textproduct: Louisville

KEY MESSAGES

* Scattered storms linger through this evening, mainly in south- central Kentucky. Storms could produce gusty winds, torrential rainfall, and frequent lightning.

* Scattered to numerous showers and thunderstorms are likely Saturday, which could result in some instances of flash flooding.

* Active weather pattern will continue Sunday through Tuesday, with episodic bouts of showers and storms. Excessive rainfall and flooding will be possible in areas that see repeated rounds of storms.

* Hot and very humid mid to late next week, with peak afternoon heat index values well over 100. Heat indices of 105-110 are possible.

SHORT TERM /THROUGH SATURDAY/

Issued at 334 PM EDT Fri Jul 18 2025

A quasi-stationary boundary lingers from ENE to WSW across north- central KY this afternoon, with ongoing scattered convection in a very moist, unstable environment south of the boundary. Anomalous PW of 2.0-2.2 inches is still noted across the region along this boundary, which is supporting high rainfall rates (briefly exceeding 1-2 in/hr) in any and all convection. Fortunately, large scale forcing is nonexistent today with only weak background height rises aloft. Thunderstorm coverage is more scattered in nature compared to yesterday, with a reduced overall flooding threat due to the lower coverage and reduced training potential. However, some isolated west to east training remains possible across south-central KY. Very localized flash flooding is possible in any areas that see training convection.

Temperatures continue to warm into the 85-90 degree range outside of storms. This is producing heat index values of 95-100 due to the oppressive humidity still in place. Showers and storms will decrease in coverage tonight, but isolated activity will remain possible through most of the overnight period. Temperatures will drop back into the low to mid 70s.

Saturday, a mid-level wave/MCV will move across IL and IN. Hi-res models continue to point to a rather large complex evolving southeast across portions of IA and IL. As these storms push southeast, scattered convection appears likely to develop out ahead of it across southern IL/IN during the mid to late morning hours. This will likely enhance rainfall totals along and just north of the I-64 corridor through the morning and early afternoon hours. Given yesterday's (Thursday) heavy rain footprint and reduced FFG, there is concern for scattered instances of flash flooding across southern IN and north-central KY. Considered a Flood Watch for the northern CWA. However, there is enough uncertainty in the hi-res CAM output for the PM hours to hold off on a watch at this time. Convective evolution Saturday afternoon and evening is messy/problematic, but scattered to numerous showers and storms do appear possible. PW values lingering between 2.0-2.2 inches will support very efficient rainfall production, and any training will boost the flooding risk.

LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/

Issued at 334 PM EDT Fri Jul 18 2025

Sunday into early next week, an upper level ridge will remain over the Southeast with our region residing along a baroclinic zone. A very warm, humid airmass will linger across the region. An extremely moist airmass will remain in place across the region with PW values near 2 inches.

As we move into Sunday, the upper level ridge looks to retrograde slightly to the west with heights building across the Plains. This will allow our upper level flow pattern to become increasingly more northwesterly with time. The overall baroclinic zone will shift from a zonal type regime to a northwest-southeast oriented one from the Midwest down into the eastern Ohio Valley. With our region remaining on the periphery of the southeast ridge, we'll have to watch for more MCVs and perturbations that will bring clusters of showers/storms to the region mainly in the Sunday through Tuesday period. Storms during the period may be strong to marginally severe with mainly a wind damage threat due to waterloaded downdrafts. The storms will also be capable of torrential rainfall and the repeated nature of heavy rainfall potentially training over the same areas may result in an enhanced flood risk across portions of the region. Daytime highs will be in the mid-upper 80s to near 90 with overnight lows in the lower-middle 70s.

By Wednesday of next week, there continues to be an increase in forecast confidence that the mid-level ridge will start to expand and shift the storm track away from the region. While that will lower the heavy rainfall potential, it will also result in an increase in temperatures with no relenting of the humidity. Highs by mid-late next week will warm daily into the low to mid 90s. Dewpoints will remain in the low to mid 70s, resulting in afternoon heat indices well above 100. There is a concern for multiple days of excessive heat, which will increase the risk for heat-related illnesses.

AVIATION /18Z TAFS THROUGH 00Z SUNDAY/

Issued at 150 PM EDT Fri Jul 18 2025

BKN MVFR stratus is finally lifting and trying to SCT out a bit. Prevailing VFR is likely after 18-19Z outside of thunderstorms with light winds. SCT TSRA will continue through the evening, especially across the southern half of central KY. BWG and RGA are most likely to see brief TSRA impacts, including IFR vis, brief torrential rainfall, gusty winds, and frequent lightning.

Convective activity will weaken and become more isolated after sunset this evening. Some shower and isolated TSRA activity looks possible at HNB and SDF early Saturday morning, but the greatest TSRA chances will come late Saturday morning through the afternoon hours. Another round of MVFR clouds looks possible mid to late Sat morning.

LMK WATCHES/WARNINGS/ADVISORIES

KY...None. IN...None.