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Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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084 FXUS63 KJKL 291740 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 140 PM EDT Sat Jun 29 2024 .KEY MESSAGES... - Hot and humid weather is expected today, with afternoon highs around 90 degrees and heat indices peaking around 100 degrees in some places. - There is potential for thunderstorms today through Sunday as a cold front approaches and moves through. A few storms this afternoon and evening could produce strong wind gusts and heavy rain. - A short-lived break from the heat and humidity is forecast 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. 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 140 PM EDT SAT JUN 29 2024 Early afternoon update lowers PoPs to isolated to widely scattered through this afternoon, but raises PoPs for the overnight as the 12z CAMS appear consistent in moving one or more thunderstorm clusters northwest to southeast across the forecast area this evening into the overnight. Activity may remain confined to primarily shower activity through much of the afternoon, as some CAMS depict a warm layer at around the 750-hPa level that may inhibit deeper convection. There is also a lack of forcing in the atmosphere to help organize convection. However, as we approach sunset this evening and through the overnight, better forcing plus upstream convection will likely impact the forecast area, especially along and north of the Mountain Parkway. UPDATE Issued at 1046 AM EDT SAT JUN 29 2024 Minimal changes were made with the late morning update. Left PoPs as-is for today with just minor tweaks to Sky grids for the midday period based on latest observed satellite trends. Also blended in latest observations for a seamless transition to the forecast. UPDATE Issued at 735 AM EDT SAT JUN 29 2024 Based on obs, only made minor changes to sky cover and temperatures during the morning. && .SHORT TERM...(Today through Sunday) Issued at 510 AM EDT SAT JUN 29 2024 A series of shortwaves will maintain a broader upper level trough moving east across the Midwest, northeast CONUS, Ontario, and Quebec this weekend. We will be on the southern edge of the prevailing westerlies aloft associated with the trough. The trough will support a surface cold front which will approach today and tonight and then pass through from northwest to southeast on Sunday. Low level southwest flow ahead of the front will carry warm and humid air across the region. Forecast soundings show an uncapped atmosphere as heating occurs today, and thunderstorms are expected to bubble up. Features are weak with little to focus development, and winds aloft are unimpressive with nothing more than 20-30 kts below 500 mb. However, what flow there is should yield enough cell movement to give decent precip coverage in the end, and a likely POP was used for the afternoon/early evening. With the weak features, will look for convection to wane during the night. The cold front will move southeast through the forecast area on Sunday with a similar atmospheric set-up ahead of the front. Southeast KY won`t have fropa until late Sunday and stands the best shot at seeing more thunderstorms, while the northwest part of the forecast area is likely to have fropa before sufficient heating to support development. .LONG TERM...(Sunday night through Friday) Issued at 510 AM EDT SAT JUN 29 2024 Models are in good agreement with the main synoptic features and pattern evolution aloft through the extended. Low amplitude trough will be passing from the Great Lakes through the Upper Ohio Valley and New England at the start of the period. Southern CONUS ridging aloft will shift eastward and amplify as the center of the high transitions to the southeastern CONUS. This results in ridging building over our region within 24 hours of the start of the period. Ridging remain generally over the eastern CONUS through the first half of the extended. Short wave energy then begins to ride across the northern periphery of the ridge and suppresses it southward through the latter half of the extended, putting eastern Kentucky under an increasing threat of unsettled weather with each passing day. At the surface, Canadian high pressure will move into the region behind an exiting surface cold front, transiting the Ohio Valley, moving from the Upper Midwest to the east coast by Wednesday. Thereafter, southerly return flow kick in for the remainder of the forecast window. Sensible weather features a continuation of seasonably hot, muggy weather in general. However, the Canadian high pressure system will provide another temporary (day or so) break from the summer heat and humidity (lower dew points) from Sunday night through Tuesday morning. This brief cool off will be very similar to the recent 1-2 day breaks from the humid, hot summer weather we have experienced on and off over the past few weeks. Southerly flow will bring moisture back into the area by midweek. Combined with the heat, the muggy conditions will make our environment ripe for additional shower and thunderstorm activity through the latter half of the extended. For hazards, afternoon MLCAPES increase to between 1000 and 1500 J/kg on from Wednesday through Friday. However, as has often been the case of late, bulk shear is marginal at best, less than 25 kts on Wednesday and Thursday. The exception is our Bluegrass Counties, where the shear creeps up to around 30 kts late Thursday. Bulk shear increased more readily across the entire area by Friday, to around 30 kts. Thus while there will be the potential for strong to severe storms, prefer to see overall better bulk shear (35 kts or more) for the stronger more widespread or organized convection. In addition, mid-level lapse rates and wind fields are rather unimpressive. Thus at this time, any severe thunderstorm potential will be limited and generally restricted to a wind threat. PWATS increase to around the 90th percentile of climatology by Thursday and Friday. Therefore can not rule out some locally heavy rain, especially with any stronger storms. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) ISSUED AT 132 PM EDT SAT JUN 29 2024 Showers and thunderstorms will impact the TAF sites at times through the period. Main window of concern is between 00z and 12z with one or more thunderstorm clusters depicted by high-resolution mesoscale models. With a clear trend in these models, decided to be a little more on the aggressive side with timing TSRA activity this evening into the overnight. Meanwhile, until around 00z expect more isolated to widely scattered showers and thunderstorms. The spotty nature of this activity precludes anything other than a mention of VCTS at this time. A few storms could be strong to severe and produce gusty winds. If rain/thunderstorms impact TAF sites and there is any partial clearing by dawn, fog will likely impact those TAF sites. Aside from fog and precipitation, VFR conditions are expected. Light but occasionally gusty southwest winds will gradually diminish into the overnight, then become northwesterly late in the TAF period at KSYM as a cold front bringing much cooler and drier air begins to move across the area from northwest to southeast during the day Sunday, mostly after 18z. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...CMC SHORT TERM...HAL LONG TERM...RAY AVIATION...CMC