textproduct: Louisville

KEY MESSAGES

* Showers and thunderstorms will return late tonight and Saturday. Some strong to severe storms are possible on Saturday, along with heavy rainfall and possible flooding issues in spots.

* More scattered shower/storm activity possible through the middle of next week, mainly in the afternoon and evening hours.

SHORT TERM /THROUGH SATURDAY/

Issued at 338 PM EDT Fri Jul 31 2026

Things are quiet across the CWA at this hour. Expect that to largely be the case through the afternoon and evening, however will have to keep eyes west of I-65 where some light rain may make it early this evening before dissipating. Current radar presentation shows precipitation is a bit farther ahead of schedule than models suggest, so elected to bring precip chances a bit farther east as well.

Current water vapor imagery shows an impressive positive tilt shortwave trough sitting over the upper Midwest, with an associated surface low currently over central IA. These features will slide southeast toward our region tonight with the shortwave becoming more neutrally tilted and the surface low settling into central IN by tomorrow. Ahead of these features, a notable 20-25 knot low level jet is expected to overspread our region later tonight beneath the exit region of modest mid to upper level jetting. We'll seeing increasing coverage of showers and some embedded elevated thunderstorm potential from W to E. These are expected to linger through around or a little after sunrise, before we get a bit of a break in coverage through late morning and midday. By this time, do expect to have some breaks in the clouds (mid level dry slot) as shown by the 31/12z HREF. A warm sector will also be getting established over the area by this time with the triple point expect to be somewhere up near our northern or northeast CWA through the afternoon and early evening.

HREF probabilities of ML CAPE values over 1000 J/KG are peaking in the 60-80% range for tomorrow afternoon, with even a 10-20% chance of 2000 J/KG. As a result, do think we'll see modest destabilization of at least 1000-1500 J/KG of ML CAPE by afternoon ahead of the cold front. In addition, surface winds are expected to be locally backed, especially near the the triple point. This will enhance the low level SRH values, and create an overall more favorable hodograph. Even though deep layer shear values aren't overly impressive in the 25-35 knot range, it will likely be enough for organization and some supercell storm modes. Overall, pretty impressed with this early August shear profile, and am a bit concerned about the tornado threat going into tomorrow afternoon and evening. Most concerned up near the triple point where the nose of an instability gradient will coincide with more locally backed surface winds to create some enhanced low level SRH values. Given a high PWAT airmass and a quick look at forecast soundings, LCLs are also expected to be sufficiently low. May be looking for a potential upgrade of the Tornado threat (at least across our NE CWA) if current trends hold. Damaging winds will also be a concern with any more organized updraft, and will likely be the overall broader threat across the rest of the CWA.

Some of the latest data has suggested early afternoon initiation may be confined to areas along and east of I-65, so it is possible that our western CWA gets mostly spared. We'll have to see where the cold frontal position is when things destabilize again around midday. Timing looks to be pretty similar to the previous forecast, but may hang on another hour or so in the eastern CWA. Will likely message 1 to 9 PM EDT.

A final threat we'll have to watch for is a localized flash flooding threat as a very high PWAT airmass (2"+) combined with some loose training potential and somewhat slow storm motion. Do worry that these storms could produce brief several inch per hour rates. 31/12z HREF data does suggest some localized pockets of 4"+ for areas along and east of I-65 through Saturday night.

LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/

Issued at 338 PM EDT Fri Jul 31 2026

Saturday Night - Tuesday Night...

The closed low is expected to cut off from the mean upper flow, and then meander very slowly eastward through the 2nd part of the weekend and into the first part of next week. The bulk of model data suggests this feature could hang around our region through Tuesday before getting picked up by the stronger westerlies associated with a digging north central CONUS trough. The main impact on sensible weather is expected to be lingering showers and a few thunderstorms, mainly each afternoon and evening, however will have to carry some isolated chances each night as well given the high moisture content wrapped up in this system (PWATs around 2"). Given that the best deep layer shear will move off to the east, expect fairly slow storm movement late weekend/early week. A few isolated flooding issues could arise, or pre-existing flooding issues from Saturday may be exacerbated. Expect below normal temperatures (upper 70s and low 80s) under fairly heavy sky cover, and smaller diurnal ranges with overnight lows mostly in the mid to upper 60s.

Wednesday - Friday...

Things will trend warmer for the late week time frame, although there will also likely be a dry period (Wed/Thur is best bet) in this stretch. This will occur as we sit on the southern fringes of a digging north central CONUS trough, and on the northern periphery of an upper ridge. Forecast models loosely suggest an impinging weak frontal boundary trailing from an eastern Canada system or a weak embedded shortwave could rotate into the area by Friday. Given our increased heat and humidity, plenty of instability should be present for shower and storm development. Low confidence on timing or any individual feature, but in general chances for showers and storms should increase into the first part of the weekend. Looking for mid 80s by Wednesday, and highs peaking in the upper 80s and low 90s by Thur/Fri.

AVIATION /18Z TAFS THROUGH 00Z SUNDAY/

Issued at 142 PM EDT Fri Jul 31 2026

VFR continues today and into the evening with a steady S wind and a few mid and upper clouds. Sky cover increases this evening and tonight as a low pressure area approaches from the NW. Surface winds will go light of the SE, with some ceilings setting in overnight.

Showers, and a few embedded thunderstorms are expected in the morning with some MVFR ceilings taking hold of the area. Expect some breaks in the shower heading into the afternoon, however thunderstorm redevelopment is expected by this time. Included prob30s to cover that time period.

LMK WATCHES/WARNINGS/ADVISORIES

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