Expires:No;;886184 FXUS63 KLMK 090525 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 125 AM EDT Thu May 9 2024 ...Updated Aviation Discussion... .KEY MESSAGES... * Scattered severe storms possible this evening. All severe hazards will be possible. * Flooding concerns increasing for southern and central Kentucky. A Flood Watch is in effect through Thursday morning. * Below normal temperatures return by Friday and persist into the weekend. && .UPDATE... Issued at 1248 AM EDT Thu May 9 2024 The tornado watch has been allowed to expire and the flood watch remains. Currently, showers with some embedded isolated lightning is moving east over the region. To the west, a line of strong storms is approaching the region. These storms have had a history of gusty winds and small hail. This line will continue to move along a MUCAPE gradient and take advantage of ample Effective Bulk Shear. Limiting factors to this line maintaining into central Kentucky is the CIN and worked over environment. Convection will likely be elevated. There does remain a threat for flash flooding and flooding. Many rounds of entraining and back-building storms has lead to around 4 inches of rain in our southern tier of counties. This next round of storms will lead to an additional 0.5-1.0 inches of rain or locally up to 1.5 inches. Tall, skinny and elevated CAPE with PWAT climatological maximum of around 1.8 inches will lead to proficient precip production. Motorists should use caution, flooding at night is very difficult to see. && .SHORT TERM /THROUGH THIS AFTERNOON/... Issued at 337 PM EDT Wed May 8 2024 ===================== This afternoon and evening ===================== A MCV is located near St. Louis this afternoon, evolving slowly eastward. An effective warm front/remnant outflow boundary extends SE through portions of western and southern KY, with sfc dewpoints near 70 F along and south of the boundary. Scattered thunderstorms have developed in south-central KY along the boundary and associated instability gradient. Portions of south-central KY have been the slowest to destabilize in the wake of morning convection and cloud debris. Sfc temperatures are only now warming into the lower 70s at BWG, with mid/upper 70s to near 80 noted across southern IN and the northern half of KY. Likely still have a shallow low-level inversion present across south-central KY, where ongoing impressive supercellular storms could be elevated. However, this is also along a boundary/instability gradient which continues to drift northeast with time. A long, straight hodograph above 1 km is also supporting splitting supercells which we have already seen with a left-mover tracking northeast through Ohio County and a right-mover now moving east across Warren County. Storms that move further to the right (E, ESE) will realize greater low-level SRH and have a better chance of producing a tornado. A Tornado Watch has been issued for portions of central and southern KY where the near-term tornado risk is highest - roughly southwest of a line from Brandenburg to Campbellsville. Further north and northeast, low-level winds are notably weaker and the tornado risk is lower. The scattered storm activity ongoing now is expected to continue to drift east and northeast with time, while increasing in coverage this evening. So while severe weather is still very much possible further north, such as along the I-64 corridor, the window for storms and severe weather is shorter. The most likely time frame for severe weather is now (3-4 PM) through Midnight. But areas further northeast, such as from Louisville to Lexington, have the best chance at seeing a severe storm from 5-11 PM EDT. Given the destabilizing airmass (1000-2000+ J/kg MLCAPE) and very strong effective deep layer shear (50-60 kt), supercellular storm modes are likely well into the evening hours. Increasingly larger clusters and perhaps bowing segments will be possible beyond 8 PM. All severe hazards remain possible through the evening hours, with the highest risk in the Tornado Watch area (this includes large hail, damaging winds of 70+ mph, and tornadoes. A Flood Watch also remains in effect for much of the area. Again, the highest risk for flash flooding is concentrated across the southwestern half of the CWA where the greatest thunderstorm coverage is anticipated. Will need to watch closely for any training along the boundary as it slowly lifts northeast. PW values are also highest, exceeding 1.5 inches, along the lingering boundary. 1-3 inches of rain will be possible, with the highest amounts across south-central KY. Localized higher totals of 3+ inches cannot be ruled out across south-central KY. ===================== Tonight and tomorrow ===================== A final band of showers and storms will likely push southeast across the region late this evening into tonight ahead of the cold front. Confidence in severe weather after Midnight is much lower, but localized damaging winds cannot be ruled out. Waning instability will help to limit the wind threat at ground level. This activity will likely weaken with time as it exits from NW to SE by the early morning hours. Thursday looks drier with morning lows in the 60s and afternoon highs near 80 F. && .LONG TERM /TONIGHT THROUGH WEDNESDAY/... Issued at 337 PM EDT Wed May 8 2024 By Thursday evening, the cold front responsible for recent inclement weather will be off to our east along with most, if not all, convective activity. Aloft, a positively tilted longwave trough will extend from the NE US to an upper low positioned over the Four Corners region of the SW CONUS. Embedded shortwave energy will propagate through the longwave pattern into the OH Valley during the day Friday, coupled with wrap-around moisture from the departing surface low, and resulting in lingering precip chances. GFS soundings suggest fog/stratus potential Friday morning; furthermore, 12Z NAM3k and HRRR soundings also show a saturated layer from just above the surface to around 800/750mb, indicative of the possibility of drizzle across southern Indiana and north central KY until late Friday morning. With the upper trough positioned over the OH Valley, temperatures through the weekend will be several degrees below normal, resulting in more of a Springtime feel: looking for daily highs in the upper 60s to low 70s through the weekend. Another shortwave will makes its way through OH Valley Saturday, bringing another chance of light showers as well as tightening the pressure gradient enough to produce some breezy conditions, with gusts expected in the 20-25 mph range Saturday afternoon. Low level ridging will simultaneously begin building into our region Saturday, which would suggest dry conditions for Sunday. Low amplitude upper level ridging will pass overhead to start the workweek, as the low level high center passes to our east. This leaves our region on the dirty side of the high with return flow and an uptick in low level moisture. Rain and storm chances return as early as Monday evening through Mid week. Not expecting a washout, but long range models' low temporal resolution have yet to resolve finer details. It's worth repeating though that CIPS/CSU/SPC severe comparisons show no signs of severe weather during this timeframe. && .AVIATION /06Z TAFS THROUGH 12Z FRIDAY/... Issued at 125 AM EDT Thu May 9 2024 Main threat of severe weather seems to be over with the exception of BWG where there remains a chance of strong winds and hail through the first couple of hours of forecast as a complex of showers and thunderstorms current stretching from Vincennes, IN to Evansville, IN down to around Clarksville TN continues to push eastward. This could bring TAF sites some showers and a few thunderstorms with the strongest of storms as mentioned above for BWG between around 08z to around 11z. These storms could bring a period of gusty winds, lightning as well as some brief VIS and CIG issues from MVFR to IFR. Once the rain and storms pass mid clouds may hang around before a cold front sweeps through late morning to around midday. This will bring a period of MVFR flight categories for a couple of hours and cause a wind shift from the south to more westerly. Winds will be breezy and gusting to around 20-25kts through the afternoon with a return of VFR CIG by afternoon and evening. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...Flood Watch until 8 AM EDT /7 AM CDT/ this morning for KYZ023>043-045>049-053>057-061>067-070>078-081-082. IN...Flood Watch until 8 AM EDT /7 AM CDT/ this morning for INZ077>079-084-089>092. && $$ UPDATE...SRM SHORT TERM...EBW LONG TERM...CRG AVIATION...BTN