Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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796 FXUS63 KLMK 242335 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 735 PM EDT Fri May 24 2024 ...Updated Aviation Discussion... .KEY MESSAGES... * Stormy pattern with risks of strong to severe storms and localized flooding issues will continue into Monday. * The greatest threat for severe weather will likely come Sunday afternoon into Sunday night ahead of a cold front. Severe storms will be capable of producing damaging winds, large hail, and tornadoes. && .SHORT TERM /THROUGH SATURDAY/... Issued at 326 PM EDT Fri May 24 2024 Currently, a cold front stretches from eastern Iowa south-southwest back through Oklahoma City and continues on through Texas. Ahead of the front, 5-10 mph southerly winds are keeping precipitable water values mostly around 1.25" over the Lower Ohio Valley. Some pooling in the area will cause pockets of 1.5" values, so we have plenty of moisture in place with dew points ranging from the mid 60s to low 70s. Even after parts of southern Indiana and central Kentucky saw clear skies earlier this morning, most areas now are seeing some level of cloud cover debris from convection over western Kentucky and Tennessee. This hasn`t limited instability too much as SPC`s mesoanalysis currently shows 1,000 to 2,000 J/kg of MLCAPE over the CWA, and over the next few hours, these values could grow 500 or so more. With that being said, there is no shear. Deep layer, 0-6km bulk shear, values are around 10 knots, so any thunderstorms today would be limited in their development potential. For the rest of this afternoon and evening, many areas will likely remain dry, but a broken line of convection, that is currently stretching northwest to southeast over the CWA, is expected to continue to the east. Any development could produce lightning and some gusty winds. Severe weather isn`t expected, but a warning or two is possible. Tonight, as the earlier line of convection is ending in eastern Kentucky, convection ahead of the front is expected to dive southeast across southern Illinois and far southwest Indiana as it travels towards the Lake Cumberland region. Being that the line is expected to arrive after midnight, any storms should be elevated, so winds will be less of a threat. Some hail could still be possible before the line exits the region during the predawn hours. Believe skies will remain cloudy for most of the night which will help limit fog development. Some patchy fog will be possible, but not expecting the widespread dense fog like we saw this morning. Lows are expected to remain near normal in the low to mid 60s. Tomorrow, the cold front should make it to near the Ohio River between Indiana and Kentucky before it stalls. Precipitable water values will remain slightly over an inch, and dew points will reach the mid 60s. As high pressure tries to make it into the region, winds throughout the day will begin veering towards the west and northwest as skies become mostly sunny. This will help to begin to dry the region. Can`t rule out some low chances for precipitation, but it should be a dry day after the early morning precipitation exits southern Kentucky. Highs should reach into the low 80s. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... Issued at 326 PM EDT Fri May 24 2024 Some isolated showers and storms may linger into the early parts of the overnight hours Saturday but should steadily taper off toward midnight with a strengthening nocturnal inversion. The rest of the overnight hours are shaping up to be fairly quiet. By dawn Sunday morning, a strong LLJ will begin nosing in from the west. Some scattered showers and storms could accompany the arrival of the LLJ, but more notably, we`ll gradually see an uptick in low level moisture through the day as the LLJ overspreads the region and the stalled frontal boundary across northern portions of the CWA lifts northward as a warm front. By the afternoon, we should see some clearing/drying within the warm sector of an approaching low/cold front. Models predict very unstable conditions as increasing low level moisture and steepening low/mid level lapse rates result in MLCAPE surging into the 2,000 to +3,000 J/KG range. Environmental low level and deep layer shear will also increase due to the presence of the LLJ and an approaching upper level trough. Forecast soundings from most models reveal a fairly stout capping inversion near 750-700mb, which will serve to limit convective development. Forecast models vary on afternoon storm initiation, with some keeping the cap strong enough to hold off convection, while others initiate isolated convection along weak mesoscale boundaries. Should storms overcome the cap during the afternoon in this environment, they would be capable of damaging winds, very large hail (+2"), and tornadoes. Better forcing for storms looks to arrive Sunday night as the surface cold front approaches from the west. We could see one (or multiple) waves of convection ahead of the front and the convection could consolidate into one large squall line. Damaging winds, large hail, and tornadoes would be possible with severe storms. Storm severity will be somewhat dependent on a couple of factors, including: (1), the strength of the capping inversion overnight, and (2) if we end up in a scenario where we have multiple rounds of storms, will we destabilize enough in the wake of the first round to support severe weather for subsequent rounds? The cold front should begin pushing into the region Monday morning ending the severe threat. Isolated/Scattered showers and perhaps a storm could develop during the daytime hours but drier air will gradually filter in from the northwest so rain chances should steadily decrease by Monday night. Much of next week will feature cooler than normal temperatures with more comfortable dewpoints and mostly dry conditions. && .AVIATION /00Z TAFS THROUGH 06Z MONDAY/... Issued at 734 PM EDT Fri May 24 2024 Impacts/Confidence: - Low confidence in timing and coverage of overnight precipitation - Medium confidence in MVFR ceilings Saturday morning Discussion...Tonight VFR conditions will deteriorate tomorrow morning as a cold front moves and eventually stalls over the forecast area. Early evening radar highlights two areas of ongoing storm activity: a recently develop set over the Bluegrass and fairly disorganized cluster tracking across southern Illinois. Of the two, the latter is the most concerning as it will continue moving east- southeast and approach the TAF vicinity around midnight. Based on current model guidance, BWG will be the most likely terminal to have any impacts from the aforementioned cluster with low confidence in any eastward extension. As a result, any storm-related impact at HNB and SDF will be addressed with AMD if needed. Otherwise, expect winds turning from the south (tonight) to the west-northwest (tomorrow) as the actual cold front sinks in while ceilings fall to MVFR thresholds. VFR conditions will return tomorrow afternoon. Extended Outlook.. Advection fog/stratus cannot be ruled out Saturday night as the front lifts to the north. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ SHORT TERM...KDW LONG TERM...DM AVIATION...ALL