textproduct: Louisville

KEY MESSAGES

* Mostly dry and warmer today. A few light showers possible later this morning through the daylight hours. No T-storms expected.

* The hottest day of the week will be Wednesday with highs in the low to mid 90s and peak heat indices in the low 100s along and west of I-65.

* A cold front arrives Thursday morning with 80-90% chance of showers and a few storms possible. Fairly widespread rainfall between .25" - .75" is expected with locally higher amounts over 1" possible, especially along and north of I-64.

SHORT TERM /THROUGH TONIGHT/

Issued at 254 AM EDT Tue Sep 8 2026

Strong upper ridging continues to dominate the southern CONUS today, with plenty of influence extending through the Ohio River Valley. Surface high pressure will be centering over the mid Atlantic, which will allow a steady SSW wind to develop this afternoon. Given the upper ridge and a steady warm advection component, temps are expected to be warmer than yesterday as they climb back to the upper 80s and lower 90s. Fairly rich low level moisture could contribute to a bit more cloud cover than anticipated this afternoon, and that would be the only limiting factor to realizing these above average temps.

We should be mostly dry under this pattern, however we'll still be dealing with the inverted surface trough lingering from yesterday. This feature will continue to contribute to an axis of ~70F Tds stretching SW-NE through the area which will allow for a roughly ~500 J/KG instability axis along with some weak but persistent surface convergence. This will likely be enough to trigger some isolated showers later this morning into the afternoon, however forecast soundings show a notable H7 inversion, which is supported by the upper ridge pattern. Given that feature, any vertical development will only make it a few thousand feet. As a result, will only carry the shower mention without any thunder forecast. Most will stay dry with the most likely area for a few showers across our southern or SW CWA. Any showers will die off with the loss of heating tonight. Lows will find their way down to the upper 60s and low 70s.

LONG TERM /WEDNESDAY THROUGH MONDAY/

Issued at 254 AM EDT Tue Sep 8 2026

Wednesday - Thursday Night...

Elongated upper ridging will be in control across the southern half of the CONUS on Wednesday, with a belt of zonal westerlies controlling the northern half of the CONUS. At the surface, a notably strong pressure gradient will exist across the Ohio River Valley between surface high pressure anchored off the mid-Atlantic coast and a strong surface low over eastern Canada. This will give us a steady to occasionally gusty SW flow with peak gusts likely in the 20-25 mph range through the afternoon. This will be the hottest day of the period with temps warming into the low and mid 90s across the area. Dew points are also expected to "pool" across our NW CWA a bit ahead of the approaching cold front, but this will also be the area closes to upstream convection and afternoon cloud cover could play a limiting role. Regardless, max heat index values will be into the triple digits along and west of I-65 at some point Wednesday afternoon. For now, looks like we'll stay just short of any headline criteria for most of the area, but will continue to monitor T/Td trends as it will be close in our NW CWA.

As we move into later Wednesday evening through Thursday, we'll deal with fairly widespread convective activity along a cold front trailing from the aforementioned eastern Canada surface low. Fairly impressive late summer speed shear profile (25-35 knots) will be in place across our northern CWA thanks to strong mid to upper level jetting, and a decent low level jet response. If we do get a stronger updraft, then this would be sufficient for some organization, and perhaps an isolated strong to severe threat. Main problem is that instability looks pretty meager later Wednesday evening into Wednesday night. By the time modest instability develops on Thursday, the overall shear profile is a bit weaker across central and southern KY. Can't rule out a few strong to severe storms later Wednesday evening into Thursday, but overall not real impressed with the overall scenario, and SPC Marginal Risk seems appropriate.

Will also have to watch for the potential for a few swaths of heavier rain through Thursday night, even if it might be welcome in most locations. The overall orientation of the deep layer shear profile will be roughly parallel to the surface frontal boundary, and this could allow for some training/repeated rounds of showers or storms. 07/12z LREF data did increase probabilities of over 1" of rain from 10-15% to 20-40% along and north of the I-64 corridor. This is a notable increase, and have also noted that a few of the deterministic models show some isolated swaths of 2-3". These values still aren't overly concerning given how dry we've been, but nevertheless something to monitor for trends.

Friday - Monday...

The late week into the weekend time frame now looks a lot more active than it did 24 hours ago as the overall frontal progression has slowed, and now lingers across KY into the weekend. In addition, a slow moving shortwave on the southern end of the stronger belt of westerlies looks to meander out of the southern Plains into the Tennessee Valley, and could be a spark for additional diurnally driven showers and storms through the weekend mainly across central and southern KY. Will keep lingering iso-sct chance pops in the forecast through the weekend to account for this.

After a brief cool down with temps in the low and mid 80s behind the front on Friday, max T's should quickly recover to the upper 80s to around 90 through the weekend.

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 633 AM EDT Tue Sep 8 2026

VFR is expected to prevail through this forecast cycle, although a couple of minor weather impacts worth noting. Expect Sct-Bkn clouds around 4-5 K feet to increase through the morning as a weak surface boundary focuses low level moisture over the area. Light SE winds early this morning will give way to more steady SSW winds later morning into the afternoon. A few gusts up between 15 and 20 mph may be possible. In addition, a few isolated showers could develop from late morning into the afternoon, although confidence and coverage are too low to include mention. Ceilings gradually rise and scatter out through late afternoon and early evening, however VFR conditions continue to prevail.

LMK WATCHES/WARNINGS/ADVISORIES

KY...None. IN...None.