Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 180555 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 155 AM EDT Mon Mar 18 2024 .KEY MESSAGES...
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- A deep trough passing aloft brings a threat of light snow showers and flurries on Monday afternoon. - Freezing conditions into dawn this morning and a hard freeze later tonight could kill any cold sensitive vegetation that has emerged prematurely due to early season warmth. - Gusty southwest winds transport warmer air into the region on Tuesday, but dewpoints are slower to rise leading to low afternoon relative humidity and Fire Weather concerns. - Temperatures rebound back to near normal for Wed and into next weekend, with lower confidence in the next potential chance of precipitation moving in towards the end of the work week.
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&& .UPDATE...
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Issued at 140 AM EDT MON MAR 18 2024 The current forecast is right on track early this morning as the winds are starting to go light allowing for better radiational cooling the rest of the night. Have mainly just added in the latest obs and trends into the T/Td/Sky grids. These minor adjustments have been sent to the NDFD and web servers. UPDATE Issued at 1126 PM EDT SUN MAR 17 2024 The forecast remains on track. A surface trough axis has worked southeast of the area, with an uptick in wind gusts in the 20 to 25 kt range noted at some of the observation sites. These winds will be diminishing through the overnight, as the better pressure gradient pushes closer to the Appalachians with time. Forecast lows in the upper 20s to lower 30s still look on track. Mainly updated the hourly temperatures and dew points once again through the overnight. Updates have been sent. UPDATE Issued at 806 PM EDT SUN MAR 17 2024 Thicker high clouds will exit off to our east early this evening, with some higher-based cumulus also generally drying up to our north with sunset. Gustier west winds will also gradually diminish through the evening, hanging on the longest on ridgetops and more open areas north. The forecast remains on track early this evening, and have only freshened up the sky cover through midnight, as well as adjusted some of the hourly temperatures to better match the trend in the observations.
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&& .SHORT TERM...(This evening through Monday night) Issued at 357 PM EDT SUN MAR 17 2024 As of mid afternoon, an upper level low was centered near the Ontario and Quebec border with an associated upper level trough extending into the Great Lakes, Upper and mid MS Valley regions, and much of the eastern Conus. Further west, an upper level ridge extended from the eastern Pacific into the Northwest, portions of western Canada, and into portions of the Northern Rockies. A closed low was centered southwest of the Four Corners region in AZ with a series of weaker shortwaves in west to southwest flow from Mexico across the Southern Plains to the Gulf Coast states. At the sfc, an area of low pressure associated with the upper level low near the Ontario and Quebec border with a triple point low over northern ME and a trailing cold front near the eastern seaboard to the Delmarva and then southwest to northern portions of the Gulf Coast states to TX. Another boundary was further south from east of the coast of the Carolinas across the Gulf Coast region to the lower portions of the Rio Grande valley and then into Mexico. Meanwhile, a ridge of sfc high pressure was centered near the Saskatchewan and Manitoba border and extended through the Northern to Central Plains and also extends east into the Lower OH Valley. This evening through Monday, the upper level low is progged to track east and northeast toward the Maritimes while the axis of the 500 mb trough is expected to rotate across the St Lawrence valley and Great Lakes to the Northeast Conus to Mid Atlantic states and portions of the OH Valley and to the southern Appalachians through sunset on Monday evening. The axis of this trough will shift east of the area to end the period while mid level height rises occur across the OH Valley including the Commonwealth. At the same time, the sfc ridge of high pressure is expected to build south across the Plains and into the Lower OH Valley and TN Valley as well as the Lower MS Valley to end the period. As the 500 mb trough axis/shortwave approaches on Monday and Monday evening, moisture is expected to increase generally in the 850 mb to 700 mb layer. At the same time, cold air advection that is ongoing at present will have continued through tonight and through the day on Monday as well. Daytime heating combined with the gradual cooling aloft will lead to development of rather high based cumulus and stratocumulus. Saturation to the DGZ is anticipated with much of the cloud depth potentially residing within it Monday afternoon to early Monday evening. A dry subcloud layer and dry adiabatic lapse rates should support what precipitation that falls from the rather high based cumulus either sublimating or reaching the ground as snow flurries despite temperatures that may be near 40 or in the lower 40s in locations below 2500 feet elevation. Overall, based on the trends in coverage from the 12Z HRRR and 12Z Namnest, the coverage of potential for flurries was expanded to include most of the area on Monday afternoon, especially from near Interstate 75 and points east. The main forecast concern of the period is anticipated scattering of clouds and clearing as winds slacken on Monday night. This should lead to lows well down into the 20s, which ordinarily is not impactful. However, recent mild weather has led to some vegetation prematurely emerging and any such vegetation will be susceptible to the below freezing temperatures. Although the official start of the growing season has yet to begin, in consideration of this this threat has been added to the HWO. Some locations will also experience sub freezing temperatures for the upcoming night as well. With the cold airmass and 850 mb temperatures falling from the -5C to around -10C range to about -7C to -9C on Monday evening, highs Monday will be below normal and more typical of mid January highs. Normal highs for this time of year are in the mid to upper 50s. .LONG TERM...(Tuesday through Sunday) Issued at 332 PM EDT SUN MAR 17 2024 The primary forecast concerns in the extended will be the potential for low dewpoints and very dry conditions across the area on Tuesday and generally above normal temperatures. With winds still expected to be blustery and perhaps a bit gusty to begin the period, there could be some fire weather concerns for eastern Kentucky. This threat has been highlighted in the HWO. A ridge of high pressure will be the dominant weather system to start, but a weak area of low pressure passing by to our south, will bring rain chances back into the picture late in the week and into the upcoming weekend. The overall large scale upper level pattern to begin the period will feature a trough of low pressure moving slowly into and across the Desert Southwest and across the southern CONUS over time. This will be the system that brings rain to our area toward the end of the period. High pressure will dominate the weather of the southeastern CONUS initially, but another expansive trough of low pressure is forecast to dive southward out of Canada Wednesday and Wednesday night. Since it appears this system will be moisture starved, we should see nothing more than scattered clouds across the area as this system moves through aloft to our north and northeast. The southern stream trough mentioned earlier, will be our next weather maker Thursday night through Sunday. Another weak northern stream system might also be moving through during this time, and could influence our weather as well, but the southern stream low still looks like the main show. && .AVIATION...
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(For the 06Z TAFS through 06Z Monday night) ISSUED AT 155 AM EDT MON MAR 18 2024 VFR conditions will prevail through the period with just a smattering of high clouds into daybreak. A passing deep upper level disturbance will move through the region during the day. This brings scattered to broken clouds ranging from 4-6k feet agl, with perhaps a fleeting sprinkle or flurry. Winds will continue to be the main aviation concern at the terminals, though. They will be light into dawn then pick up from the northwest increasing to around 10 kts, with gusts of 15 to 20 kts by mid to late morning, as deeper mixing commences across the area.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...JP LONG TERM...AR AVIATION...GEOGERIAN/GREIF

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