textproduct: Louisville

KEY MESSAGES

* Waves of thunderstorms into tonight could generate severe weather, with damaging winds the primary hazard and a lower risk for large hail.

* Repeated rounds of heavy rainfall in thunderstorms through this evening could result in flash flooding. There is a level 2 of 4 (slight) risk for excessive rainfall area-wide, and a level 3 (moderate) risk for excessive rainfall across SE Indiana and north central KY.

* Additional rounds of storms are possible (20-40% chance) both tomorrow and Friday, but confidence is low on severe weather and flooding potential each day.

* 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 345 PM EDT Wed Aug 12 2026

Severe Thunderstorm Watch 577 has been issued for all southern IN counties and central KY counties until 9PM EDT/ 8PM CDT. We will continue to monitor the destabilization within the area ahead of the broken line of storms. Main hazard for storms will be damaging winds, however a brief spin up tornado cannot be ruled out. Flash flooding will also be a threat this evening and into the early morning hours.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 228 PM EDT Wed Aug 12 2026

Things have quieted down across the CWA at this hour, however any lulls in activity will be pretty short-lived as we gear up for the next round of convection later this afternoon through evening. The outflow boundary from this morning's storms was able to push westward to an Owensboro, KY to Scottsville, KY line. Areas to the east of this boundary have remained in the 70s through the morning and early afternoon, and have only recently begun to rise into the low 80s, signaling some recovery (building instability) of the airmass. To back that up, a recent ACARs sounding out of SDF shows a notable low level inversion is present. To the west of the boundary, temperatures are in the low 90s with dew points ranging in the mid to upper 70s. Could still see some heat indices in the 100 to 105 degree range this afternoon west of the boundary.

The big question for this afternoon and evening will be how much we are able to destabilize/recover the airmass ahead of developing storms upstream? The RAP depiction of SB CAPE recovery on the SPC Mesoanalysis page is quite dramatic with a quick recovery, and still has our area de-stabilizing to 4000-5000 J/KG by late afternoon. Thinking this is a little overdone given where we are currently, and like the 12/12z HREF depiction of more around 2000-2500 J/KG of ML CAPE by late afternoon. We are currently seeing quite a bit of heating where the clouds have cleared, however this window may also be pretty shortlived as convective debris from the upstream system will soon be overspreading the area.

Some of the latest runs of the hi-res data do suggest that a developing convective complex will make it into our area, however they may be a little overdone on intensity if we aren't able to fully recover. In contrast, if we do quickly destabilize then we will be in play for another evening of damaging wind threats, especially if a good cold pool is able to get established upstream ahead of time. SPC did expand the Slight Risk over our entire area, which suggests the more unstable solution, and recent collaboration with them has suggested that a Severe Thunderstorm Watch is possible, but we are going to wait and see how we destabilize. Timing still looks pretty good for storm arrival around 4 or 5 PM EDT across our northern CWA, pushing south through the CWA into the evening, and exiting our SE around 10 PM EDT or so. We'll also have to watch for any heavy rainfall to develop into a Flash Flooding concern, particularly across areas that saw a lot of rain last night and this morning. Essentially where WPC has drawn the Moderate Risk.

After the evening wave pushes through we do expect a brief lull in activity. However we may see a similar scenario set up through the overnight to what occurred last night. The remnant convectively reinforced outflow is expected to set up in a more W-E fashion somewhere around the I-64 corridor. Here, we could get redevelopment of showers and storms overnight as the boundary stalls roughly parallel to the upper flow and there is at least some modest low level jet contribution to moisture transport. Much like last night, the 12/12z HREF suggests some very impressive rainfall totals from the max ensemble member, and has some support from the PMM data as well. In addition, the 12/12z HRRR also pegged a bullseye of 5+" across southwest IN in a localized area. Forecast models this afternoon continue to suggest some training of storms in that area through the overnight, so felt it prudent to extend the Flood Watch across southern Indiana through 12z Thursday morning to account for this threat. Not a slam dunk, but also could have some localized high end flooding impacts like we saw last night across east central IN. Same setup, just a different orientation.

A lot of what happens this evening and tonight could have a bearing on what happens going into Tuesday. Wherever the remnant boundary sets up will be the focus for additional shower and storm activity through the afternoon and evening. The NW flow pattern aloft will continue on the NE periphery of the upper ridge so this should keep most of the convective activity across the northern and eastern portions of the CWA. Additional damaging wind threats may develop along with a lingering Flood threat, or enhanced flood threat if it is still ongoing from any overnight activity. Our SW CWA would be most likely to get in on a Heat Advisory tomorrow, but will again take a wait and see approach give convective activity and the potential to bust a temp forecast.

LONG TERM /FRIDAY THROUGH WEDNESDAY/

Issued at 228 PM EDT Wed Aug 12 2026

*** Friday through Mid Next Week ***

A weak shortwave trough will bring chances for some rain showers on Friday, however confidence is low in timing or intensity at this time. An upper level ridge will begin to build over the region at the end of the week into the weekend. This will bring in a warmer and slightly drier air mass to the Ohio Valley. Maximum temperatures for the weekend are expected to be in the mid to upper 90s, with heat indices potentially reaching triple digits.

Moving into early next week, a frontal boundary is forecasted to move through the area from the NW. This will bring rain chances back into the forecast and possibly a brief relief in temperatures. However, this is not expected to last long as another warm airmass will move back into for the middle of the week.

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/

Issued at 123 PM EDT Wed Aug 12 2026

Additional rounds of showers and storms will move through the area this evening/tonight into tomorrow. All sites have PROB30 groups for a broken line of storms this evening, and scattered showers/storms early tomorrow. Winds will be variable through the night with storms and developing outflow boundaries. Tomorrow afternoon winds should be primarily light and from the WSW. Cloud ceilings are expected to stay VFR, outside of MVFR storm cloud bases.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Flood Watch through Thursday morning for KYZ025-029>043- 047>049-055>057-066-067. IN...Flood Watch through Thursday morning for INZ076>079-083-084- 089>092.