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Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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195 FXUS63 KJKL 200015 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 815 PM EDT Fri Jul 19 2024 .KEY MESSAGES... - Showers and thunderstorms will impact the region at times through the middle of next week. There will be a minimum in rain chances into this evening, before higher probabilities set in over the weekend and continue into the new week. - Continued relief from the hot temperatures of earlier in the month will be with us throughout the period, though humidity makes a comeback heading into next week. && .UPDATE... Issued at 815 PM EDT FRI JUL 19 2024 Blended obs into the forecast without out any substantive changes. && .SHORT TERM...(This evening through Saturday night) Issued at 350 PM EDT FRI JUL 19 2024 19Z sfc analysis shows high pressure from the north having had the biggest influence on our weather today with slightly cooler than normal conditions, at least partial sunshine, and drier air in place. However, a stalled frontal boundary is lingering just to our south and this remains a source for potential showers and thunderstorms along our southeast borders this evening. It is also responsible for more clouds working in from the south with time into the night. Currently, temperatures are running in the low to mid 80s most places while dewpoints are generally in the upper 50s to lower 60s, amid light and variable winds. The models, and their individual ensemble suites, are still in near excellent agreement aloft through the the short term portion of the forecast. They all depict general troughiness through the Great Lakes and Ohio Valley with a tendency for a local minimum in heights to consolidate to the west over the Middle Mississippi Valley with time. This will collect much of the mid level energy in the pattern through the weekend with a few weaker elements drifting over eastern Kentucky during the short term portion of the forecast in broad, weak 5h flow. Given the small model spread, again have gone with the NBM as the starting point for the forecast grids with little adjustment needed aside from some incorporation of the latest CAMs guidance for PoPs this evening through Saturday night. Sensible weather features a moderation of our less humid and somewhat cool end to the work week with moisture on the increase along with milder nights on tap. This also means an increasing, but only gradually into Saturday morning, threat for showers and thunderstorms working up from the south as the front lifts back north and becomes more active. Still see a window consisting of much of the night for the northwest half of the area to have thin enough clouds to allow for some radiational cooling and limited terrain distinctions along with valley fog formation. For Saturday night, expect more uniform temperatures amid deep layer cloud cover and higher baseline dewpoints. Some places will see cooler conditions on Saturday but that is mainly due to more clouds in place and the convection around, otherwise near normal temperatures are anticipated. The main changes to the NBM starting point consisted of adding in some PoPs details from the CAMs for this evening through Saturday night. Did also tweak northwest parts of area for some minor terrain distinctions in temperatures through the night. .LONG TERM...(Sunday through Friday) Issued at 407 PM EDT FRI JUL 19 2024 There is good run to run continuity, thus not much change in the forecast. Better than usual agreement among the operational models. There is more divergence in the solutions by the end of the period, making it slightly less certain. Pattern aloft is amplified, but with a slow progression of systems. A mean trough sits over the Upper Midwest at the start of the extended and basically remains in place until the end of the entire period when a stronger, more progressive trough drops into the Great Lakes Region and effectively begins to kick the mean trough further east into the heart of the Ohio Valley. This mean trough does extend generally south-southwest into the souther Plains. A series of disturbances of varying strength track around the base of this mean trough before lifting northeast across the southeastern CONUS...and portions of the Commonwealth. At the surface, a nearly stationary, but wavy frontal zone will provide a focus for convection through the period. Sensible weather features a stormy extended as a series of disturbances track through the region. Based on model solutions and guidance, there will likely be a diurnal flavor to convection through the period. The additional cloud cover and rainfall associated with each passing round of convection will tend to keep daytime temperatures down, slightly below our normal mid 80s. Overnight lows will tend to remain up due to lingering cloud cover and moisture. Thus diurnal ranges will tend to be reduced through the period and made minor adjustments to the NBM initialization (highs and lows) to reflect this potential. With expected repetitive rounds of rainfall, can not rule out the possibility of locally heavy rainfall through the period. PWATS for this type of pattern are relatively low, generally running below 2 inches through the period. PWATS have trended slightly higher for Tuesday night and Wednesday, where they approach 2 inches. Freezing levels are not as impressive as they could be, generally around 13 kft or lower. Storm motion is between 10-15 kts from Sunday through Tuesday, then increase to between 15 and 30 kts for the remainder of the period. Thus in general, storm motion is not favorable for hydro issues unless some type of training sets up over some portion of the area. Overall probabilities for widespread flooding problems appear low based on ensemble probabilistic data. Ensemble probabilistic data is quite similar to yesterday at this time, showing a high probability of reaching an inch or more of total rainfall throughout the entire forecast period (Sunday through Friday) are basically around 80 percent or higher for the entire area. The probability of a total rainfall reaching two inches is greatest along and/or south of the Hal Rogers/Highway 80 corridor, between 60 and 80 percent. Thus average rainfall totals for the extended period could be as high as 1-2 inches in total, with a greater chance of reaching the 2 inches being across our southern most zones. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) ISSUED AT 815 PM EDT FRI JUL 19 2024 Valley fog will affect some locations late tonight and early Saturday morning, mainly in southeast KY, and possibly bringing IFR or worse conditions. Showers and thunderstorms are expected to affect some locations with sub-VFR conditions on Saturday, but confidence in timing/locations is too low to warrant anything more then VCSH and VCTS in TAFs. Outside of fog and precip, VFR conditions are expected during the period. Winds will be less than 10 kts. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...GREIF LONG TERM...RAY AVIATION...HAL