textproduct: Louisville

KEY MESSAGES

* Heat Advisory 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.

* Additional severe thunderstorms will be possible later this evening into Tuesday morning. Damaging winds will be the main threat with any thunderstorm complex.

* Additional concerns for heat and humidity linger into Tuesday across southern and southwest KY before a cool front pushes through. 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 TONIGHT/

Issued at 324 AM EDT Mon Jul 27 2026

Expecting things to be fairly quiet through the early morning hours as we are seeing the last of the this evening's convective complex let go of southwestern portions of the CWA. Can't rule out some patchy fog, especially for areas that saw some brief heavy rain and are able to clear out before sunrise.

Decided to lift a Heat Advisory for later this morning through late this evening for areas along and west of I-65. Expecting max afternoon heat indices in the 105 to 110F range in these areas thanks to temperatures in the low 90s and very high dew points in the 70s. A few of our far western tier counties may end up peaking around 110F. Tuesday afternoon may also need a Heat Advisory for portions of our western and southern CWA, but will take it one day at a time given the convective complex activity that will be expected over the next 36 hours or so.

The upper pattern remains the same today and tonight as NW flow is sandwiched over our region between the strong upper ridge over the central CONUS, and troughing over New England. We'll be keeping a close eye on the Great Lakes region this morning as a notable shortwave embedded in the NW flow aloft will likely trigger multiple clusters of showers and thunderstorms. Meanwhile, our airmass is expected to steadily recover, and will likely become strongly unstable by late afternoon and early evening. Multiple models suggest we could see 4000+ J/KG of SB CAPE thanks to the hot and moist surface conditions beneath impressive mid level lapse rates. Forecast soundings show some pretty fat CAPE profiles amid seasonably strong deep layer flow. The stronger than normal deep layer shear will be aided by the exit region of a 60-70 knot upper level jet, however the low level speed shear profile is quite weak below 500 mb. This could create an interesting scenario where the upstream complexes gust out pretty quickly once they intensify. Convection will still certainly forward propagate given the amount of instability and each gusty front acting as a trigger. However, the overall cold pool may struggle to consolidate a bit given the more strung out nature of the forward propagation. Think this may end up being a limiting factor to a much stronger widespread wind producing MCS, however do expect that it still could be quite strong getting into our area given the amount of instability and whatever cold pool does get going will aid the lack of low level speed shear a bit.

SPC has added a Cig 1 category to the Wind outlook which seems reasonable. Timing is still somewhat in question given models continue to struggle on precise upstream initiation, and how that initiation then interacts with the NW-SE 700-300mb mean wind, and the more N-S instability gradient. The trend over the past 24 hours has been for convection to be farther W than models are initializing, so do think we'll be in the game, and that a NE solution offered a couple days ago is out of the picture. Right now, thinking the best estimate for timing into our northern CWA is sometime in the 7-10 PM EDT window, then propagating south into KY between 8 and 12 AM EDT. At this point, will likely be messaging pockets of 45+ MPH winds with isolated instances of 75+ MPH (Cig 1) possible, at least across the northern CWA.

LONG TERM /TUESDAY THROUGH SUNDAY/

Issued at 317 AM EDT Mon Jul 27 2026

Tuesday - Friday Afternoon...

A shortwave and its associated surface low will move through the eastern Great Lakes toward New England on Tuesday. A cold front trailing from this feature will slide through our area pretty early in the day, with shower and storm chances shutting down across our east through the day. For now, it looks like any stronger storm activity will develop east of our area, but it does appear there will be a brief warm sector Tuesday morning before frontal passage. So, not completely ready to rule out that we could still see a strong storm or two Tuesday morning before the storm threat shuts down.

Our S and SW CWA will have the longest residence time ahead of frontal passage and are still expected to squeeze out highs in the low 90s. Given that dew points are likely to be in the mid to upper 70s, we'll likely flirt with Heat Advisory criteria along the KY/TN border and across west central KY. Medium confidence we'll need a headline for Tuesday for at least some of the CWA.

The upper pattern through mid to late week will continue to feature NW flow aloft between the central CONUS ridge, and the closed upper low meandering over New England. Overall, looks like a dry stretch as the upper pattern looks void of any notable features/triggers. Temps will be a bit cooler behind the front and will feature highs in the mid to upper 80s each day. Dew points will also be notably lower behind the front, and generally around the low 60s. This will lead to more pleasant nighttime lows mostly in the 60s.

Friday Evening - Sunday...

Our dry stretch of weather likely comes to an end as we head into the weekend. The upper ridge to our west will break down as a shortwave digs on the northern periphery, and will likely slide into the mid Mississippi or Tennessee River Valley for the weekend. Shower and storm chances will be increasing through this time. A bit concerned this could bring a localized flooding threat as it will be a moisture laden and slow moving system. Also don't love seeing a surface low near the area this time of year as it could enhance the low level shear profile a bit. For now, will message shower and storm chances through the weekend with highs in the mid 80s.

AVIATION /12Z TAFS THROUGH 18Z TUESDAY/

Issued at 639 AM EDT Mon Jul 27 2026

Tricky forecast over the next 24 hours as we deal with some fog and low ceilings this morning, followed by VFR later this morning through the afternoon; then a complex of thunderstorms is expected to affect the northern TAF sites late this evening. Seeing a mix of MVFR ceilings around SDF, VFR at BWG/HNB, and fog/low stratus at LEX/RGA at this hour. Things should steadily improve through the morning with a steady WSW or W wind taking hold this afternoon. A t- storm complex is expected to approach from the north tonight and could bring gusty winds to the northern TAF sites. Confidence isn't all that high, so will only mention Prob30 for now.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory from 11 AM EDT /10 AM CDT/ this morning to 9 PM EDT /8 PM CDT/ this evening for KYZ023>030-045-053- 061>063-070>074. IN...Heat Advisory from 11 AM EDT /10 AM CDT/ this morning to 9 PM EDT /8 PM CDT/ this evening for INZ076>078-083-084- 089>092.