Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 240744 AFDJKL Area Forecast Discussion National Weather Service Jackson KY 344 AM EDT SUN JUL 24 2016 .SHORT TERM...
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(Today through Monday) Issued at 344 AM EDT SUN JUL 24 2016 A decaying mesoscale convective complex, currently traversing southwest Michigan into central Indiana, will bring increasing mid to high clouds to eastern Kentucky this morning. This should somewhat inhibit full insolation and subsequently negate the need for a heat advisory. Nonetheless, heat indices will approach and exceed the century mark once again this afternoon for several locales. Will be close to record territory at Jackson, but currently thinking cloud cover may be just enough to keep the record high temperature of 93 degrees for the date untouched. Regarding precipitation, southeastward propagating outflow boundary ahead of said complex of storms may end up being the primary forcing mechanism for afternoon convection given a lack of any local upper features. The presence of a lingering and rather diffuse outflow boundary from prior day activity may also end up sparking a storm or two, but main lift will reside along newly generated boundary along with orographic forcing along the higher terrain from the Cumberland Plateau into southeast Kentucky near the Virginia state line. Showers and storms should wane this evening with the loss of daytime heating. An upper trough swinging through Ontario and Hudson Bay through the Great Lakes will then push a frontal boundary toward the Ohio Valley into early Monday, providing a larger forcing mechanism to focus upon for showers and thunderstorms. Moisture pooling along the front should send precipitable water values up toward the 1.9 to 2 inch mark, leading to a threat of heavy rainfall by late Monday afternoon as diurnal heating boosts instability and storm chances. Additionally, the right entrance region of an associated upper jet will skirt the Ohio Valley, thus further supporting rising motion. Gusty winds will also be possible with any storm given precipitation loading atop shallow drier air beneath cloud bases. .LONG TERM...(Monday night through Saturday) Issued at 344 AM EDT SUN JUL 24 2016 Models continue to be in good agreement from Monday night through midweek, with upper level ridging across the southern half of the conus, becoming increasingly dampened by shortwaves and troughs that pass across the northern half of the conus. This will keep much of the central conus, including the Ohio River Valley in a zonal flow pattern to start the period, becoming increasingly amplified as a deeper trough start pushing southward into the region for the second half of the work week. This deeper troughing pattern will lower heights across the Ohio River Valley starting Thursday. Then as shortwaves interact with this trough, expect it to continue deepening as we head into the weekend. Models continue to show very good continuity through the entirety of the period with these features. The first shortwave to impact the region Monday will bring with it a surface frontal boundary, which should push into the state Monday night, before becoming quasi-stationary during the day Tuesday. This will be the epicenter for convective development Monday night through Wednesday, with scattered to numerous showers and thunderstorms through this time frame. Best chances/coverage will be during the afternoon/early evening with the aid of peak heating. Instability and lift with these storms will be more than enough to produce strong thunderstorms, but there will be little in the way of steering flow, especially with the elongated stationary boundary across the region. As such, will likely see pulse-natured storms, but will need to be on the look out for both slow moving and training storms, which could lead to localized high rainfall amounts and potential urban or flash flooding. The frontal boundary will push north of the state Wednesday night, before deeper troughing and the next shortwave will near the region from the northwest. This shortwave will produce a surface low pressure center, which will interact with the surface boundary and increase its strength. However, as of the latest WPC frontal analysis, the boundary should remain north of the state through the remainder of the forecast period, slowly pushing in a more easterly direction. That being said, additional weak upper level disturbances will continue to drop into the region from the northwest, deepening the magnitude of the trough through the weekend. These disturbances, in addition to continued WAA and moist unstable air south of the boundary, will continue to spawn showers and thunderstorms throughout the period, with coverage and storm strength once again peaking in the afternoon. Winds may increase aloft somewhat during this time, but are forecast to remain fairly weak in the mid levels, so concerns for slow moving heavy rain producing cells will continue. The loss of mid and upper level ridging combined with daily convection will help keep our high temperatures close to normal for this time of the year, generally in the mid 80s. But with dew points hovering around the 70 degree mark, our weather will remain quite muggy. Likewise overnight lows will be warm, running a little above normals in the upper 60s to near 70.
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&& .AVIATION...(For the 06Z TAFS through 06Z Sunday night) ISSUED AT 203 AM EDT SUN JUL 24 2016 Current VFR conditions expected to mainly dominate through the period, with the best chance of sub-VFR conditions likely residing at SME nearer a local water source. May very well see similar conditions this morning around 10-12Z at JKL as valley fog mixes up the ridge. Any patchy fog will mix out by early-mid morning with a few cumulus developing by late morning into the afternoon as an overall slightly drier and more stable airmass takes hold today. Will have to monitor approaching mesoscale convective system across northern Indiana with plenty of moisture/elevated instability available downstream. Not expecting high enough coverage to include mention of thunder at any site. Winds will remain light through the period, generally averaging less than 5 knots from the south/southeast early to southwest this afternoon. && .JKL Watches/Warnings/Advisories... None. && $$ SHORT TERM...GUSEMAN LONG TERM...JMW AVIATION...GUSEMAN

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