. Did account for a slight dip in temperatures in the afternoon, with a followup recovery following the eclipse. Temperatures from Thursday through Tuesday will remain mild with highs each day into the mid 80s and lows generally in the mid to upper 60s. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) ISSUED AT 150 PM EDT TUE AUG 15 2017 Scattered showers are refiring this afternoon, mainly south of Interstate 64. There is enough surface based instability to include the mention of thunderstorms for the first few hours of each TAF, exception being SYM which is north of the bulk of activity. With ample boundary layer moisture in place and at least partial clearing through the overnight due to some subsidence aloft, fog being advertised by model guidance seems reasonable. Made sure to include this in the forecast for each terminal. Winds will be light and variable through the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JMW SHORT TERM...RAY LONG TERM...KAS AVIATION...RAY

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