textproduct: Louisville

KEY MESSAGES

* Scattered afternoon thunderstorm chances (20-40%) return this afternoon and evening. Torrential rainfall rates and slow moving storms are expected. Localized rainfall amounts over 1 inch may be possible.

* Rain and thunderstorm chances peak Friday into Saturday, especially during the afternoon and evening hours. Slow-moving storms will be capable of locally torrential rainfall, lightning, and gusty winds.

* Outside of storms, heat indices will peak in the 97-103 degree range each afternoon through at least Friday. Moderate heat risk is possible, mainly affecting vulnerable populations sensitive to heat, especially those without cooling/hydration.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 319 AM EDT Thu Jul 16 2026

It is another very warm and muggy start to the day, with KY Mesonet stations reporting mid 70s across the Commonwealth, and SDF sitting at 80F early this morning. The forecast will be similar to previous days, though with the upper ridge weakening, that will promote an increased coverage of afternoon showers and storms today. Strong heating will result in temps peaking in the upper 80s and lower 90s once again, with a humid airmass in place with sfc dewpoints in the mid 70s. This will yield heat indices in the 97-103F range this afternoon, with the hottest temps across the northern half of the area. Moderate to major heat risk is possible, mainly affecting vulnerable populations sensitive to heat, but especially those without cooling/hydration.

A weak cold front will be approaching the area from the north later today, which will add forcing to the region for afternoon convection initiation. Model soundings indicate our diurnal heating could lead to SBCAPE values exceeding 2500 J/kg. However, we continue to see very weak flow in the atmospheric column, really no more than 15- 20kts, and this will continue to provide weak shear parameters and very slow storm motions. High PWATs, combined with the high CAPE values, will encourage scattered showers and thunderstorms today, though the lack of shear will likely keep convection less organized. DCAPEs near 1000 J/kg pose a microburst/localized wind threat, though questions remain on how well any storm can organize in this environment. The slow storm motions with high PWATs will support localized torrential rain rates, and while it will not be a washout today, some areas could see some very localized high rainfall amounts over 1 inch as suggested by the HREF LPMM. PoPs for today range between 20-40%, with portions of the Bluegrass (northeast of Lexington) possibly remaining dry today.

The weak frontal boundary is expected to become nearly stalled across northern KY tonight into tomorrow, and will be responsible for increasing coverage of showers and storms for tomorrow. Scattered to numerous showers and storms are expected to blossom once again tomorrow afternoon in a highly unstable, weak shear environment. PWATs peak tomorrow over 2 inches as the theta-e ridge centers over the Ohio Valley. More torrential rain and slower moving storms are forecast tomorrow. High temps for tomorrow have been nudged down slightly from NBM, but still expect mainly upper 80s. However, with the very humid conditions, heat index values will again be near 100 in most areas.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Issued at 319 AM EDT Thu Jul 16 2026

===== Saturday - Sunday =====

Over the weekend, the general synoptic pattern will features ridging across the western US and troughing across the east, with a stronger sinking shortwave pinwheeling around the parent upper low over Canada and into the northeastern US. A sfc low will track across the Great Lakes on Saturday, and although the associated sfc boundary will remain north of our area during the day on Saturday as is slowly sinks south. We will be within a the center of the high PW airmass with diurnal heating favoring continued rounds of showers and storms. PWATs around 2 inches remain the norm for Saturday, with model soundings suggesting a high CAPE low shear environment as scattered storms blossom across the region throughout the afternoon. Weak flow continues to promote slower storm motions, with torrential rain rates favoring a marginal risk for excessive rainfall.

Rain showers and embedded thunder remain likely through Saturday night as the sfc boundary continues to sink south, and is expected to be parallel to the Ohio River by 12z Sunday. This boundary will continue to provide a local forcing for showers and thunderstorms on Sunday, though we should begin to see the higher PWATs start the decrease some.

Still expect a hot and humid weekend, with highs in the upper 80s and low 90s both days, and sfc dewpoints lingering in the 70s. Forecast dewpoints on Saturday could be close to 80 in some locations. This will continue to yield heat indices in the 98-102 range on Saturday mainly north of the WK/BG Pkwys.

===== Next Week =====

We'll be in the wake of Sunday's cold front on Monday, so that should yield drier conditions for the start of next week. However, another upper level trough looks to deepen across Canada early next week, resulting in another FROPA during the day on Tuesday. This will bring yet another round of showers and storms on Tuesday, but the FROPA could bring a much needed cool down by Wednesday as we get some "cooler" and drier post-frontal air to filter in. Highs on Wednesday could be in the low to mid 80s.

AVIATION /18Z TAFS THROUGH 00Z SATURDAY/

Issued at 134 PM EDT Thu Jul 16 2026

Early Thursday afternoon, isolated showers have developed across portions of central Kentucky and southern Indiana. These should percolate during the remainder of the afternoon, potentially (30% chance) producing diminished visibility and a few lightning strikes at/near the airfields through 01z. With enough clearing overnight, GLAMP guidance suggests fog may develop, however didn't have enough confidence to include those in the TAFs, except at HNB where HREF probabilities for sub 1/2 mile visibilities were highest (20-30%).

LMK WATCHES/WARNINGS/ADVISORIES

KY...None. IN...None.