textproduct: Louisville

KEY MESSAGES

* Heat Advisory remains in effect for areas generally along and west of I-65. Temperatures in the low 90s combined with very high humidity will create peak afternoon Heat Index values in the 105 - 110F range.

* Strong to severe thunderstorms are possible late tonight into Tuesday morning. Damaging winds remain main threat with any thunderstorm complex.

* Heat Advisory was extended for portions of southern and southwest KY for lingering heat and humidity. Expect high heat and humidity in these areas once again.

* Dry but slightly cooler through mid to late week before shower and storm chances return for the weekend.

SHORT TERM /THROUGH TUESDAY/

Issued at 356 PM EDT Mon Jul 27 2026

Convective clouds along with wildfire smoke in the upper atmosphere has limited some of the heating this afternoon. Per the KY Mesonet, heat index values were around the mid 90s in the advisory with temperatures in the mid/upper 80s and dew points in the low/mid 70s. While heat index values have not materialized to advisory levels yet this afternoon we will keep the advisory in place until 01z with the exception of the counties in our far southwestern CWA where we decided to extend the advisory into tomorrow as model guidance does suggest we could still see lingering heat and humidity in this area through the day tomorrow as heat index values are between 104 to 109.

The other main impact in the short term remains the threat for strong to severe storms associated with a MCS coming out of the Great Lakes and pushing south this afternoon and evening. SPC continues to keep most of our CWA in a Slight Risk (level 2 of 5) with just the southern portion in a Marginal Risk (level 1 of 5) along the KY/TN border with an Enhanced (level 3 of 5) just to our north across northern and central IN into northwest OH.

Current radar mosaic shows two convective clusters to our north. Cluster #1 is across northern IN and seems to have developed a more east-southeast push between South Bend and Kokomo Indiana while cluster #2 is over Lake Michigan angled northwest towards Milwaukee, WI. Cluster #2 has been what most of the hi-res/short range models have been picking up on for our area later this evening into early Tuesday morning.

Current mesoanalysis shows a steep instability gradient stretching from South Bend IN through Fort Wayne towards Cincinnati, OH. Even the deep layer sheer seems to be more to the east-southeast towards Cincinnati, OH. Earlier today you could see on visible satellite the warm front boundary stretching from Lake Michigan towards Lexington. Thinking still remains that we will see a complex of strong storms working towards our CWA later this evening towards midnight with damaging straight line winds being the main threat. Across our far northern CWA from Madison, IN over to Salem, IN the SPC continues to highlight this area in a CIG 1 category for severe winds, which remain reasonable given the history of some of these storms as they worked through northern IL and northern IN.

Some of the potential limiting factors remains how much will cluster #1 work over the atmosphere at it moves across northern and central IN as it moves off to the east-southeast. There will be ample instability across the northern CWA for these MCS to work with and it will depending on the cold pool and the overall forward propagation. SPC has a Severe Thunderstorm Watch to our north that goes until 9pm EDT so current thinking based on the overall short range/CAM model trends is that arrival of these storms is between 9pm to Midnight moving very quickly to the south and the models do seem to have this activity decreasing and weakening as it works south of the parkways.

Activity looks to be finished and out of the area during the pre- dawn hours of tomorrow. A weak cold front will start to push south during the day tomorrow with drier dew points and slightly cooler temperatures. 18z run of the HRRR continues to show more wildfire smoke increasing over southern IN/central KY tomorrow afternoon. Like today, this could limit temperatures with the warmest temperatures across the south and southwest KY.

LONG TERM /TUESDAY NIGHT THROUGH MONDAY/

Issued at 356 PM EDT Mon Jul 27 2026

While we will remain under northwest flow aloft, the upper ridge to the west weakens and flattens allowing us to cool off a bit and see lower dew points in the 60s and highs in the mid/upper 80s. This period looks to be mainly dry through the end of the week.

Our next chance for precipitation appears to be this weekend as a shortwave trough will work over the northern peripheral of the western ridge and then moves into the Ohio Valley. Deterministic models then have this shortwave getting cutoff over the region for early next week.

AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/

Issued at 155 PM EDT Mon Jul 27 2026

As was stated in the previous discussion, the forecast remains challenging but I think the picture is coming into better focus. The main challenge remains timing of a convective cluster of thunderstorms later tonight. This activity will be associated with the ongoing activity along the Great Lakes and around Chicago at this hour. While confidence is growing on timing sometime between 02- 04z there is still questions on locations that could be impacted by these storms. A lot will be decided by the current activity and how it behaves as it moves south through Indiana towards the Ohio River and southern IN. The warm front can be seen on visible satellite from the lingering low clouds from this morning stretching from Lake Michigan towards LEX. Current thinking is this will be the general path these storms take from around Chicago towards SDF and LEX. While confidence is growing still decided to go with PROB30 as there remains some questions on timing and location. Once this passes winds will shift and become more west to even northwest for tomorrow and could see gusts around 20 kts.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for KYZ023>025-027>030-045-053-062-063-074. Heat Advisory until 7 PM CDT Tuesday for KYZ026-061-070>073. IN...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for INZ076>078-083-084-089>092.