Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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394 FXUS63 KJKL 292103 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 503 PM EDT Mon Apr 29 2024 .KEY MESSAGES... - Showers and thunderstorms arrive from west to east tonight and linger into much of Tuesday. - Dry and trending warmer midweek, with near record highs on Thursday. - Unsettled weather returns for Friday and lingers through the weekend. && .SHORT TERM...(This evening through Tuesday night) Issued at 357 PM EDT MON APR 29 2024 We`ve been following this system moving in tonight for quite a while now. And with each forecast, it looks a little less and a little less impressive. A closed low is currently in place across Minnesota and will continue to shift northward into tonight, weakening only slightly. This will create a shortwave which should pass through the Ohio Valley tonight into Tuesday. At the surface, a low pressure system will be present moving across the Upper Great Lakes overnight. This system is already occluded and will continue to wrap around itself into the overnight. A cold front connected to this low will be orientated from NE to SW, slowly sweeping the Commonwealth tonight and during the day Thursday. Perhaps it`s because we are quite a distance away from the parent low, perhaps it`s because the cold front never quite makes it all the way through the state before lifting back northward, or perhaps it`s because there isn`t a large airmass shift with this system...either way, the warm moist environment in place and passing boundary would support the potential for thunderstorms, but they just don`t look very strong. There is very little organization (llvl wind sheer is basically nill), the sounding is very saturated, and there is very little CAPE. That being said, a more likely concern with these storms as they move in is the heavy rain potential. Can`t rule out that some locations could receive heavy downpours from storms that may lead to some isolated flooding concerns. The system should finally exit to our east by Tuesday evening. Light and somewhat variable surface winds are expected behind this system overnight, along with dry air advection, helping to clear out the skies. With this set up, expect cooler temperatures Tuesday night compared to tonight, and it is possible that some of the deeper valleys could decouple and drop temperatures fairly quickly. Tried to include a ridge/valley split in the forecast, though if it does pan out, may not have gone extreme enough on the differences. .LONG TERM...(Wednesday through Monday) Issued at 445 PM EDT MON APR 29 2024 As the long term period begins, a shortwave trough is expected to extend from VA to the Carolinas and then off the eastern seaboard with upper level riding extending north from the Gulf of Mexico into the Lower OH Valley region with a trough extending to the southwest Conus from an upper level low near the US/Canadian border. Another upper level low/trough is expected to be approaching the Pacific Northwest as it moves around ridging over the Pacific and into the trough. At the surface, a wavy frontal zone is expected to extend from south of Cape Cod to the mid Atlantic states to WV and then northwest as a warm front to sfc low pressure near the western sections of Lake Superior. A cold front should extend south and then southwest from this system into the Central Plains and then west into the western Conus. Sfc high pressure meanwhile should be centered over the TN Valley and Southern Appalachian region and extend into the Commonwealth as the period begins. From Wednesday to Thursday night, the pattern is expected to amplify at least briefly with upper ridging building into the Southeastern Conus to eastern Great Lakes region before the axis shifts east of the Appalachians on Thursday night and should extend from off the coast of the Carolinas to the mid Atlantic states to portions of eastern Ontario and into Quebec as the period begins. Meanwhile, as the axis of the upper ridge moves east, a shortwave should move from the Rockies to the Plains and then to the mid and upper MS Valley to OH and TN Valley regions by late Thursday night as the upper low meanders near the US/Canadian border from MT and the Dakotas and Saskatchewan and Alberta border areas. At the same time, the sfc low initially near Lake Superior is expected to track into Ontario and Quebec to the Maritimes with the boundary initially north and eastern of eastern KY lifting north as a warm front. Meanwhile a second sfc low should develop/organize to the lee of the Rockies in the CO/KS to OK panhandle region and then trek across the Central Plains to the Upper MS Valley/western Lake Superior region through Thursday night. At the same time, sfc high pressure will remain across the Southern Appalachians to Southeast Conus region and upper level ridging will usher in a warm and dry airmass. PW is forecast per 12Z LREF mean to drop to the 0.6 to 0.9 inch range for Wednesday to Thursday, before rising to 0.8 to 1 inch late Thursday night. Friday to Saturday night, the consensus of guidance is for the next shortwave trough in southwest flow should work across the Commonwealth on Friday to Friday evening while a cold front works east across the Commonwealth from Friday through Saturday as the associated sfc and upper lows track north across northwestern Ontario and then toward the Hudson and James Bay regions. The 500 mb trough axis should linger south into the Central Conus to MS Valley regions by late Saturday into Saturday night though this trough largely pass north of eastern KY to end the weekend as the flow aloft becomes more westerly. Additional disturbances should move from the Plains toward the OH and TN Valley region during that time while a secondary boundary is expected to have dropped south of the Great Lakes to end the weekend before stalling near or north of the OH River late in the period. PW should climb to 1.1 to 1.3 per the 12Z LREF mean to begin the weekend before decreasing to closer to 1 inch to end the weekend. A warming trend should follow locally as 850 mb temperatures should climb to the 13C to 15C range or so on Wednesday and then to the 16C to 18C range on Thursday. Near record highs will be possible on Thursday in the warm sector ahead of the next approaching system. The NBM deterministic was near or below the 25th percentile and hedged more toward the warmer 50th percentile. Some of the warmer valley locations will probably reach 90, especially in the Big Sandy region and into the KY basin. Dewpoints in the 50s on average will lead to min rh near or below 30 percent in some instances on Wednesday, while min rh should reach 25 percent or lower in several areas for Thursday. With moisture increasing late Thursday night into Friday and continuing into the weekend with series of passing disturbances along with the first front moving across eastern KY to begin the weekend while a second boundary sags toward the OH Valley to end the period, unsettled weather returns. Chance or higher pops were used from Friday afternoon to Monday. Chances for showers and some storms should generally peak each diurnal cycle though the boundary and upper disturbance passing Friday to Friday evening along the boundary slowly moving east focus chances later Friday night into Saturday afternoon. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) ISSUED AT 157 PM EDT MON APR 29 2024 VFR conditions are currently in place across the region, with increasing SW flow. Unfortunately the pattern is beginning to change, as a system is nearing from the west. Gusts should cease by this evening, but predominate SW flow should linger. Showers and scattered thunderstorms should begin to move in from the west to east overnight, with scattered to widespread precip expected to continue through the TAF period. Ceilings will slowly diminish throughout the period as well, eventually reaching MVFR status by late tomorrow morning and early afternoon. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JMW LONG TERM...JP AVIATION...JMW