Area Forecast Discussion
Issued by NWS Jackson, KY
Issued by NWS Jackson, KY
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719 FXUS63 KJKL 060836 AFDJKL AREA FORECAST DISCUSSION National Weather Service Jackson KY 436 AM EDT Thu Jun 6 2024 .KEY MESSAGES... - Showers and thunderstorms will affect the area again late this evening into the overnight tonight. - Relatively cooler and drier weather will arrive behind a cold front passing through eastern Kentucky on Thursday. && .UPDATE... Issued at 1031 PM EDT WED JUN 5 2024 Showers and thunderstorms are developing and moving into eastern Kentucky from the west, much as predicted by CAMS from earlier today. The main threat from this round of precipitation will be downpours producing isolated areas of high water, especially in poor drainage areas. A few stronger storms are possible, especially with decent 0-1 km storm relative helicity providing some potential for rotating storms. Instability will be a limiting factor, however, especially in areas that were not able to sufficiently destabilize following late afternoon thunderstorms earlier. UPDATE Issued at 550 PM EDT WED JUN 5 2024 With the first round of convection exiting east into West Virginia and Virginia, lowered PoPs and Sky cover grids this evening before the next round of showers and thunderstorms arrive late this evening into the overnight hours. && .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 night through Wednesday) Issued at 436 AM EDT THU JUN 6 2024 The 06/00z model suite begins the long-term period in good synoptic agreement, leading to a high confidence forecast through the upcoming weekend, before increasing model spread results in lower forecast confidence heading into the new work week. Initially, 500H ridging will be solidly in place over northern Mexico and the Southern Plains. Meanwhile two sub-550 dam lows lie in a northwest-southeast oriented trough from the Upper Mackenzie Valley to Lower Great Lakes. Subtle disturbances aloft are riding through the northwest flow over the Central Plains between the ridging further south and the troughing further north. At the surface, a developing wave of low pressure is found over the Dakotas with a trailing cold front across the northern Rockies, while high pressure is meanders east of the 500H ridge across the Lower Ohio/Tennessee and Mississippi river valleys. The surface high pressure will shift east, cresting over the Central/Southern Appalachians late Friday night. As that high continues to press east on Saturday, focus will turn toward the weak low pressure passing through the Southern Great Lakes and dragging a cold front into the Ohio Valley. Meanwhile, the more easterly upper level low (over Quebec) will elongate and rotate toward the Ohio Valley, shoving the cold front south of the Commonwealth and allowing cool Canadian air to pour across eastern Kentucky on Sunday night and Monday. Height rises return Monday night and Tuesday as the trough axis shifts to our east and high pressure passes over the Ohio Valley/Central Appalachians. The second upper level low and/or an associated trough may then impact eastern Kentucky during the middle of next week but the specifics are uncertain due to significant model spread. Sensible weather will feature fair conditions through Saturday along with seasonably cool temperatures. Morning low temperatures are forecast to range from the lower to mid 50s while afternoon highs top out in the mid 70s to lower 80s. A few of the coldest northeastern valleys could briefly dip into the upper 40s early Saturday morning. Shower chances rise again Saturday night as the cold front drops into the Ohio Valley and peak ~40 to 60 PoP as that cold front passes over eastern Kentucky on Sunday. A weak thunderstorm cannot be ruled out ahead of or along the front. Behind that front, diurnally-driven showers (20-30 PoP) are again expected to bubble up on Monday, along with a possible rumble of thunder. After one more day with highs in the mid to upper 70s on Sunday, Monday`s maximum temperatures will be noticeably cooler, primarily in the lower to middle 70s. A few of the cooler locales may fail to even reach 70. A downright chilly night for mid-June is in store for Monday night, likely deep into the lower and middle 50s for most locations and perhaps even in the 40s through the more sheltered valleys and hollows. (Normal highs for June 11th at the lower elevations range from ~79 to 83 while normal lows range from 56 to 64.) Once the high pressure crests overhead, winds will turn southerly on Tuesday leading to a quick warming trend -- high temperatures return to the 80s by Wednesday. && .AVIATION...(For the 06Z TAFS through 06Z Thursday night) ISSUED AT 332 AM EDT THU JUN 6 2024 A band of showers and a few thunderstorms ahead of a weak cold front was over the northern portion of the forecast area at the start of the period and was moving slowly southeast. It will continue its progression, with what`s left of it exiting southeast out of KY around mid day. It will bring reductions to MVFR conditions, which will persist for a time after the passage of the precip and cold front. Localized reductions to IFR may also occur. A return to VFR conditions is forecast during the afternoon. Another area of isolated to scattered showers associated with a second cold front is expected to develop and move through from northwest to southeast this evening. Restrictions below VFR are less likely with the last round of showers and would be expected to be localized. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...CMC SHORT TERM...JP LONG TERM...GEERTSON AVIATION...HAL