textproduct: Louisville

KEY MESSAGES

* Hot and humid conditions into the weekend with highs in the low/mid 90s with heat index values up to 108 degrees both days. Heat Advisory is in effect this weekend for a large portion of southern IN, central and southern KY.

* Isolated thunderstorm chances this afternoon and evening (20-30% chance). There is a low end chance of any storms being strong to severe with gusty winds the main threat.

* Additional storms are possible (20-30% chance) across areas mainly east of a Salem, Indiana to Richmond, Kentucky line tomorrow afternoon and evening. Any storms that form could be severe with damaging winds and large hail.

SHORT TERM /THROUGH TONIGHT/

Issued at 325 PM EDT Fri Aug 14 2026

The bulk of the rain and thunderstorm activity today has been mainly across central Indiana along a stalled frontal boundary. But we've seen a few isolated showers and thunderstorms try to develop along a lingering outflow boundary that is currently cutting across the CWA along and near both the Western Kentucky and Bluegrass Parkways. There is also a second outflow boundary closer to the KY/TN border. Both of these boundaries can be seen on the visible satellite imagery. While SPC has the area under a marginal risk for severe weather (level 1 of 5) the dynamics are marginal at best. Wind shear is to the north along the boundary and the cloud cover to the north has created a west to east instability gradient across the county warning area (CWA). Isolated convection is expected through the remainder of the afternoon and evening which is in general agreement with most of the CAMs and short range model guidance.

The other story today has been the heat and humidity as a Heat Advisory will continue through the afternoon and early evening before being allowed to expire around 9pm EDT/8pm CDT. Many locations in the Heat Advisory have had heat index values above 105 degrees with areas to the north within the cloud cover in the low/mid 90s for heat indices.

As we go overnight, any convection that develops in the evening will be diminishing and we should mostly clear conditions. It will remain warm and muggy with lows in the low/mid 70s.

LONG TERM /SATURDAY THROUGH FRIDAY/

Issued at 325 PM EDT Fri Aug 14 2026

***** HEAT AND HUMIDITY THROUGH THE WEEKEND *****

The main weather impact for the weekend will be temperatures warming into the mid/upper 90s as upper level ridging expands northward over the Ohio Valley into the Great Lakes and the stalled frontal boundary currently over central IN lifts northward towards northern IN and southern MI tomorrow. Because of this, a second Heat Advisory was issued for Saturday morning into Sunday evening for most of the CWA with heat index values up 108 degrees when you factor in dewpoint values into the mid/upper 70s both Saturday and Sunday.

The main limiting factor to the heat, especially across the Bluegrass and our far eastern CWA will be cloud cover and the potential for showers and thunderstorms especially on Saturday. Models continue to highlight an MCS over IA and northern IL at the start of the day tomorrow. This activity is then forecast to work along the boundary and dive southward out of eastern IN towards Cincinnati in the afternoon extending into the far northeastern portion of our CWA. The other thing we would need to watch will be any outflow boundaries that form and work southward into southern IN. These boundaries could be enough lift to fire off some limited convection. SPC does have portions of our CWA, Harrison and Nicholas counties under a Slight Risk or level 2 out of 5 for severe weather as there will be a little better bulk shear for possible gusty winds and hail with a Marginal risk extending back to the west from Louisville down to Somerset. Overall confidence in severe and even storm threat remains low.

The next potential threat for storms will come with an approaching boundary Sunday night into early Monday morning. Timing is still in question but we do have an SPC Day 3 Marginal Outlook for central KY and southern IN with the main threat being strong gusty winds. Due to the timing questions, confidence is rather low at this time but does need to be monitored as we go through the first part of the weekend.

***** LESS HOT, MORE STORMY TO KICK OFF NEXt WORK WEEK *****

A shortwave trough looks to flatten the ridge late Sunday into Monday, bringing better (40-70%) chances for storms as early as Sunday night, and perhaps offering at least limited relief from the oppressive heat and humidity Monday into Tuesday. WPC Cluster analysis suggests that, by midweek, the highest source of uncertainty among long range ensembles (given by PC1 for EOF1) is in the east-west placement of h5 ridging building over the central US and hence: whether our area sees (outcome 1) oppressive heat return or (outcome 2) remains far enough northeast of the ridge to instead see more seasonable temperatures and waves of "ridge-riding" thunderstorms. About 50% of models favor each scenario.

AVIATION /18Z TAFS THROUGH 00Z SUNDAY/

Issued at 126 PM EDT Fri Aug 14 2026

VFR conditions will continue across the region this evening, with a lower confidence precip chance through the afternoon. LEX and RGA have the best chance for an isolated shower or storm, so have utilized PROB30 groups there. SDF could see a shower too, but chances were less, so decided to keep their TAF dry for now. Otherwise, VFR continues tomorrow with light winds from the south.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory from 11 AM EDT /10 AM CDT/ Saturday to 9 PM EDT /8 PM CDT/ Sunday for KYZ023>031-034-038-039-045-046-053- 054-061>065-070>077-081. Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for KYZ023-024-026>028-053-054-061>065-070>077-081. IN...Heat Advisory from 11 AM EDT /10 AM CDT/ Saturday to 9 PM EDT /8 PM CDT/ Sunday for INZ076>078-083-084-089>092.