Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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999 FXUS63 KJKL 302056 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 456 PM EDT Tue Apr 30 2024 .KEY MESSAGES... - Following recent rain, high pressure builds in leading to clearing and light winds setting the stage for dense fog potential tonight and Wednesday morning. - Dry and trending warmer Wednesday to Thursday, with near record highs on Thursday. - Unsettled weather returns for Friday and lingers through early next week. && .SHORT TERM...(This evening through Wednesday night) Issued at 440 PM EDT TUE APR 30 2024 A mid and upper level shortwave trough is moving across portions of the OH Valley and Appalachians at this time while riding extended north from the Gulf of Mexico into the Lower OH Valley region with broad troughing extending south across the western US from an upper level low near the Northwest Conus/Canadian border area. A weak cold front/surface trough is crossing the eastern KY region at this time. Showers are moving across the area in advance of these features with only very minimal in cloud activity briefly detected over the past hour or so. West of the area, a ridge if high pressure extends from the lower MS Valley to the Lower OH Valley region. Further west, an area of low pressure was tracking from portions of the Central Plains toward the Upper MS Valley. This evening and tonight, the upper level trough and weak surface boundary will move east of eastern KY this evening with the upper level ridge building in behind it. Meanwhile, a shortwave trough will move from the Plains to upper MS Valley and then across the Great Lakes through Wednesday and toward the St Lawrence Valley through Wednesday night. A general trend of height rises is anticipated from tonight through Wednesday across the Commonwealth. At the same time, the sfc ridge of high pressure will build into eastern KY and the Southern Appalachian region. The axis of the upper level ridge will shift east across the area on Wednesday night while sfc high pressure remain in place across the southern Appalachians. Further to the north and west, a shortwave trough is expected to move from the Central Plains toward the Upper MS Valley. Shower activity across the south and east will gradually decrease from west to east during the evening as the shortwave trough and sfc system pass. Sfc and upper level ridging will build in behind this for tonight and lead to a clearing trend and slackening winds. This will also occur following recent rainfall and set the stage for fog formation and perhaps a few areas of low stratus as well. There is uncertainty in the areal extent and intensity of the fog, but some dense fog has been included in the grids, especially for valley locations. The fog may affect the morning commute and this potential is highlighted in the HWO. Under high pressure, a drying and warming trend is anticipated into Wednesday with mixing leading to lower afternoon dewpoints in the east and south compared to today. The pattern will be favorable for a moderate ridge/valley split as valley should decouple by sunset on Wednesday evening and fall to near or even below the afternoon mixed dewpoints. Lows in the deeper valleys should be near the 50 degree mark with coalfield ridges near 60. .LONG TERM...(Thursday through Tuesday) Issued at 327 PM EDT TUE APR 30 2024 The period begins with good agreement in the deterministic and ensembles on the mid-level ridging the Southeast US and high pressure off toward the Atlantic Coast line. This will keep the weather quiet, with very dry low levels and capping inversion aloft. This could lead to some flat cumulus in the afternoon, but very warm afternoon high temperatures in the mid-80s to near 90 degrees. This could eclipse record high temperatures, with JKL 87 degrees set in 2012 and LOZ 88 degrees set in 1959. The ridging does push east as a mid-level wave rides toward the Ohio Valley Thursday night into Friday. This will aid in giving way to showers and thunderstorms Friday afternoon, as moisture surges northward and small amount of instability comes with it. This as multi-model ensembles show 40-50 percent chance of greater than 250 J/kg of CAPE. Overall guidance, including ensembles are in good agreement with best chance of rain (around 60-70 percent) Friday night into early Saturday. There seems to be a little uncertainty on Saturday in terms of timing, with first wave and next shortwave pushing into the Midwest, Saturday night into Sunday. The deterministic and ensemble data are disagreeing on the amplitude of this wave too and leads more uncertainty by late weekend into early next week. Particularly as there could be some shortwave ridging in between these features. Therefore, the PoPs drop back into the 40-50 percent range mainly in the afternoon hours Sunday into Tuesday. It will remain 10 to 15 degrees above normal through this time range. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) ISSUED AT 215 PM EDT TUE APR 30 2024 Some isolated to scattered showers were moving across the region as of issuance time with some IFR ceilings in the far southeast and MVFR or VFR elsewhere. For all sites during the first 3 to 5 hours of the period, there continues to be a non-zero chance of thunder, but the risk overall remains too low to mention. Ceilings should trend to MVFR and VFR and then VFR areawide during the first 3 hours of the period, though some MVFR ceilings and/or vis are anticipated within showers. Clearing is anticipated tonight with winds becoming calm as high pressure builds in, setting the stage for fog development. This should particularly affect the valleys, though it appears likely that it will affect most areas including all of the TAF sites for at least a few hours between 03Z and 14Z. Visibilities as low as IFR to LIFR if not below airport minimums will be possible. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JP LONG TERM...DJ AVIATION...JP