textproduct: Louisville

KEY MESSAGES

* Strong to severe storms will be possible later Sunday afternoon into late Sunday evening. All severe hazards could be in play, especially along and west of I-65 and north of the WK/BG Parkways.

* A somewhat unsettled pattern is expected through early week with temperatures slightly below normal and off and on shower and storm chances possible, especially across southern KY.

SHORT TERM /THROUGH SUNDAY/

Issued at 416 PM EDT Sat Jun 20 2026

Through the rest of the evening and into tonight, northwest flow will push a weak cold front south through southern Indiana, ahead of a small surface high, and with precipitable water values between 1.1 and 1.3" ahead of the front, isolated to scattered showers with a few thunderstorms will likely develop. This activity is expected to be limited to along and north of Interstate 64 and will fade early tonight.

The surface high moving into the Lower Ohio Valley will cause westerly winds to become light and variable before becoming more easterly tomorrow morning. Some passing clouds will remain, but clearing skies will lead to some radiative cooling. Temperatures are expected to fall into the low to mid 60s in many places with some areas reaching into the 50s.

Tomorrow, winds begin out of the east to east-southeast as a surface low over the western Plains gets quickly pushed eastward by zonal flow. The increasing pressure gradient over southern Indiana and central Kentucky will continue veering winds towards the south, carrying warm moist air farther northward as a warm front. Partly to mostly sunny skies will drive instability, possibly helping the front develop isolated convection throughout the afternoon and evening hours as temperatures reach into the mid to upper 80s with dew points in the mid 60s to near 70.

LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/

Issued at 416 PM EDT Sat Jun 20 2026

Heading into Sunday evening into the overnight, the aforementioned surface low that was over the Plains gets pushed towards southern Indiana, where it's expected to arrive after midnight. While it does this, the low drags a cold front with it. Ahead of the front, south and southwest winds being driven by a 35-40 mph low level jet lift dew points into the upper 60s to low 70s as precipitable water values climb to over 1.5", reaching up to 2.25" along the front.

There remains a question of how much instability there will be for the approaching front and expected convection to work with. If areas along and north of the Ohio River remain more cloudy, it will reduce instability. The latest model runs have reduced instability values but have an earlier arrival time. Some earlier runs have indicated a later arrival with higher instability and higher DCAPE values, but the later runs also develop a stable layer in the boundary layer. Basically, there remains uncertainty in the the timing. The main threat continues to have a line of convection likely bowing as it moves through the CWA. Strong winds are expected, but the amount of instability available to the line and the time of arrive will determine how strong the line is. It could be the earlier arrival with a developed cold pool that begins outrunning the front, or the line could remain closer to the front, providing for a later arrival.

There is a small threat for a tornado. The best chance for this would be earlier in the evening over southwest Indiana, if convection arrives in time. Model soundings show good instability in the low and mid levels with strong 0-6 km deep layer shear over 50 knots. Hodographs show good backing at the surface. A couple limiting factors are high LCLs (over 1 km) and marginal instability, possibly being only around 500 J/kg.

The other risk tomorrow evening/night will be the flash flooding risk. Anytime Precipitable water values get to near 2", rain can pile up quick. As long as the convection remains generally north and south oriented and quickly pushes through perpendicular to the flow, the flooding threat will remain fairly low, but if the west to east part of the line doesn't continue dropping south and moves more to the east and we have training, there will likely be problems. The best chances for flooding currently look to be over Indiana. The Indianapolis NWS office has already issued a flood watch. This could be expanded south a row or two of counties into our CWA in the future.

As the convection pushes off to the east and south, it's expected to weaken. By Monday morning, the main convection is expected to be out of Kentucky or weakened to mostly just showers before most activity come to an end Monday afternoon.

AVIATION /18Z TAFS THROUGH 00Z MONDAY/

Issued at 219 PM EDT Sat Jun 20 2026

VFR conditions are expected through the forecast period. Winds out of the west will become light and variable tonight as surface high pressure moves into the region. Tomorrow, winds pick back up from the east-southeast before veering towards the south.

LMK WATCHES/WARNINGS/ADVISORIES

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