Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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804 FXUS63 KJKL 290050 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 850 PM EDT Fri Jun 28 2024 .KEY MESSAGES... - Hot and humid weather is expected Saturday, with afternoon highs around 90 degrees and heat indices peaking around 100 degrees in some places. - There is potential for thunderstorms area-wide Saturday into Sunday as a cold front approaches and moves through. A few storms on Saturday afternoon and evening could produce strong wind gusts, large hail, and heavy rain. - Another short-lived break from the heat and humidity is expected on Monday behind the cold front, quickly followed by a return of sultry conditions. - An active period of showers and thunderstorms may impact the Fourth of July holiday period from Wednesday through Friday of next week. Best chances for showers and thunderstorms as of now are expected Thursday July 4th during the afternoon and evening. Heat indices will return to near 100 degrees for some locations as well during this time period. && .UPDATE... Issued at 850 PM EDT FRI JUN 28 2024 00Z sfc analysis shows high pressure off to the east of Kentucky as low pressure and a cold front is approaching the area from the west. Between these systems, southerly winds of 5 to 10 mph have brought in very warm and moist air. As a result, temperatures topped out in in the upper 80s and lower 90s most places with heat indices approaching 100 degrees in many locations. Currently, readings have started to fall back into a range from the upper 70s to middle 80s. Meanwhile, dewpoints have risen into the upper 60s and lower 70s. Still a stray shower or two are located in the far east but that should be the last of them tonight as they fade out over the next hour. Have updated the forecast mainly to fine tune the limited PoPs through the night and also to tweak the river valley fog into dawn Saturday. These minor adjustments have been sent to the NDFD and web servers along with the forthcoming freshening of the zones, HWO, and SAFS. && .SHORT TERM...(This evening through Saturday night) Issued at 320 PM EDT FRI JUN 28 2024 Eastern Kentucky will reside between a west-east ridge gradually strengthening with time across the Deep South, and fast westerly flow moving across the Upper Midwest and Great Lakes into the northern Mid-Atlantic region. Upper-level heights will be building with time into Saturday evening, then begin to fall a bit more abruptly Saturday night as an upper disturbance moves toward the region. Warm and moist air continues to advect north into the region with low-level flow becoming more southerly, with dew points generally rising about 10 degrees over the last 6 hours ending at 2 PM this afternoon. With the moisture advection there has been scattered to broken cumulus development across the area, but this activity is struggling to punch through a warmer, stable pocket of air aloft. Overnight models last night suggested some weakening of the cap late this afternoon through mid-evening, especially as low-level winds increase toward dark, but 12z models somewhat backed off of this idea. Nevertheless, while the afternoon package backs off PoPs somewhat there is an the possibility of an isolated shower or thunderstorm late this afternoon into the evening. The bigger story tonight will be poor temperature recovery as lows are likely to remain well into the 70s as warm advection strengthens. The European model Extreme Forecast Index (EFI) depicts lows on the high-end of the climatological range. Have also adjusted Sky cover upwards toward the CONShort model rather than the NBM given the warm moist advection into the region. Even the typically cooler sheltered valleys are likely to remain on the upper end of climatology, with only a few locations likely to drop into the 60s. Shower and thunderstorms increase through the day Saturday as an upper disturbance moves east across the Ohio Valley through the afternoon. Drier mid-level air will likely get advected over the humid lower atmosphere, which should allow convection to initiate despite subtle upper-level height rises. The NBM suggests high-end chance to likely PoPs (50 to 60) for the afternoon and these seem reasonable extending into the evening and overnight with some reduction in PoPs to 30 to 40 percent in the western and northwestern parts of the forecast area after midnight. With dew points remaining well into the 70s ahead of a cold front, expect another night of warm temperatures and high humidity. Increasing winds aloft associated with the passing disturbances aloft Saturday into Saturday night will provide sufficient shear to support a marginal severe weather risk, with damaging winds the primary threat and large hail a lesser threat. The greatest severe risk is toward Interstate 64 and points north, though severe weather can not be completely ruled out anywhere. Additionally, with PWs on the upper end of climatology, torrential downpours with storms will be possible. Any training of storms would increase the likelihood of flash flooding, with this threat also falling into the category of Marginal by the Weather Prediction Center. Lastly, the combination of oppressive humidity and high temperatures near 90 degrees Saturday will mean heat indices approaching or perhaps slightly exceeding 100 degrees during the afternoon. Note that while the criteria for a Heat Advisory is fairly widespread coverage of heat indices at or above 105 degrees, the heat will still have impacts on more vulnerable populations, such as young children, the elderly, livestock, and pets. .LONG TERM...(Sunday through Friday) Issued at 330 PM EDT FRI JUN 28 2024 The period starts Sunday morning with a cold front passing through the CWA. This will keep likely pops across the eastern CWA, increasing in magnitude a bit during the afternoon with peak heating. The front will finally shift off to the east Sunday evening, bringing a quick end to any ongoing precip. While temps on Sunday are forecast to be in the upper 80s, post frontal temperatures on Monday will be between 5 and 10 degrees cooler, with highs in the upper 70s and low 80s. A strong area of high pressure will take hold during the day Monday for much of the Ohio Valley and Great Lakes regions. This will persist into Tuesday, with dry weather on tap. However, with strong subsidence in place, mostly clear skies, and strong radiational heating, temps will quickly react. While temperatures on Monday will be quite cool after the cold front, temperatures by Tuesday will moderate back into the upper 80s and low 90s. This will set the stage for Wednesday, heading into the Independence Day celebrations, as another day of warming is in the books amidst a strong ridge across the region. However, despite a strong upper level high directly overhead, a cold front will be approaching from the NW, and the surge of llvl S to SW flow will help increase moisture (in addition to temperatures). All models show afternoon convection developing across portions of the state Wednesday. Highs will top out in the low 90s, but the added moisture will increase humidity, making it feel around 100 degrees in many locations. While the pops may back off some Wednesday night with the loss of daytime heating, the cold front will continue to approach, increasing pops once more during the day Thursday as the front lays itself out across the state. Despite the increased clouds and likely pops, the strong WAA into the region will still be one of the main stories, with highs topping out in the upper 80s, but heat indices in the upper 90s - some 10 degrees higher in some locations. By Friday, it`s a bit unclear at this point if the front will dissipate or if it will settle south of the state. However, the models show more zonal WSW flow across the region during the day, with continued high pressure off to our south. Afternoon pop up convection is forecast in nearly all the models, as is the continued heating - despite being in a post-frontal environment. If the current forecasts hold, temperatures on Friday will rise slightly instead of cooling, with highs in the upper 90s and low 90s and heat indices in the mid 90s to around 100 once more. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) ISSUED AT 815 PM EDT FRI JUN 28 2024 VFR conditions will generally prevail through the TAF period. There is a chance of showers and a slight chance of thunderstorms on Saturday, but there is not enough confidence in timing/placement to include it in TAFs beyond an period of VCTS and CBs. River valley fog is expected again late tonight, but these will not affect the TAF sites. Generally, light south to southwest winds will hold through the period - away from any thunderstorms. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...CMC LONG TERM...JMW AVIATION...CMC/GREIF