Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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413 FXUS63 KJKL 052021 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 421 PM EDT Wed Jun 5 2024 .KEY MESSAGES... - Showers and thunderstorms will affect the area today and tonight. - Relatively cooler and drier weather will arrive behind a cold front passing through eastern Kentucky on Thursday. && .SHORT TERM...(This evening through Thursday night) Issued at 420 PM EDT WED JUN 5 2024 Late this afternoon the axis of a mid and upper level ridge extended from off the southeastern U.S. coast across the mid Atlantic states into Quebec. Further west, an upper level low was centered near the Saskatchewan and Manitoba border with an associated trough axis through the MS Valley. A lead shortwave was moving across the OH Valley and TN Valley with shower and some thunderstorms with heavy downpours working across the region preceding it. At the surface, an area of low pressure was located in the Manitoba into Ontario region with the trailing cold front south into the Great Lakes to mid MS Valley to Southern Plains. A secondary cold front extends from western Ontario to the central Plains and then into the western Conus. This evening and tonight, the lead shortwave will depart to the east by early this evening with the next shortwave/500 mb trough axis will continue east across the central and eastern Great Lakes and OH Valley into the Southeastern Conus and the Appalachians. Meanwhile the upper level low to the northwest will meander into Ontario and then to the northern Great Lakes through Thursday. Another shortwave trough will move into the OH Valley on Thursday. The first cold front will work across the Commonwealth and enter eastern KY late tonight and move southeast of the area on Thursday followed by the secondary cold front that nears eastern KY during the day on Thursday and then across the area on Thursday evening. The airmass is rather moist across the region, PW is analyzed in the 1.6 to 1.85 inch range while instability is rather weak with MLCAPE generally around 500 to 1000 J/kg at present, with low level lapse rates of about 6 to 7C/km. Mid level lapse rates are generally weak as well, 6C/km or less. The airmass will remain moist with deep moisture persisting ahead of the front, as PW remains in the 1.5 to 1.8 inch range ahead of the first cold front. MLCAPE is forecast by the RAP to be in the 500 to 1000 J/kg range ahead of the boundary before diminishing later tonight with lapse rates becoming meager. Locally heavy rain will remain the primary threat with any additional convection behind the convection that will depart into WV and VA within the next hour and another area of convection anticipated ahead of the next shortwave trough and the cold front. This second round of convection area of convection should taper off from northwest to southeast late tonight. A drier airmass will be in place behind the first front on Thursday, however, some shallow showers or sprinkles may accompany the secondary front and shortwave on Thursday afternoon and Thursday evening. Some fog will be possible as well tonight with low dewpoint depressions especially if showers end in a location and winds slacken. Fog will probably be more prevalent in the valleys on Friday night behind the secondary front as high pressure begins to nose into eastern KY. .LONG TERM...(Friday through Wednesday) Issued at 333 PM EDT WED JUN 5 2024 We begin the period quiet, as cold front will have passed through the area. In the mid-levels, we see a low set up near the Great Lakes and high set up in the Southern Plains, with solid agreement in the ensembles and deterministic guidance. This will lead to west to west northwest flow at the surface and much drier airmass. This will usher in an airmass that will lead to highs in the upper 70s to lower 80s, which is right around normal for this time of year. This drier weather will extend into Saturday with with highs sticking around 80 degrees. By later Saturday into Sunday, there is good agreement on increasing moisture, as the the mean of the EPS/GEFS/GEPS ensemble models show PWAT increasing toward the 1 inch range. This will be ahead of another southward moving frontal boundary, the a low forms on near the Lower Ohio Valley. This will spark of showers and perhaps a few thunderstorms Saturday night into Sunday, with peak chances on Sunday in the 30-50 percent range. In the wake of this weaker front, we don`t see quite as much of moisture drop off and given a mid-level trough axis hangs around during this time. This could lead to additional chances of showers and thunderstorms on Monday at around the 30-40 percent chance range. The the guidance begins to show divergence in the mid- and upper level pattern. The leads to a fair amount of uncertainty in the forecast for Tuesday into Wednesday. So we will continue to see small chances (around 20 percent or less) of showers and thunderstorms mainly Tuesday and Wednesday afternoon. It looks like much of the period we will see afternoon highs near normal in the mid to upper 70s in most cases. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) ISSUED AT 214 PM EDT WED JUN 5 2024 Showers and some thunderstorms were moving across the region at issuance time as a disturbance works across eastern KY. Periods of reductions to MVFR and IFR and with the heaviest showers briefly to around airport minimums. Thunder on station is most probable in the first few hours at JKL, KSYM, and KSJS. This initial round of showers and thunderstorms will move across the area over the first 3 to 4 hours of the period, before a likely brief lull. Another round of showers and thunderstorms in association with the next disturbance and cold front is expected during the 00Z to 12Z timeframe. However, the predictability of timing these beyond the first 3 to 5 hours of the period is too low to specify it in the TAFs, and VCTS has been used after that point. Winds will average south to southwest at 10KT or less through the first 12 hours of the period, before winds become more westerly to end the period behind the front. Some gusts as high as 25 to 30KT may occur with the stronger thunderstorms. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...JP LONG TERM...DJ AVIATION...JP