textproduct: Louisville

KEY MESSAGES

* There is a level 3 of 5 (enhanced) risk for severe weather this evening north of a roughly Bedford, Indiana to Richmond, Kentucky line, with the risk decreasing further southwest. Damaging winds, some significant (> 75 mph), are the primary hazard.

* Repeated rounds of heavy rainfall in thunderstorms tonight and again tomorrow could result in localized flash flooding. There is a level 2 of 4 (slight) risk for excessive rainfall.

* Additional rounds of storms are possible (40-60% chance) through Friday. There is a level 2 of 5 (slight) risk for severe weather tomorrow west of I-65, with damaging winds the primary concern.

* Outside of storms, heat indices are likely (50-80% chance) to surpass 100 degrees west of I-65 each afternoon through Thursday, and area-wide over the weekend.

UPDATE

Issued at 250 PM EDT Tue Aug 11 2026

Severe Thunderstorm Watch #568 has been issued until 8 PM EDT for areas along and northeast of a Scottsburg, IN to Winchester, KY line. This complex does have a history of producing wind damage across IN and Ohio.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 223 PM EDT Tue Aug 11 2026

Upstream complex over central IN/OH is now quickly racing SE with a history wind damage. This bowing segment is moving into a strongly unstable environment characterized by 3000-4000 J/KG of ML CAPE and deep layer shear around 30-40 knots. This should allow for a decent cold pool/updraft balance to sustain forward propagation into our NE CWA this afternoon through early evening. Best chance for severe storms capable of damaging winds will be along and east of a Madison, IN to Richmond, KY line as the complex dives SE on the notable CAPE gradient offered by the 11/17z SPC Mesoanalysis. Although damaging winds is the main threat, can't rule out a brief spin up on the leading edge. This would be more likely for any portion of the line oriented more N-S as the 0-3 km shear vector is mostly W-E. Not sure how likely this is given the pretty good southward surge of the cold pool, but nevertheless will keep an eye out for any brief mesovortice potential.

There is much uncertainty with regard to how much convective activity will occur to the west of the geographic line mentioned above. Latest runs of the HRRR suggest that this initial wave is quite progressive and then re-initiation of storms occur in a more N- S fashion along the western flank of the outflow boundary up over SE IN and SW Ohio through the overnight. This is where most concern for a Flash Flood threat could develop. Confidence remains low in this scenario, mainly with respect to placement of that heavy rainfall axis. It will be close whether that threat is able to be realized into our CWA or stays just to the NE. Do have the Flood Watch up to account for this along and east of a Madison, IN down through Richmond, KY line. 11/12z HREF does still suggest that some localized amounts over 3" of rain will be possible with this setup in the PMM data, which closely matches the higher end QPF amounts offered by the highest ensemble member. Something to keep in mind, and it could lead to a few serious Flash Flood concerns if it trains/persists over the same area with the low level jet feeding into a stationary boundary. Confidence is low, but potential is also there.

Much uncertainty for the evolution of things going through Wednesday as much will depend on what happens this evening and tonight. Confidence is fairly high that we will see another convective complex later tomorrow afternoon or evening as it initiates upstream thanks to another shortwave embedded within the NW flow aloft, and then propagates SE through what should be an unstable and overall favorable wind shear environment. Damaging winds would again be the main threat, but a flooding threat could also develop, especially if we get a good amount of rain tonight. Assuming the convectively reinforced outflow boundary is pushed somewhat farther SW after this evening's activity, then it makes sense that tomorrow's threat is also a bit farther southwest as seen on the Day 2 SPC Outlook.

Current Heat Advisory looks pretty good, and don't plan to make any adjustments to that given current obs for this afternoon. May still need to expand the Advisory into Wednesday, but would like to have more confidence in how tonight's convective evolution plays out before committing to a headline tomorrow.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 223 PM EDT Tue Aug 11 2026

Thursday - Friday Night...

The upper ridge will center over the lower Mississippi River Valley/Gulf Coast states for the late week time frame, with the Ohio River Valley sitting on the NE periphery of this feature. NW flow aloft will be in place over our area, sandwiched between the upper ridge and a NE CONUS/Eastern Canada trough. This setup will put us in position for continued MCS potential as we get the overlap between strong instability and notable deep layer shear for this time of year.

In addition to a potential severe weather threat (mainly damaging wind), any repeated rounds of MCS activity could create or exacerbate flooding concerns, depending on what happens through mid week.

Heat and humidity could also continue to be a concern as temperatures could warm into the low and mid 90s in conjunction with low and mid 70s dew points. This will remain low confidence however, given the potential for MCS activity to wreck a temp forecast Thursday or Friday. Will handle any needed Heat Advisory headlines a day at a time in this pattern. Most likely areas for any headlines would be across our SW CWA, closes to the center of the upper ridge.

Saturday - Sunday...

The upper ridge strengthens to around 600 dam at H5 through the weekend, and also centers more over the Ozarks region by this time. This will put our area more solidly under the influence of the subsident airmass associated with an upper ridge, and also slightly more intense heat. In fact, low and mid 90s from late week could give way to mid and upper 90s by Sunday. Some heat headlines look to be a good bet for at least our western or southwestern half of the CWA, if not most of the CWA.

The good news is that this should give us some reprieve from any MCS activity as that threat would shift to the north and east thanks to the movement of the upper ridge.

Monday - Tuesday...

The upper ridge should retrograde back toward the Red River Valley by early next week, with NW flow aloft taking back hold of our area as the NE periphery of the upper ridge retreats. This will allow a weak frontal boundary trailing from a New England system to drop into our region. Some mainly diurnally driven convection could occur with this weak frontal passage on Monday, however we will likely be post-frontal on Tuesday with high pressure building in behind it. Likely a dry forecast for Tuesday unless the front gets hung up. Pretty good agreement right now that it makes it through so will lean toward dry and overall cooler temperatures by Tuesday.

AVIATION /18Z TAFS THROUGH 00Z THURSDAY/

Issued at 125 PM EDT Tue Aug 11 2026

A round of scattered showers and storms will move into the region this evening bringing strong winds and lowered vis. The highest confidence for strong storms will be for LEX and RGA. If the systems tracks more westward, SDF and HNB could get some stronger storms as well. PROB30s have been added to all sites, except BWG, due to this uncertainty, but to rely the most likely timeframe. LEX and RGA are expected to see multiple rounds of rain tonight into the early morning hours. Sites should expect some variability in wind direction with any outflow gusts. Ceilings are expected to stay VFR ,outside of possible lowered storm bases, for the remained of the TAF period.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory until 8 PM CDT this evening for KYZ023-026-061- 070>073. Flood Watch through Wednesday morning for KYZ032-033-035>037- 040>043-048-049-057. IN...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for INZ076-083-084-089. Flood Watch through Wednesday morning for INZ079.