textproduct: Louisville

KEY MESSAGES

* Shower and storm chances (40-60%) return Wednesday night into early Thursday. There is a low risk for both severe weather and localized flooding across areas west of I-65 in Kentucky.

* Slight (15-24%) shower and storm chances linger through Saturday across areas mainly east of the I-75 corridor, but most locations look to stay dry.

SHORT TERM /THROUGH TONIGHT/

Issued at 314 PM EDT Tue Aug 18 2026

Early Tuesday afternoon, zonal flow aloft was in place across central Kentucky and southern Indiana, while high pressure was maintaining dry and mild conditions at the surface with temperatures in the upper 70s to mid 80s at 3pm EDT. Meanwhile, satellite imagery reveals increasing mid-high level clouds across the Midwest associated with an approaching disturbance. Tonight, this first shortwave will spark upstream convection which will reach our area in a weakening state tomorrow morning, bringing little (if anything) in the way of rain but numerous clouds which HREF suggests will likely (50-70% chance) stick around through at least mid afternoon. Shower and storm chances look to increase Wednesday night into Thursday morning as a modest kt LLJ overspreads the area ahead of a second shortwave trough, giving us 35-45 kt deep layer shear. The arrival of this better shear during the overnight period when instability (500-1000 J/kg MUCAPE, per HREF) is at its diurnal minimum and a stable layer is present below 940mb should limit severe potential, but marginally severe wind or hail cannot be ruled out west of I-65 where instability is highest and 20km HREF neighborhood probs are highest (10-30%) for updraft speeds > 20m/s. SPC's day 2 outlook features a level 1 of 5 (marginal) risk for severe weather west of roughly I-65. Modest moisture transport via the LLJ and PWATs around 1.7-2 inches (highest southwest) suggest any showers and storms could be efficient rain producers, and NBM probabilities for more than 2 inches of rainfall are generally 10- 25% across western portions of the area. However, many of the CAMs have the main thunderstorm cluster diving southwest of our area which could limit our supply of Gulf Moisture and mitigate the risk of any localized hydrological issues. We can't completely rule out the prospect of flash flooding, but the risk appears low at this point given the soils are drier across southwestern Kentucky which has largely missed out on recent heavy rains.

LONG TERM /WEDNESDAY THROUGH TUESDAY/

Issued at 311 PM EDT Tue Aug 18 2026

Depending on when the front departs to the southeast, we'll have to keep an eye on the potential for redevelopment along it Thursday afternoon when the National Blend of Models (NBM) gives a 20-35% chance for more than 2000 J/kg SBCAPE across our far south. In fact, some guidance suggests the front could lift back north and allow a few showers and storms along/east of roughly I-75 Friday afternoon and evening as well. However, for most of our area, we should have a break Thursday into Friday, with the next system bringing a stronger front and perhaps some shower and storm chances Saturday into Sunday.

Principle Components (PCs) for Empirical orthogonal functions (EOFs) applied to the Low Resolution Ensemble Forecast (LREF) system's 500mb heights suggest the primary source of model spread - and hence, forecast uncertainty - over the weekend is in the depth of troughing over the Great Lakes and Northeast. Deeper troughing, supported by about 40% of LREF membership, suggests a stronger cold front which would bring the area scattered showers and storms followed by below normal temperatures; in addition, stronger kinematics suggest our area could see at least a low (5+%) risk for severe weather with any storms that develop. A weaker trough to our east (the remaining 60% of LREF members favor this solution), by contrast, would favor seasonably warm temperatures through the weekend and low chances for precipitation. In either case, at least a couple days of dry weather can be expected to close the weekend and kick off next work week as northwest flow overspreads the local area in the wake of that trough.

AVIATION /18Z TAFS THROUGH 00Z THURSDAY/

Issued at 123 PM EDT Tue Aug 18 2026

VFR conditions are expected through the current forecast period, with a lingering cu field this afternoon expected to have cloud bases generally between 3-5k ft. Light NW winds are expected this afternoon, with winds going light and variable after sunset this evening. Mostly clear skies are expected overnight, with mid-level clouds increasing from NW to SE in the early morning hours Wednesday. A few light rain showers are possible at HNB by the end of the current forecast period; however, due to low probabilities, will abstain from mention in the current forecast.

LMK WATCHES/WARNINGS/ADVISORIES

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