textproduct: Louisville

KEY MESSAGES

* Unseasonably hot weather will continue area-wide this afternoon and over southern Kentucky tomorrow, with afternoon heat indices near 100 degrees.

* While an isolated storm can't be ruled out this afternoon, the best chances (30-40%) will be tonight into Monday morning near and north of I-64, and again Monday afternoon and evening along and south of the Western Kentucky and Bluegrass Parkways. Dry weather is forecast to rest of the week.

* Milder weather will gradually overspread the area this week, with highs in the 70s north of an Owensboro to Berea line by Tuesday, and area-wide by Wednesday. Dry weather and pleasant temps look to hang around through the weekend.

SHORT TERM /THROUGH MONDAY/

Issued at 253 PM EDT Sun Sep 20 2026

Things are mostly quiet across the CWA at this hour, however an isolated shower or storm is possible through the afternoon and evening. This threat is mainly for areas east of I-65 where some moderate instability has developed, and current visible satellite imagery shows some scattered agitated cu. A gravity wave did pass SE through the CWA earlier this morning into the early afternoon, however it was becoming less defined the farther SE it got, and not sure how much of a triggering role, if at all, it will play. Other than that, hot conditions continue today with temperatures already in the low to mid 90s. SDF has good chance to tie the record of 96 degrees, if not break it, however some upper clouds have begun to stream in and that could be a limiting factor. Thanks to some drier dew points, heat indices are mostly going to peak in the 95 to 100 degree range, although some values up near 105F are still possible in the Heat Advisory. No changes planned to that.

As we move into late evening and tonight, focus shifts to a weak surface boundary sinking southward into the Ohio River Valley region. This feature may be able to trigger isolated to widely scattered showers or a few storms as it does so. Modest instability looks to remain overnight (ML CAPE values 500-1000 J/KG), and this combined with deep layer shear in the 25-35 knot range should be enough for perhaps a few stronger storms capable of gusty winds. SPC Day 1 Marginal Risk covers the low but non-zero probs for a damaging wind event along and north of I-64 through the overnight.

As we move into Monday, the surface boundary will work into southern KY while surface high pressure starts to build into our north in the post-frontal wake. Expecting most of the convective activity will be mainly diurnally driven and across the southern half of the CWA closer to the front. Here there is pretty high confidence in 1500- 2500 J/KG of ML CAPE developing along with sufficient deep layer shear for some organized updrafts. Another Marginal Risk is in place for areas along and southeast of a Bowling Green to Lexington line where an isolated damaging wind gust can't be ruled out.

Temperatures will start to cool across our northern CWA with highs in the low and mid 80s across southern IN and northern KY. Across southern KY, we'll still hold onto hot and humid conditions with peak temps in the low 90s.

The upper ridge over the southern CONUS continues to break down on Tuesday, allowing the surface front to sink south of KY. A shortwave embedded in the zonal flow across the Ohio River Valley will approach and may be a catalyst for additional shower and storm coverage across our SE CWA. Will keep pops there, but the good news is that temps will be notably lower. Highs in the mid to upper 70s are expected across southern IN and northern KY, while southern KY looks to top out in the low 80s.

LONG TERM /MONDAY NIGHT THROUGH SUNDAY/

Issued at 253 PM EDT Sun Sep 20 2026

Wednesday - Sunday...

The shortwave trough axis will be pushing east of the area by Wednesday morning, and will close off over the mid Atlantic states as we move into late week. Meanwhile, an H5 Omega Block will be building from the western Gulf up through the western Great Lakes, including our area. At the surface, an expansive area of high pressure over eastern Canada will extend influence into our region. The end result of this pattern will be a period of dry weather from mid to late week through the weekend. May need to linger a few small rain chances along the I-75 corridor Wednesday morning as the trough axis pushes east, otherwise will be dry elsewhere.

In addition to the dry conditions, temperatures will be notably cooler and more comfortable, albeit still around normal for this time of year. Looking for highs mostly in the mid to upper 70s each day Wed-Sat, with temps more in the lower 70s for the Bluegrass region. By Sunday, some low 80s will likely return. Dew points will sink into the upper 50s and low 60s through mid week, and then down more into the low and mid 50s for the weekend. This will allow for some crisp mornings with lows in the low to mid 50s for the weekend.

AVIATION /00Z TAFS THROUGH 06Z TUESDAY/

Issued at 717 PM EDT Sun Sep 20 2026

VFR conditions are expected to continue through much of the TAF period. As a surface low moves over the area tonight along with a frontal boundary, winds will become variable overnight. By the end of the TAF period, winds will primarily be out of the NE for all sites. A lower cloud deck will attempt to push into the area from the north tomorrow morning. HNB will have the best chance of seeing MVFR ceilings with some IFR secondary bases. Scattered to isolated showers and storms will remain in the forecast as this boundary moves through the area. Lowered vis will be possible with any heavy rainfall that develops.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for KYZ023>028-053-061>063-070>076. IN...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for INZ083-089.