textproduct: Louisville

KEY MESSAGES

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

* Milder weather will gradually overspread the area this week, with highs likely (60-80% chance) in the 70s north of an Owensboro to Berea line by Tuesday, and area-wide by Wednesday.

* While an isolated storm can't be ruled out this afternoon, the best chances (30-50%) will be tonight into Monday morning near and north of I-64, and again Monday afternoon and evening east of the I-75 corridor. Dry weather is forecast to rest of the week.

SHORT TERM /THROUGH MONDAY/

Issued at 138 AM EDT Sun Sep 20 2026

*** HOT AGAIN, FEW PM STORMS TODAY ***

Beneath a ridge of high pressure, the airmass over central Kentucky and southern Indiana remains unseasonably warm and still somewhat humid. At 130am Sunday morning, temperatures were in the low to mid 70s and dewpoints were anywhere from the mid 60s across western Kentucky to low 70s over the Bluegrass where gentle southerly flow was resulting in moisture pooling against a southward-sinking outflow boundary. It remains to be seen how far south this feature will settle early this morning, but wherever that boundary "lands," potential will exist for at least isolated (20-30% coverage) afternoon showers and storms. The NAMNest, which, of the convective allowing models (CAMs), looks most like current radar - capturing the ongoing storms over southern Ohio and West Virginia - suggests that outflow will spark storms mainly over areas near and east of the I-75 corridor after around 3pm EDT. However, this is just one of a myriad of solutions given by HREF membership, and it is very possible that at the current time it is simply "right for the wrong reason," and therefore may not necessarily have the best forecast. I ended up blending the National Blend of Models (NBM), HREF, and NAMNest for PoPs this afternoon and evening to try and capture the uncertainty while hedging slightly to the current best performing model; this results in 15-20% chances for precipitation over eastern portions of the county warning area (CWA) this afternoon and evening. Elsewhere, it'll be another hot - albeit slightly less humid - day with afternoon highs solidly in the 90s. It'll be a struggle to reach traditional Heat Advisory criteria (heat indices 105+) due to lower dewpoints (forecast to fall into the mid 60s) during the afternoon, but opted to continue the Advisory across areas near and west of a roughly French Lick to E-town to Edmonton line where HeatRisk remains moderate to high and wetbulb globe temperatures are forecast to once again reach the mid-upper 80s.

*** FEW STORMS MAINLY NEAR/NORTH OF I-64 TONIGHT ***

This evening into tonight, a pair of shortwave troughs will pass across Indiana - bringing increased chances for showers and storms across areas mainly near and north of the I-64 corridor. Fortunately by then, diurnally-driven instability should be waning, but increased shear (20-30kt in the 0-6km layer) could result in a marginally severe storm with locally damaging winds the primary concern and a lesser risk for hail. SPC maintains a level 1 of 5 (marginal) risk across our northern counties to account for this potential, which will be highest with the evening round if we get anything (the chance is 20-30%); storms may stay just north of the CWA until early Monday morning with the second shortwave.

*** MILDER NORTH, STILL HOT WITH STORM CHANCES SOUTH MONDAY ***

A front is slated to sink southward across our area on Monday, perhaps (40-60%) triggering additional storms over southern Kentucky and the Bluegrass, however, at least according to the 20.00z CAMs, most of the area is now looking to stay dry with that frontal passage. This front will drive a gradient in temperatures across the forecast area, with the heat likely lingering another day over southern Kentucky but milder conditions overspreading the I-64 corridor and points north where highs may struggle to reach 80 in spots.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/

Issued at 138 AM EDT Sun Sep 20 2026

*** TURNING GRADUALLY MILDER MIDWEEK ***

As gentle northerly flow continues, the local area will feel progressively drier and less warm Monday night into Tuesday, by which time dewpoints should dip into the 50s across northern portions of the area. Parts of southern Kentucky may still warm into the 80s Tuesday afternoon, but most locations will see highs in the 70s and overnight lows in the upper 50s to low 60s. Wednesday and onward, the continual northerly flow should (NBM chances are roughly 60-80%) maintain highs in the 70s and lows in the 50s each day area wide - which, though much cooler than what we've become accustomed to as of late, is near normal for late September.

AVIATION /18Z TAFS THROUGH 00Z TUESDAY/

Issued at 138 PM EDT Sun Sep 20 2026

VFR will prevail for much of this TAF period, although some notable weather impacts are possible. Surface winds are steady out of the SSW this afternoon, with perhaps a few gusts up around 15 to 20 mph. Winds will slacken around sunset, and will go light and variable as a weak frontal boundary sinks southward through the I-64 corridor. Isolated showers and storms are possible overnight with this frontal passage, however coverage and confidence are quite low. Surface winds will eventually take a light N or NE component through tomorrow along with some lower clouds possibly working into the northern TAF sites. There are some probs for IFR conditions at HNB, but for now will hint at MVFR as the lowest ceilings have trended slower and may end up just north of the area.

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.