textproduct: Louisville

KEY MESSAGES

* The hottest day of the week will be today with highs in the low to mid 90s and peak heat indices in the low 100s along and west of I- 65. A Heat Advisory has been issued.

* A cold front arrives Thursday morning with 80-90% chance of showers and a few storms possible. Fairly widespread rainfall between .5" - 1" is expected with locally higher amounts over 1.5" possible, especially along and north of I-64.

* This weekend is expected to remain active with off and on isolated to scattered showers and storms.

SHORT TERM /THROUGH THURSDAY NIGHT/

Issued at 256 AM EDT Wed Sep 9 2026

Things start off quiet today with a steadily tightening pressure gradient (20-25 mph gusts today) over the region between high pressure off the mid-Atlantic coast, and strong surface low pressure over eastern Canada. The combination of being on the northern periphery of a strong southern CONUS ridge, and the fairly impressive warm advection component on the low level SW flow will allow for a warm day with max temps in the low and mid 90s. In addition to the hot temperatures, some low and mid 70s dew points are likely to pool across our NW CWA ahead of the approaching cold front that will be trailing from the aforementioned eastern Canada low. This should yield max Heat Index values in around 105 in our far W/NW CWA where dew points are highest. Heat indices in the low 100s will be more likely as far east as the I-65 corridor. There is some concern that increasing mid to upper sky cover from upstream convection could knock temps and overall heat indices down a bit, so there is some bust potential here. Some hi-res guidance also suggests a few showers and storms could develop on remnant outflow as early as mid afternoon across our NW. Both of these factors hurt confidence, but still enough evidence to suggest some periods of ~105F are possible. Not sure we'll hit widespread 105F readings as far east as the I-65 corridor, but it will be close enough to leave current headline as is.

As we get deeper into the evening and overnight, shower and storm chances will continue to increase thanks to better forcing and moisture transport brought on by an impressive mid to upper level jet structure over the Great Lakes region. Deep layer flow will be nearly parallel to the stalling frontal boundary that will approach from the NW which will allow for some training of rounds of showers and storms later tonight through Thursday. There does continue to be a Marginal Risk of a few isolated damaging wind instances for areas along and north of the Western Kentucky and Bluegrass Parkways. In addition, WPC is carrying a Marginal Risk of Excessive Rainfall with this system. Basin average QPF is expected to be mostly in the .5" to .75" range across the area, however there has been a pretty consistent signal for localized amounts over 2-3" in spots, especially along and north of the I-64 corridor. LREF probs of over 1" continue to trend upward, and now exceed 40-50% in spots across our northern CWA. The 09/00z HREF also suggest pockets of 2-3"+ through late Thursday, which is also backed up by the 48 HR PMM data. If these values stay spread out over the 48 hour period then we should be able to handle it pretty well given how dry we have been. However, if we get most of the rain with one or two quick hitting rounds, especially later tonight into Thursday, then could see us needing a few flood advisories or warnings. Confidence and expected coverage of any flood concerns aren't high enough to warrant any headlines at the moment, but will continue to monitor trends.

The front will stall across the area through Thursday with continued rounds of W-E showers and storms moving through. The overall deep layer shear starts to weaken by Thursday, so the low end severe threat does not translate into the day on Thursday, however the threat for a few localized flood concerns will.

Will make note of a fairly impressive temp gradient across the area on Thursday thanks to the stalled frontal boundary. Looking for low 80s across southern IN, and still hanging onto the low 90s across southern KY.

LONG TERM /FRIDAY THROUGH TUESDAY/

Issued at 256 AM EDT Wed Sep 9 2026

Friday - Saturday...

The surface cold front will be stalled near the KY/TN border by Friday morning. Meanwhile, a positively tilted shortwave trough will approach and slowly move through the region. Expect lingering showers and a few storm chances on Friday ahead of this trough axis, mainly confined to central and southern KY. Overall, deep layer shear will be pretty weak by this point, so not expecting any organized updrafts. Temperatures behind the front will be notably cooler with highs on Friday in the low and mid 80s.

Looks like mainly diurnally driven showers or a storm chance continues into Saturday as another slow moving shortwave passes through the zonal flow aloft. Temps look to recover back to the 85 to 90 degree range as we enter the heart of the weekend.

Sunday - Tuesday...

The center of the upper ridge looks to retrograde slightly back into the Carolinas late weekend into early next week, helping to push the stronger belt of westerlies farther north. The increased upper ridging will come with temperatures likely holding above normal in the upper 80s and low 90s. Looks to be a somewhat "dirty" ridge with not much of a subsidence inversion to keep vertical development in check. Won't be a lot of triggering mechanisms either, outside of diurnal heating, so will only expect some isolated afternoon and evening shower or storm activity each day. Vertical shear will be weak so any storm modes would be pulse in nature.

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/

Issued at 119 PM EDT Wed Sep 9 2026

Gusty winds will continue through this afternoon with slightly higher mixing heights today. This evening a weakening, broken line of showers and storms will move into the area from the NW. HNB and SDF have the best chances for storms and briefly lower CIGs. Sites are expected to see a dry period, but a cluster of showers and a few storms will move eastward in the early morning hours. MVFR ceilings are possible with this system and lowered vis. Winds will become light and variable overnight before settling into a WSW flow tomorrow.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for KYZ023>032-061-062-070>072. IN...Heat Advisory until 8 PM EDT /7 PM CDT/ this evening for INZ076>079-083-084-089>092.