textproduct: Louisville

KEY MESSAGES

* Hot and humid conditions into the weekend with highs in the low/mid 90s with heat index values up to 109 degrees both days. Heat Advisory is in effect this weekend for a large portion of southern IN, central and southern KY.

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

* Another round of showers and storms are possible late Sunday ahead of a cold front moving through the region. Any storms that become severe would be capable of producing damaging winds.

* A reprieve from the hot and humid weather, as well as showers and storms, comes Monday afternoon once the cold front departs to the south.

SHORT TERM /THROUGH TONIGHT/

Issued at 405 AM EDT Sat Aug 15 2026

A few very isolated showers have developed in the Bluegrass this morning along a weak frontal boundary extending across central Kentucky to far southwestern Indiana. Conditions have otherwise been calm, with the additional exception of some patchy fog south of Lexington and near I-75 that will quickly dissipate by sunrise.

Looking broadly, the region is currently under an upper ridge that is set to last into the latter parts of the weekend. Over the course of the day on Saturday, the previously mentioned frontal boundary will lift northward, allowing surface flow across the region to shift from the NNE to the SW, bringing in additional hot and humid air. While record high temperatures are not in danger of being broken with this current pattern, dew points in the low-to-mid 70s will allow heat indices to rise well into the 100s. A Heat Advisory is in place for the western 2/3 of the CWA for heat indices up to 109 Saturday, beginning at 11 AM EDT/10 AM CDT. For areas not in the advisory, conditions will still be uncomfortable. HREF probabilities for heat indices over 100 are greater than 70% for most of the area, so be prepared if you plan to go outside for extended periods of time. There would be two potential limiting factors to how high heat indices could get: 1) low-level mixing from clear skies in the southern CWA that would decrease afternoon dew points and lower heat indices; 2) building cloud cover over the northern CWA from an incoming system currently over Illinois, Iowa, and Missouri that would limit maximum temperatures.

Speaking of the system off to our west, that will move eastward over the day on Saturday, with its southern periphery passing over southern Indiana. While ample instability (HREF mean CAPE > 2000 J/kg) will be in place, generally weaker wind shear will limit how strong these storms will be able to get. The SPC has a very small area in the NE portions of the CWA in the Bluegrass under a Slight risk for severe weather, with places west in a Marginal Risk or general thunder area for the convective outlook. Most places will remain dry, especially as you go south and west in the region, but a few showers and isolated storms cannot be ruled out to the north along and north of the Ohio River.

For Saturday night, another impulse will ride the ridge over the Midwest and upper Ohio Valley, presenting another chance for isolated to widely scattered showers and storms across the northern portions of the CWA. Overnight temperatures will not recover much, with lows only dropping into the mid 70s. Conditions along and south of the Parkways will be dry, but also muggy with fairly weak winds forecast.

LONG TERM /SUNDAY THROUGH FRIDAY/

Issued at 405 AM EDT Sat Aug 15 2026

For Sunday, the upper ridge will continue to hold over the region, allowing more uncomfortable heat and humidity to persist over the region. Recent ensemble guidance suggests slightly higher afternoon temperatures in comparison to Saturday, with low to mid 90s in southern Indiana and north-central Kentucky, and mid-to-upper 90s over south-central Kentucky. HREF probabilities for heat indices at or above 105 increases to greater than 85% for our western CWA, though chances for heat indices above 110 remain low (<15%). The Heat Advisory beginning later Saturday lasts through Sunday evening until 9 PM EDT/8 PM CDT.

In terms of chances for precipitation, the region will be in between two disturbances during the daytime hours on Sunday, especially south of the Ohio River. As a result, conditions will be mostly dry through most of the day before the frontal boundary of a disturbance over the NE CONUS pushes southeastward across the region late Sunday into Sunday night. Ample instability will be in place out ahead of the front (HREF mean CAPE > 2500 J/kg), though weaker wind shear (<30 kt of deep-layer shear) could limit the extent of stronger storm activity. The one thing that can counteract this some is that an area of >2" PW will develop ahead of the front over southern Indiana and north-central Kentucky. While widespread showers and thunderstorms are not expected late Sunday, isolated to widely scattered showers and storms capable of producing heavier downpours, gusty winds, and frequent lightning are possible in the northern CWA. The SPC has also put out a Slight Risk for severe weather for southern Indiana and north-central Kentucky due to this potential.

Once the cold front moves through Sunday night through Monday, weak surface ridging and northerly surface flow will bring a much-needed reprieve from the hot and humid conditions we've been experiencing. Over the early portions of the workweek, dew points will decrease from the 70s to the 60s, with afternoon highs only in the mid-to- upper 80s. A few isolated showers and a rumble of thunder will be possible over southern Kentucky late Monday, with remaining chances of precipitation departing Monday night.

For Tuesday and most of Wednesday, surface ridging will keep conditions dry and temperatures near-normal for this time of year. Leading up to late Wednesday, a broader pattern shift will take place. Across the CONUS, ridging over the west will amplify through the end of the workweek as troughing digs over the Midwest/Ohio Valley/NE CONUS. This will help set up a more unsettled pattern for our region, with slight chances for showers and storms Wednesday afternoon and lasting through the remainder of the workweek. Temperatures will remain at or below-normal during this stretch, allowing for a continued reprieve from uncomfortable heat and humidity.

AVIATION /12Z TAFS THROUGH 18Z SUNDAY/

Issued at 703 AM EDT Sat Aug 15 2026

VFR conditions will prevail for most of the TAF period. Patchy fog has been near RGA since around 05z, but should quickly dissipate in the next hour or two. For all terminals except BWG, winds have begun to shift from the NNE to the SW, and will slowly increase during the day Saturday. For BWG, winds will remain out of the south, steadily increasing during the day. There is an ~20% chance for a few showers and an isolated storm to occur near LEX, RGA, and SDF, but confidence was too low to include in the TAF. Chances for showers and storms will quickly decrease after sunset Saturday evening, with dry conditions expected through the remainder of the TAF period.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory from 11 AM EDT /10 AM CDT/ this morning to 9 PM EDT /8 PM CDT/ Sunday for KYZ023>031-034-038-039-045-046- 053-054-061>065-070>078-081-082. IN...Heat Advisory from 11 AM EDT /10 AM CDT/ this morning to 9 PM EDT /8 PM CDT/ Sunday for INZ076>078-083-084-089>092.