textproduct: Louisville

KEY MESSAGES

* A strong ridge of high pressure over the region will bring the hottest temperatures so far this year. The combination of heat and high humidity will yield afternoon and evening heat index values of 105+ through Friday.

* Hot and humid for the Fourth of July holiday weekend, with isolated to scattered storms possible in the afternoon and evening. Localized flash flooding and/or localized gusty winds will be possible each afternoon and evening with any slow moving storm.

SHORT TERM /THROUGH TONIGHT/

Issued at 224 PM EDT Tue Jun 30 2026

We will continue to endure the heat and oppressive dew points through the middle of the week thanks to the strong upper level ridge centered over the Ohio Valley as we go tonight into tomorrow. This afternoon, per the KY Mesonet, most locations were around 90 degrees, dew points in the mid to upper 70s with heat index values right around 100. Visible satellite image does show some scattered Cu but still expect temperatures warmer this afternoon than it was yesterday with highs into the mid 90s. When you factor in the oppressive dew point values in the mid/upper 70s it will result in heat index values around 105-110. With little change in the overall placement of the upper ridge, we can expect nearly the same kind of conditions for tomorrow. These are dangerous heat conditions with the Excessive Heat Warning remaining in place through the forecast period.

The other thing of note that can sometimes get lost in these situations are the warm overnight temperatures. Evening temperatures after sunset will fall slowly through the 80s before falling into the 70s overnight into the early morning hours. With light to calm winds, these conditions offer very little in overall relief from the heat. It is important to remember to limit prolong outdoor work and if you have to be outdoors for any prolong period of time, remember to drink plenty of water and take frequent breaks. It is also very important to check on those vulnerable like the elderly or anyone without AC, and always check your vehicle for pets or children when you reach your destination and park.

LONG TERM /THURSDAY THROUGH TUESDAY/

Issued at 224 PM EDT Tue Jun 30 2026

Thursday - Saturday...

The persistent mid/upper-level ridge that has been responsible for the hot and humid weather this week will start to slowly break down on Thursday, as well as shift off to the east. With the center of the upper high no longer overhead, we will start to erode the subsidence inversion (~800 mb cap) that's been in place. PW values will also increase into the 1.6-1.9" range per the latest LREF guidance with broad southerly flow aloft. A shortwave circling the mid/upper-level high will swing over Tennessee and south central Thursday afternoon and evening, setting up our next potential round for showers and thunderstorms. High SBCAPE (>4000 J/kg) will be in place, but with very little wind shear (< 10 kt 0-6 km shear) present the showers and storms that do develop will be pulsy in nature. The main concerns with the strongest storms that do develop would be heavy rain, frequent lightning, and strong winds. The SPC has a Day 3 Marginal Risk over far south central Kentucky for the damaging wind threat that could come from any potential microbursts. Confidence in thunderstorm coverage continues to be low, with the highest likelihood over the southern half of the CWA.

As the ridge further flattens out Friday and Saturday, the coverage of potential showers and storms increase across the area. Wind shear will still be weak, but with ample instability in place and several small shortwaves moving over the region, there will be the potential for diurnally-driven showers and storms to develop. Since most of these showers/storms Thursday-Saturday will be near-stationary, places that experience heavier downpours could have a potentially localized flooding threat. While daily maximum temperatures will very slowly begin to decrease starting Friday, mid-70s dew points will persist into the weekend, continuing the stretch of very uncomfortable conditions across the region. The Extreme Heat Warning in place has been extended out through Friday evening with 105-115 heat indices expected through the end of the week.

Sunday - Tuesday...

The mid/upper-level shifts eastward off the Atlantic coast Sunday, with a new ridge developing over the western and central CONUS through Tuesday. The mid/upper jet remains off to our north, but with multiple eastward propagating shortwaves moving over the area chances for showers and storms will continue into next week. A surface frontal boundary will slowly push southward as upper-level troughing begins to develop over the far northeastern CONUS. Though daily high temps are expected to decrease each passing day, mainly as a result of increased convective activity, the placement of the frontal boundary off to our north will allow the oppressive mid-70s dew points to persist. With the continued chance of showers and storms that could produce heavier rainfall across the long-term forecast period, we will need to continue to monitor the potential for isolated flash flooding.

AVIATION /06Z TAFS THROUGH 12Z THURSDAY/

Issued at 117 AM EDT Wed Jul 1 2026

VFR conditions are likely to continue through the current forecast period with high pressure overhead. There is some potential for patchy fog/mist to reduce VIS briefly this morning at BWG/RGA/HNB, and as this moisture mixes upwards after sunrise, can't rule out a brief period of MVFR cu around 14-16Z. Otherwise, light S/SW winds will continue through the current forecast period.

LMK WATCHES/WARNINGS/ADVISORIES

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