textproduct: Louisville

KEY MESSAGES

* Heat Advisory continues into this afternoon * Temperatures will again be hot today, with afternoon highs just a couple of degrees lower than Friday

* A weak cold front will increase the chance of isolated to scattered showers and storms this afternoon and evening, ending our stretch of hot conditions across the region by the end of the weekend

UPDATE

Issued at 334 AM EDT Sat Sep 5 2026

Atmosphere a little more frisky over our region earlly this morning...with satellite and radar showing some modestly growing cells along an axis from Washington County IN to Louisville to southern Bullitt County KY. One or two of the high-res models did pick up on this activity, so leaned a bit more heavily on them for the near term. Complex well to our north and northeast seems to be staying up in that region for now. Seeing a little more southward push over far NE IN, but not sure that will continue on that trajectory all the way to our Bluegrass zones. Likely will maintain the Heat Advisory as is.

SHORT TERM /THROUGH TONIGHT/

Issued at 214 AM EDT Sat Sep 5 2026

Continuing to watch showers and storms over southern MI and a recent line developing in western OH this hour. GOES Sounder data is keeping the peak precipitable water axis over northern IN/southern MI into NW Ohio, so expect these storms will continue trending east southeastward. There is a small pool of higher CAPE over eastern IN and western OH, per that sounder data. Evening forecaster mentioned we could see some development along the western edge of any storms moving into western OH. A few more of the late running 00Z hi-res models are showing a line of showers/storms into our SE IN/Northern KY counties by morning, so see no reason to lower pops there.

What those storms do for our area could greatly impact the ongoing Heat Advisory. Running a blend of NBM data with several of those hi- res models gives high temperatures in the low-mid 90s range this afternoon in our northest zones, with heat indices in the 99-104 range. Points along and west of I-65 would peak in the mid to upper 90s with heat indices generally around 105. In addition, outflows left behind by the potential morning wave of storms should serve as focus for new development in the afternoon, in addition to the backdoor cold front dropping down from the north and northeast. Some of these could linger into the evening hours as well.

As for the strength of these storms...feel the morning wave should mostly be elevated. Cannot rule out some brief gusty winds and will be able to monitor upstream obs over IN/OH to see if any winds can get down into our SE IN/northern KY areas. For the afternoon wave, we should have several pockets of higher instability and DCAPE to warrant damaging wind potential given in latest SPC Outlook. Best chance for this potential runs from roughly 3-10 PM this afternoon/evening. Again, wind likely is the biggest threat here, with nearly unidirectional afternoon shear profiles, and mostly a northwesterly direction at that. Machine learning guidance favors this time frame as well. As for locations, pretty much east of a Corydon to Etown to Campbellsville line has the better chances.

As for the Heat Advisory in place, will be watching those storms up over southern MI/northern IN to see if they will get into our region by daybreak. Will wait a few more hours before making any decisions to trim that up.

LONG TERM /SUNDAY THROUGH FRIDAY/

Issued at 214 AM EDT Sat Sep 5 2026

Sunday into at least Monday, most of the area should see northerly to northeasterly winds, bringing a "cool"down to more normal temperatures for early September. By Tuesday the surface high bringing that cool down shifts into the NE US and we see a quick southerly return flow for midweek. Ridging builds in aloft as well, so temperatures will rebound just as quickly above normal.

Our next cool front could move into the region Wednesday night into Thursday time frame. Long Range Ensemble Forecast (LREF) has quite a bit of spread for temperatures and rain chances in that period and continuing to close out the work week.

AVIATION /06Z TAFS THROUGH 12Z SUNDAY/

Issued at 112 AM EDT Sat Sep 5 2026

Still looking at a potential for storms currently over southern MI to move southeast and backbuild over IN. These cells may survive into KLEX by mid morning, so have added a short prob30 group there. More likely by mid afternoon we will see scattered storms develop across the region, as a cold front approaches. Storm coverage should diminish quickly with sunset and winds will become more northerly this evening. Model profiles do show some stratus development early Sunday morning along the I-64 corridor, so have shown that in this set of TAFs.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for KYZ023>043-045>049-053>057-061>067-070>078-081-082. IN...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for INZ076>079-083-084-089>092.