textproduct: Louisville

KEY MESSAGES

* Hot and humid conditions will continue through the end of the week and into the holiday weekend. Afternoon temps will climb into the lower 90s with heat indices in the 105-110 range. Extreme Heat Warning will continue through this evening. A Heat Advisory will be in effect late Friday night through Saturday evening.

* There is a risk of afternoon/evening storms this afternoon through the weekend and into next week. A few strong storms with gusty winds, heavy rainfall, and intense lightning will be possible.

* Unsettled, muggy weather continues through early-to-mid next week with modest relief from hot temperatures likely.

SHORT TERM /THROUGH TONIGHT/

Issued at 327 AM EDT Fri Jul 3 2026

It's another muggy morning across central KY and southern IN with temperatures generally ranging from the mid 70s to around 80 degrees as of 07Z. Nighttime microphysics satellite imagery shows residual upper-level cloud cover from storms Thursday afternoon across TN/Western KY, as well as river valley fog. Patchy fog, some locally dense in valleys, will continue through a few hours after sunrise before dissipating. Temperatures should only fall a few more degrees across the area through sunrise, limiting relief from the hot daytime temperatures.

Today, the 596 dm upper ridge which has been in our vicinity for much of this week will continue to dominate over the southeast US, though the center of the ridge will shift slightly east across Appalachia and toward the Carolinas. These subtle shifts in the upper level pattern will have little impact on us heating up later this morning, with temperatures rising into the low-to-mid 90s with heat indices ranging between 100-115 by this afternoon. Low-level moisture should mix up into a scattered cu field by midday, and where the cu becomes more agitated should give a hint at where convective initiation occurs this afternoon.

The somewhat decreased influence from the upper ridge will bring most if not all of the area into play for at least an isolated thunderstorm this afternoon and evening. The mid-level capping inversion will continue to weaken as 700 mb temps cool, with minimal CIN expected by the peak heating hours. On top of this, the environment will again be highly unstable this afternoon, with HREF median SBCAPE values around 4000 J/kg and high-end progs approaching 5000+ J/kg. As has been the case over the past few days, forcing is the main uncertainty, with sub-mesoscale features like differential heating boundaries and residual outflow boundaries playing a key role in where storms fire. Given this, the most likely locations where storms would develop first would be along the TN border and along/west of I-165, in closest proximity to residual outflow from Thursday evening. Once (if) storms develop, most high-res progs show N/NE propagation as the cloud-layer wind field remains weak. As is outlined by the Day 1 SPC Marginal Risk, damaging winds from collapsing wet microbursts would be the main hazard from strong storms this afternoon and evening. Steep low-level lapse rates on the order of 8-9 degrees C/km, DCAPE values exceeding 1100 J/kg, and PW values of 1.75+" all indicate favorable conditions for wet microbursts. While the elevated PW values and slow storm motions would support heavy rain/flash flooding potential, the expected pulse-y nature of convection should limit residence time, and RFC FFG values have recovered over the past few days, so anything more than very isolated flash flooding appears unlikely. Storms should begin to dissipate after sunset, with mostly dry conditions expected across the area by late evening.

Another warm and muggy night is expected tonight with low temperatures Saturday morning only expected to reach the 70s. Areas which do see rain this afternoon and evening may be able to cool off a bit more, with the increased likelihood of seeing patchy fog develop late tonight. While it is more likely that dry weather continues into Saturday morning, approaching disturbances from the NW may be able to provide enough forcing for isolated showers and a storm to develop overnight, with a few returns showing up on 00Z hi- res guidance.

LONG TERM /SATURDAY THROUGH THURSDAY/

Issued at 327 AM EDT Fri Jul 3 2026

Independence Day through Sunday Night...

Over the holiday weekend, medium-range guidance shows the ridge over the southeast US beginning to break down as shortwave troughs over the upper Midwest and the Canadian Maritimes dig into the northern extent of the high heights. The upper low over the Midwest should help to bring a front toward the Ohio Valley, especially by Sunday. Ahead of this front, PW values will remain near the 90th percentile of model climo (1.7-1.9"), and more well-defined forcing should provide better coverage of showers and storms during the afternoon and evening hours. One caveat to this would be interference from upstream MCSs which could alter the environment, though confidence in this occurring is pretty low at this lead time.

On the Fourth, more clouds/precipitation and lowering heights aloft should limit heating potential, though the current forecast still features highs in the 90-95 range with dewpoints in the mid-to-upper 70s. As a result, no changes are planned at this time to the Heat Advisory, as widespread heat indices of 100-110 are expected, and greater impacts are possible given the amount of people outdoors for celebrations. Isolated to scattered showers and storms will be possible in the afternoon and evening. While CAPE will be a little lower than on Thursday/Friday (2500-3500 J/kg per the HREF), and shear will remain weak, a few strong pulse storms producing gusty winds will again be possible.

By Sunday, the proximity of the approaching front should provide the greatest coverage of showers and storms of the next several days. Temperatures are currently expected to be a bit below persistence from Saturday, with highs in the 89-93 range Sunday afternoon. With high dewpoints still over the area, additional heat headlines may be needed, but the increased likelihood of showers and storms providing relief from the heat complicates this potential. With relatively weak shear and 2500-3500 J/kg of SBCAPE expected again on Sunday, a few strong storms will again be possible. Additionally, there may be a somewhat increased threat for flash flooding with coverage increasing and multiple rounds of showers and storms possible, though this potential still seems to be isolated.

Monday through Thursday Night...

Over the first half of next week, the upper level wave which brings the front toward the region over the weekend should begin to slide off to the northeast as ridging builds over the Plains. As a result, the front should become quasi-stationary and begin to dissipate over the lower Ohio/Tennessee Valley region Monday into Tuesday. How far south the front makes it before fizzling out will have an impact on rain chances early-to-mid next week, as lower humidity and PW values will be present behind the front. As it stands now, continued daily chances for isolated to scattered showers and storms are expected through much of next week, with greater chances the farther south you go. Temperatures should be fairly seasonable for early July, with highs in the upper 80s and low 90s and lows in the upper 60s and low 70s expected.

AVIATION /06Z TAFS THROUGH 12Z SATURDAY/

Issued at 126 AM EDT Fri Jul 3 2026

Between now and sunrise, the main source of forecast uncertainty is the potential development of patchy fog bringing MVFR/IFR VIS mainly at BWG/HNB/RGA. By mid-morning, VFR conditions are expected across all forecast sites with light and variable winds and a SCT 4-5k ft cu field expected to develop again today.

Like yesterday, there is a slight chance of TSRA, mainly at BWG, but all sites will have a 10-15% chance of a stray shower or storm this afternoon/evening. For now, we'll leave this mention out of the forecast, but PROB30 may be needed in subsequent forecasts.

LMK WATCHES/WARNINGS/ADVISORIES

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