textproduct: Louisville

KEY MESSAGES

* Temperatures will begin to trend downward this weekend, though highs are still expected in the low 90s today. Afternoon heat indices between 98-105 may lead to some heat-related impacts at Independence Day events. A Heat Advisory remains in effect through this evening.

* Scattered showers and storms are expected during the afternoon and evening today and Sunday. A few strong storms with gusty winds, heavy rain, and lightning are possible.

* More seasonable temperatures and intermittent rain chances are expected for the upcoming week.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 343 AM EDT Sat Jul 4 2026

===== Today and Tonight =====

Quiet weather is present across central KY and southern IN as of 07Z, with nighttime microphysics satellite imagery showing a mixture of mid- and high-level clouds left over from convection Friday afternoon and evening. A welcome side effect of the storms yesterday evening was a strong cold pool which spread across the region, bringing milder and less humid air to the surface. At this hour, temperatures are generally in the upper 60s and low 70s across the area, with dewpoints in the mid-to-upper 60s. Over the next few hours, mostly dry conditions are expected across the area. While earlier hi-res runs like the 00Z HRRR showed showers and storms re- developing, this is somewhat doubtful given weak forcing and a fairly deep stable layer near the sfc, though we'll have to monitor upstream convection to our NW. Additionally, fog should be more limited this morning thanks to lower Tds; however, patchy fog will be possible in areas which received rain Friday afternoon and evening.

Today, the upper-level ridge over the southeast US will begin to weaken and flatten out as troughing begins to sink out of the upper Midwest. Lower heights and thicknesses, as well as a cooler start this morning should lead to high temperatures a couple degrees below persistence this afternoon, with the current forecast ranging from 90-94 across the area. While dewpoints should recover later this morning, the slightly cooler temperatures combined with lower dewpoints should lead to lower heat indices generally ranging from 98-105 this afternoon. Given the amount of outdoor events today, the heat advisory still provides good messaging, so no plans to make changes to headlines at this time.

The chance for showers and storms later today carries quite a bit of uncertainty, as there is some suggestion in recent hi-res guidance that the outflow-modified environment will delay or preclude convective initiation across much of the area. 00Z HREF guidance does show a relative minimum in SBCAPE across central KY and southern IN today, though this does begin to fill in from west to east later this afternoon. A sfc cold front dropping out of the upper Midwest later today should bring a few convective complexes toward the region by this evening, though it is uncertain whether they will reach our area before the end of peak heating/instability. As has been the case over the past several days, shear will be weak, so it will either be slow-moving pulse-type convection or cold pool driven complexes which will impact the area this afternoon and evening. Gusty winds would be the main hazard with storms, while localized flash flooding would also be possible in slow-moving storms.

While convective activity will likely diminish once again after sunset, better forcing from upstream convective complexes as well as the weak upstream trough/sfc front could lead to isolated to scattered showers and storms overnight tonight. Otherwise, dry weather with temperatures falling into the low-to-mid 70s is expected overnight into Sunday morning.

===== Sunday and Sunday Night =====

During the day on Sunday, mid- and upper-level heights will continue to decrease across the Ohio Valley with the sfc front gradually pushing toward the area. With PW values around 1.8" and CAPE ranging from 2000-3000 J/kg during peak heating combining with modest forcing from the upper trough/sfc front, would expect scattered showers and storms to develop across the area once convective temperatures are reached in the late morning and afternoon. At this time, the area is only in a general thunderstorm risk from SPC, and ingredients are somewhat less favorable than over the past few days. While there will be a bit more shear (maybe 15-20 kt), a "skinnier" CAPE profile with less mid-level dry air and less steep low-level lapse rates will suppress (but not eliminate) the wet microburst potential. Once again, can't rule out a strong storm or two as well as localized flash flooding, but the overall threat appears to be low at this time.

Given the coverage of showers and storms and the weakening upper ridge, Sunday should see another small step down in temperatures, with highs currently forecast to range from 88-92. With peak heat index values across the area only approaching 100 degrees Sunday afternoon, have no plans to extend the heat headlines at this time, though we will continue to monitor trends in short range guidance.

Sunday night, the sfc cold front should begin to push through the region, though it is uncertain if it will make it through the area by Monday morning. Convective coverage should decrease once again after sunset, with temperatures settling into the low-to-mid 70s Monday morning.

LONG TERM /MONDAY THROUGH FRIDAY/

Issued at 343 AM EDT Sat Jul 4 2026

===== Monday through Wednesday Night =====

At the beginning of the week, baggy upper level troughing will extend from the mid-Miss. Valley up into the Great Lakes, with an associated sfc cold front either overhead or just south of the area Monday morning. For the first few days of the week, this upper trough is expected to slide off to the east without much southward progression as ridging begins to develop across the Rockies and Plains. This upper level pattern evolution should cause the sfc front to slow and eventually stall out, and the positioning of the front will have considerable impacts on rain chances Monday through Wednesday. Along the front and points south, PW values around the 80th-90th percentile of climo (1.75-1.85") suggest a continued moist and unstable environment, with a less moist and unstable environment to the north of the front.

Medium-range guidance is struggling with where the front eventually stalls out early in the week. Evidence of this can be seen via large spread in forecast PW values across the lower Ohio Valley Tuesday into Wednesday. If the drier air pushes into the area, daytime shower/storm chances will be more isolated, while scattered to numerous coverage will be possible if the front and higher moisture hangs farther to the north. In general, the best coverage of afternoon showers and storms during the first half of the week should be on Monday, with a north-south gradient in rain chances (lower north) expected Tuesday into Wednesday. With relatively weak deep-layer shear (10-15 kt) and seasonable amounts of instability expected, any storms which do develop should mainly be of the typical summertime variety.

There is better confidence in the temperature forecast over the first half of the week, with fairly seasonable values currently expected bringing some relief from the intense heat. Highs should range from the mid 80s to around 90 with morning lows in the upper 60s and low 70s.

===== Thursday through Friday Night =====

By the middle of the upcoming week, the ridge which builds over the Rockies and Plains will try to spread east into the Ohio Valley. However, at the same time, a nudge from a Pacific jet extension should help bring another upper trough from the upper Midwest down toward the Ohio Valley Thursday into Friday. Ahead of this disturbance, increasing moisture should support increasing chances for showers and thunderstorms, though exactly how quickly this system arrives has a bit of ensemble spread associated with it. The current forecast calls for increasing rain chances Thursday into early next weekend, with temperatures remaining fairly steady. Extended range AI/ML severe convection guidance doesn't show a concerning signal at this time; however, the usefulness of this product with summertime weakly-forced convection is doubtful.

AVIATION /12Z TAFS THROUGH 18Z SUNDAY/

Issued at 656 AM EDT Sat Jul 4 2026

VFR conditions and light S/SW winds are expected for much of the daytime hours today. SHRA/TS which has developed near RGA may continue for a few hours, but is expected to push off to the east by late morning. Recent trends in model guidance keeps area forecast sites free of showers and storms for most of the day today, with a wave of precipitation potentially pushing into the region from the west around 0Z tonight. Due to low confidence in TSRA timing and coverage, have largely removed mention from the current forecast, though short-fuse amendments may be needed later today as satellite and radar trends build confidence. Otherwise tonight, light or calm winds should continue with VFR conditions expected. Some patchy fog cannot be ruled out early Sunday morning.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for KYZ023>043-045>049-053>057-061>067-070>078-081-082. IN...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for INZ076>079-083-084-089>092.