textproduct: Louisville

KEY MESSAGES

* Showers and thunderstorms will return late tonight into Saturday. Strong to severe storms capable of locally damaging winds or isolated tornadoes are possible Saturday afternoon into Saturday evening. Localized flooding is possible as well. * Additional storms are possible through much of next week, although severe weather is not expected at this time.

SHORT TERM /THROUGH SATURDAY/

Issued at 121 AM EDT Fri Jul 31 2026

Today will be a transition day across the region, as the surface ridge responsible for a nice reprieve from the humidity will begin to scoot to the east. In response, winds today will turn to the south/southeast which will usher in slightly warmer and more humid conditions, although it will still be quite pleasant for this time of year!

Overnight tonight and into Saturday things become more active as a vertically stacked low pressure system approaches the region. Moisture advection will increase on the nose of a 30-35 knot low-level jet Saturday morning, resulting in a fairly solid band of showers and embedded thunderstorms Saturday morning. Forecast soundings suggest this activity should be well elevated above a stable boundary layer, so do not expect any severe weather with this. However, a fetch of deep Gulf moisture will be advected into the region on the nose of the LLJ, resulting in PWAT values climbing above 2 inches, which means the main threat with this initial band would be some locally heavy rainfall.

Confidence continues to slowly increase for severe weather potential on Saturday afternoon into early Saturday evening. It appears there will be enough surface moisture advection and breaks in the clouds to produce a thin, but sufficient instability axis ahead of the occluded cold front. The latest HREF and REFS guidance suggests an 80-90% chance of at least 1,000 J/kg of SBCAPE, and around a 50% chance of 2,000 J/kg. Each suggest generally 1,000-2,000 J/kg of MLCAPE as well. Deep layer shear should be on the order of 25-35 knots, which should be just enough to support organized convection.

Convective mode and associated threats are a little more uncertain. The deep layer shear vectors should be largely parallel to the front, which suggests perhaps a cellular mode at least at first. But the front will be fairly strongly forced as PVA overspreads the frontal surface with the incoming closed low. Therefore, think with time the storms may form more into linear clusters. Think damaging winds will be the main threat, but forecast hodographs due show some concern with backed low level winds (especially within the high resolution guidance) contributing to 150-200 m2/s2 of effective SRH, especially across the northern part of the CWA closer to the surface low (albeit where instability will be a bit weaker). Therefore, cannot rule out a couple tornadoes in this set up either, especially if we do see some breaks in the clouds to help boost up 0-3km CAPE values (currently progged to be at 100-150 J/kg). SPC has upgraded parts of the region to a slight risk for the damaging wind threat, but can't rule out a 5% tornado risk might be needed in future outlooks, especially if the surface low tracks closer to the northern edge of the CWA.

LPMM data from the 00Z HREF does show some pockets of 4+ inches with each of these rounds, so we cannot rule out some localized flash flooding with this system either. However, I do expect there to be a several hour break between the first and second rounds, so that should help limit any high impact flash flood concerns given these storms should have some good movement to them.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

Issued at 121 AM EDT Fri Jul 31 2026

The upper level low unfortunately will hang with us through midweek, keeping chances for showers and a few thunderstorms in the forecast through midweek, mostly diurnally driven. The low should finally meander to the east by Thursday, with lower chances for precipitation to end the workweek. High temperatures will steadily climb through the week, with upper 80s to near 90s expected by the end of the workweek.

AVIATION /06Z TAFS THROUGH 12Z SATURDAY/

Issued at 102 AM EDT Fri Jul 31 2026

Tranquil conditions will persist for the rest of the overnight into much of Friday. Calm winds this morning will give way to SSE winds through the day today. Upper level clouds will work in through the day, with a solid mid-level deck expected by tonight. Introduced some Prob30 groups late in the valid TAF period for HNB and in the planning period at SDF for some -SHRA that will spread across the region tonight into Saturday morning.

LMK WATCHES/WARNINGS/ADVISORIES

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