textproduct: Louisville

KEY MESSAGES

* Severe thunderstorms are likely from midday Tuesday through Tuesday evening, with all severe hazards possible. Damaging straight-line winds are the main hazard, but a few tornadoes and large hail will be possible. Localized heavy rainfall may lead to flash flooding, especially east of I-65.

* Calm weather moves in with cooler than average highs for Wednesday through Friday this week.

SHORT TERM /THROUGH THIS AFTERNOON/

Issued at 404 AM EDT Tue Jul 21 2026

Today, an upper ridge will begin to amplify northward into Canada as an upper trough begins to drop south through the Upper Ohio Valley. The upper trough will push a surface low east across Ontario and into Quebec. The system's cold front will drag south through the Great Lakes and westward towards the Ozarks under northwest flow directed towards the Ohio Valley. Ahead of the front, across the CWA, precipitable water values sit between 1.5 to 2", but just ahead of the front values will jump as high as 2.4", mainly west of Interstate 65. This moisture as well as strong WAA will be driven by 10-15 mph southwest winds with gust to 20-25 mph. This will push temperatures into the mid 80s to low 90s as dew points climb through the 70s to near 80, again west of Interstate 65. It's in this area that heat indices have the best chance to reach 105. The heat advisory extends farther east to make a pretty picture, but there is a chance that remaining cloud cover from upstream convection over Missouri and Illinois and our own convection could impact overall warm temperatures and high humidities, especially in areas farther north and east.

The severe threat continues to evolve. Yesterday it looked like we would have two distinct lines of convection with one arriving during the late morning and one during the afternoon/evening just ahead of the cold front. Now, it's looking more likely that there will be one main line that could be broken or have supercells embedded or pass through around the main line. All hazards remain with straight-line wind being the main threat. MLCAPE levels remain high between 2,000 to just over 3,000 J/kg. Deep layer shear around 40 knots with areas with backed surface winds, adding to a tornado threat. Model soundings still show some areas with fairly stable low level lapse rates or even elevated storms. This may be a little protection, but would still expected parts of the area to see severe weather today. Very high MUCAPE values in rotating updrafts could lead to large hail.

It still appears, that thunderstorms will begin to move into parts of southern Indiana around 16z with storms reaching Louisville around 19-20z and Lexington around 20-21z as the surging part of the line is expect to dive through the Bluegrass region a little quicker. Areas farther west and south toward Bowling Green may see storms anywhere from 21z to 02z Wednesday as the line drops a little slower to the south.

There is also a flash flooding concern with the extremely high precipitable water values. These values are high for any time of year. Believe in general these storms will keep moving and reducing their flooding risk, but with the expected heavy rainfall rates, any area that see multiple storms could be a serious risk of flooding. Because of this, we are issuing a flood watch along with our neighbors.

LONG TERM /TONIGHT THROUGH MONDAY/

Issued at 404 AM EDT Tue Jul 21 2026

Early tonight, most of the activity will be out of central Kentucky. Winds will begin to ease as they veer towards the north. Skies will try to clear and this could lead to areas of fog from earlier moisture as temperatures fall into the mid 60s to low 70s.

Behind the front, surface high pressure will bring CAA and cooler temperatures with highs in the upper 70s to mid 80s through Friday before the high passes to the east and WAA returns, brining mid 80s to low 90s back for the weekend. Dry weather is expect through the end of the workweek with low-end rain chances returning around the weekend into early next week as little surface systems ride in on northwest flow.

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 656 AM EDT Tue Jul 21 2026

Convective activity over Missouri and southern Illinois is generating a layer of high level cloud debris that is blowing over southern Indiana and central Kentucky. A cold front is expected to bring a line of possibly severe thunderstorms to area TAF sites. Sites should expect strong gusty winds and reduced visibilities from heavy downpours. Hail is also a concern in these storms.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory from 10 AM this morning to 7 PM CDT this evening for KYZ023-024-026-027-061>063-070>076-081. Flood Watch from 1 PM EDT this afternoon through this evening for KYZ033. Flood Watch from 1 PM EDT /noon CDT/ this afternoon through late tonight for KYZ034>043-045>049-053>057-063>067- 073>078-081-082. IN...Heat Advisory from 11 AM EDT /10 AM CDT/ this morning to 8 PM EDT /7 PM CDT/ this evening for INZ083-089.