Area Forecast Discussion
Issued by NWS Jackson, KY

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000 FXUS63 KJKL 181802 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 202 PM EDT Mon Mar 18 2024 .KEY MESSAGES... - A deep trough passing aloft brings a threat of light snow showers and flurries this afternoon. - 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. - A passing dry cold front brings another day of Fire Weather concerns on Wednesday. - 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. && .UPDATE...
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Issued at 150 PM EDT MON MAR 18 2024 Forecast still in good shape, other than the clouds continuing to spread across the state faster than originally anticipated. Updated the grids to account for this. Will also confirm if any sprinkles are hitting the ground in our far northern counties, in case the weather grids need to be increased for an hour or so. Other tweaks, including temperature and winds, were made based on the ongoing conditions and resulted in only very minor changes. All updates have been published and sent to NDFD/web. The new forecast package was also sent out to remove morning wording. UPDATE Issued at 1103 AM EDT MON MAR 18 2024 |Forecast still seems on track so far through the morning. The only real change was to increase the cloud cover across our northern counties, speeding up it`s onset over the next few hours. ILN`s radar does show some low returns across Fleming and Rowan County. That being said, their radar beam is quite high in these locations, and despite the cloud cover, it is still very dry at the low levels. Called the EM in Fleming County and confirmed the cloud cover but nothing (flurries or sprinkles) were occurring. Therefore did not update the pops or weather grids at this time, only the cloud cover. All updates have been published and sent to NDFD/web. Went to update the zones/SAF, but it wanted to use late morning wording, which will then require another update at noon to remove the morning wording. Since the updates were very minor, going to wait until noon to send out the zone updates. UPDATE Issued at 730 AM EDT MON MAR 18 2024 Current forecast remains on track so have just added in the latest obs and trends for the T/Td/Sky grids. These minor adjustments have been sent to the NDFD and web servers.
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&& .SHORT TERM...(Today through Tuesday) Issued at 450 AM EDT MON MAR 18 2024 08Z sfc analysis shows high pressure attempting to build into eastern Kentucky from the west. However, a passing trough aloft will help to maintain cyclonic sfc flow over the area into the evening. This flow is responsible for the chilly temperatures this morning on northwest winds of 10 mph or less. Accordingly, readings are running in the low to mid 30s most places with a few sheltered spots able to cool into the upper 20s. Meanwhile, dewpoints are lower than temperatures, generally in the upper teens to lower 20s under a smattering of mainly high clouds. The models, and their individual ensemble suites, continue to be in pretty good agreement aloft through the short term portion of the forecast. They all depict a deep trough tilting through the southern Ohio Valley and across the Tennessee Valley today. This brings strong height falls, steep lapse rates, and a cluster of mid level energy through our moisture starved area this afternoon. This trough bottoms out to our south this evening and slips quickly east of the Appalachians leaving lower heights and northwest flow at 5h behind. The now very small model spread supports using the NBM as the starting point for the forecast grids with most adjustments related to terrain distinctions in temperatures tonight as well as extra mix down drying on Tuesday afternoon. Sensible weather will feature a cold day after our warmth of late with a northwest breeze adding to the chill. Dry conditions in the boundary layer should keep any light pcpn in the form of flurries and sprinkles, though an influx of moisture from the Great Lakes may be enough for a stray shower of light rain or snow (10 percent threat or less) - but more probable northeast of the JKL CWA. The clouds and light pcpn associated with the passing trough aloft will move off to the east tonight. These conditions, when combined with diminishing winds, will allow for better for better radiational cooling and a ridge to valley temperature difference to set up overnight and into Tuesday morning - enhancing the widespread hard freeze in the valleys especially. The recent warmth has encouraged many buds and blossoms to develop on the vegetation throughout the area and these are seriously threatened by tonight`s cold. For this reason (as the growing season has not been declared started, yet) an SPS has been issued giving heads up to those with agricultural and fruit tree interests. For Wednesday, the dry conditions combined with rebounding temperatures on breezy southwest winds will lead to humidity values well below 25 percent, for most. Combined with the winds pushing 15 mph sustained, at times, from mid morning into the afternoon there will be heightened fire weather concerns and a Red Flag Warning may be needed for at least portions of the forecast area for the latter part of the day. This concern will be addressed in the narrative portion of the forthcoming Fire Weather Forecast product. The main adjustments to the NBM starting point were to include more terrain distinction for temperatures tonight and also favor the 10 percent or lower version of the NBM for dewpoints on Tuesday afternoon. .LONG TERM...(Tuesday night through Sunday) Issued at 533 AM EDT MON MAR 18 2024 An amplified long wave pattern will be in place next week. Broader cyclonic flow will be fanned out from the Upper Midwest through the Great Lakes/Ohio Valley and through most of the Eastern Seaboard mid-week. At the surface, low pressure will move from southern Ontario through southern Quebec, with a progressive cold front to move southeast through the Ohio Valley, maintaining another dry and gusty day across eastern Kentucky for Wednesday, lending to ongoing fire weather concerns. Consequently, have used the 10th percentile of the blended guidance for dew points during peak mixing. Meanwhile, a southern stream low eases east, transitioning to an open wave by the time it reaches the southern Plains. The southern stream short wave will continue its eastward trek, passing through the lower Mississippi Valley by Thursday night, with surface low pressure and an associated inverted trough allowing for overrunning moisture to spread northward from the Tennessee Valley. Further north, an intense closed low will drop southeast out of Nunavut, riding the western shoreline of Hudson Bay. This will allow deeper short wave energy to move in from south central Canada, swinging through the Great Lakes and portions of the Ohio Valley on Friday, and then through New England by early this weekend. There is still some disagreement on how much northern stream influence there will be from this short wave, with the GFS somewhat deeper than the ECMWF. Still, models have come into somewhat better agreement with the aforementioned southern stream system, still justifying PoPs peaking on Friday at around 50%. Drier weather then returns for the majority of the weekend, as high pressure passes by to our north. Temperatures will cool off to below normal through Thursday, before moderating to near normal through the start of the weekend, and then rounding out the week above normal. && .AVIATION...
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(For the 18Z TAFS through 18Z Tuesday afternoon) ISSUED AT 201 PM EDT MON MAR 18 2024 A deep upper level disturbance is currently passing through the Ohio Valley. While high pressure and generally low RH is present at the surface, the upper level disturbance is resulting in a mid-level cloud deck which has overspread much of the TAF sites and will remain through much of the afternoon. While no measureable precip is expected from this system, especially given the dry low levels, can`t rule out a sprinkle or flurry making it to the surface this afternoon. This should have no impact on the VIS. Winds are predominately out of the NW between 5 and 15 kts, with gusts between 15 and 20 kts this afternoon thanks to deep mixing in place. Skies will finally clear heading into the overnight, as the upper level system exits east of region. Winds will also slowly dissipate throughout the overnight, but should remain fairly mixed at the TAF sites, so kept predominate wind conditions. High pressure will be the main weather driver overnight and during the day Tuesday, with VFR conditions on tap. Predominate winds will be more SWrly and breezy during the day Tuesday as mixing increases again, but otherwise expect clear and dry conditions to finish out the forecast period.
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&& .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JMW SHORT TERM...GREIF LONG TERM...GEOGERIAN AVIATION...JMW

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