textproduct: Louisville

KEY MESSAGES

* Sight risk for severe storms later tonight, mainly west of I-65, as a cluster of thunderstorms dive south out of IL/IN and into western KY. Damaging winds are the greatest concern tonight.

* Lower confidence forecast for temperatures and heat indices tomorrow due to the morning thunderstorms and potential cloud cover. A Heat Advisory is still being considered for Monday, but confidence remains low.

* Additional severe thunderstorms will be possible late Monday night and into Tuesday morning. This cluster of storms could be mainly for southern IN and northern KY, but the exact track of these storms remain unclear.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 338 PM EDT Sun Jul 26 2026

It has been a relatively quiet day across the region, with some rare July drizzle earlier this morning, and still dealing with some pesky low stratus over a large portion of the forecast area this afternoon. This increase in cloud cover has slowed down the temperature climb today, with some areas north of the WK/BG Pkwys possibly underachieving on forecast temps today. However, more sunshine has been able to break through in our south, and the KY Mesonet clearly shows the warmer temps in the south. Heat index is close to advisory in our southwest with upper 90s at some locations. However, there is a notable spread of heat index across the state, from the mid-70s in he Bluegrass to the upper 90s in the south.

We've got a very complicated forecast ahead, with multiple hazards possible, with some hazards conditional on how other parts of the forecast play out over time. We'll break down the different components of the forecast below.

===== Slight Risk for Severe Storms Tonight =====

SPC has upgraded the D1 outlook to a slight risk for half of the forecast area, mainly for locations along and west of I-65 for tonight. Multiple areas of strong to severe storms will be possible this evening and throughout tonight from near the MS River into IL/IN/KY/TN. This area has seen the best heating of the day, with temps reaching the upper 80s to lower 90s, along with dewpoints pushing into the lower 80s. This has allowed incredibly strong destabilization to occur today, with SPC Mesoanalysis showing upwards of 7000 J/kg SBCAPE across southeastern MO. Additional convection developing later this afternoon will likely fully realize the favorable thermodynamic environment (characterized by SCP values of 8-12) draped across central IL into the lower OH Valley. Guidance continues to depict relatively quick upscale growth into an organized MCS by early evening with an attendant threat for severe winds into western Kentucky overnight.

While damaging straight line winds are the primary concern tonight, there could be a low end tornado threat as well. Some CAMs should some enhancement of the 0-1km SRH over 100 m2/s2, though this remains a lower confidence tonight. Timing of severe potential through our area will be between 9pm to 5am, with the Slight Risk reasonably placed in our area.

===== Potential for Heat Advisory Monday =====

Perhaps the lowest confidence of the overall forecast revolves around the temperature forecast for Monday, which is also conditional on how the thunderstorm activity plays out. There is concern for temperatures to climb into the lower 90s tomorrow afternoon, with dewpoints in the upper 70s west of I-65. This would yield heat indices of 104-110 in our western third of the forecast area, roughly from Allen (KY) to Washington (IN). However, the early morning convection and possible cold pool could start the day off cooler than currently forecast, leading to our afternoon temps to never reach the forecast highs that are a concern. There is also some potential for additional precip throughout the day as the CAMs suggest additional weakening convective clusters to move into the area from the north, would also add to the derailment of the temperature forecast by adding more cloud cover and precip to the area. With all that said, there was considerable debate on issuing a Heat Advisory for the aforementioned area with this forecast, but confidence just is not where it should be to issue one. Considerations will continue through the evening and overnight as we get more runs of the CAMs and hopefully better confidence.

===== Severe Risk for Monday =====

Another MCS may be possible Monday night into Tuesday morning, which could cause additional damaging winds for a portion of the forecast area. The RRFS appears to be initializing the best, and appears to be favored based on the D2 SPC Outlook. We could see another convective cluster develop over the Great Lakes and punch south- southeast through the Ohio Valley late Monday night or early Tuesday morning. Our northeast corner will have the best chance for severe storms, as indicated by the Slight Risk in D2. Frequent lightning, torrential rainfall, and localized flooding could become a concern as storms roll through. Overall, the track of this MCS remains conditional, but there is growing confidence on severe potential for at least some part of our area for this time frame.

LONG TERM /TUESDAY THROUGH SUNDAY/

Issued at 338 PM EDT Sun Jul 26 2026

===== Tuesday - Thursday =====

The upper ridge remains in place to the west for the middle of the week, with persistent NW flow across the Ohio Valley. Tuesday will feature a sharper mid-level shortwave pivoting across the Great Lakes and into the Northeast, and will influence a sfc low to follow a similar track. A trailing frontal boundary will sweep through the Ohio Valley, and will be the focus for additional showers and storms on Tuesday, with the greatest severe risk just east of the forecast area. Despite a lower confidence in forecast temps for Tuesday, we should still be able to achieve some strong heating combined with increased humidity to support strong destabilization through the afternoon. PWATs near 2 inches are also expected, so heavy rain rates along with some stronger thunderstorms are possible in the afternoon. Steering flow should be slightly more by then, so storms likely will be a bit more progressive to alleviate flooding concerns some. Forecast temps have been knocked down from the NBM, but still have upper 80s to lower 90s, combined with sfc dewpoints in the upper 70s, which could yield heat indices around 100F. There could be a need for a Heat Advisory, but confidence in that remains very low given the precip forecast which could derail our temp forecast.

Our weather turns drier for the Wednesday-Thursday time frame as sfc high pressure settles across the upper Midwest. However, the upper ridge to the west will begin to show signs of weakening by then, though we'll still be in weak NW flow for the time being. Temps for both days will be near normal in the upper 80s, with slightly lower dewpoints.

===== Friday into the Weekend =====

Scattered showers and storms could make a return for Friday and into the weekend as a compact upper low finally disrupts the upper ridge and moves across the central US. There is decent agreement between the GFS/ECMWF for the upper low to come spinning over the Wabash Valley over the weekend, which could keep us slightly more active over next weekend.

AVIATION /18Z TAFS THROUGH 00Z TUESDAY/

Issued at 144 PM EDT Sun Jul 26 2026

Dealing with MVFR cigs today and patchy DZ, which has also dropped vis at times. Plan for a drier afternoon and evening with less interruptions to vis, and should see a gradual improvement on the cigs as well by this evening. However, scattered thunderstorms are possible for most terminals, with LEX and RGA the only sites expected to be drier overnight. However, they are most likely to see several hours of MVFR or IFR cigs and potential lowered vis tomorrow morning from BR. Other terminals will have a PROB30 for TSRA overnight, and generally VFR through tomorrow afterwards.

LMK WATCHES/WARNINGS/ADVISORIES

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