textproduct: Louisville

KEY MESSAGES

* Strong to severe thunderstorms will be possible this evening into tonight. Damaging winds, isolated tornadoes, and flash flooding are the main threats.

MESOSCALE

Issued at 1022 PM EDT Sun Jun 21 2026

Line of severe convection continues to push eastward across southern Indiana at this hour. Looking at LVX VAD profile, we've seen an increase in the low-level wind field over the last hour with SRH increasing into the 400-500 m2/s2 range. MUCAPE via mesoanalysis continues to show about 1000-1500 J/kg. With the MCV moving into east-central IN, continued theta-e advection and the nocturnal low- level jet should continue to support ample buoyancy to sustain current convection despite the loss of daytime heating.

Atmosphere to the east of I-65 has become a bit more stable as theta- e air over there is of lesser quality. However, best combo of shear/instability resides back to the west of I-65 from north of Louisville back toward Evansville. Still watching a pair of supercells with ample rotation. The first is over NE Perry IN heading east into southern Crawford. The second is out east of Evansville. Both of these cells are on the southern side of the convective line with no real interruption of moist warm flow on the inflow flank. A more east-west oriented line of convection stretching from Gibson county east down I-64 continues to move southeast and may end up catching up with the more discrete supercells over time.

Further northeast in the lower theta-e air, strong convection will move out of southeast Indiana and into portions of northern KY. While further displaced from the low-level jet, cold pool development may promote an uptick in wind gust potential across portions of north-central KY from Oldham county eastward into the western Bluegrass region.

Training of convection back along the I-64 corridor may result in an increased hydro threat across portions of southern Indiana over the next couple of hours.

Issued at 844 PM EDT Sun Jun 21 2026

Cluster of multi-cellular and supercellular storms are currently in progress across southern Indiana this evening. Environment across our northwest/northern CWA (focusing on southern IN) remain in a favorable environment for continued tornado production. Effective layer shear values on the order of 40-45kts and 0-3KM ESRH values of 350-400 m2/s2 (based on VWX VWP) remain in place across the region. Much of this low-level enhanced flow is being driven by the convectively generated MCV moving across central IN. So the storms should continue to maintain themselves up to the I-65 corridor. East of the I-65 corridor, mesoanalysis shows that low-level theta-e drops off quickly and storms most likely will become elevated and reverting from more of a tornado threat to a wind damage threat.

Further west, a more discrete supercell is in progress across portions of Gibson/Pike county. It remains in a favorable shear/instability axis and will affect Dubois county over the next hour.

Overall, the next 1-2 hours of focused severe weather will remain north of the Ohio River across southern Indiana. The cluster of storms will eventually move into SE IN and into portions of northern KY by 230-330Z.

SHORT TERM /THROUGH MONDAY/

Issued at 355 PM EDT Sun Jun 21 2026

Ahead of a surface low, currently over northern Missouri, is an area of convection stretching from St. Louis up through Peoria. Into the overnight, this low will get pushed towards central Indiana by junkie zonal flow and is expected to push the line of convection towards southern Indiana and central Kentucky.

Ahead of the line, in southern Illinois and far western Kentucky dew points are in the mid 70s. They taper off into the mid 60s over southern Indiana and central Kentucky. Temperatures over the CWA are in the low to mid 80s but will continue increasing a few degrees being lifted by southern winds and mostly clear skies ahead of the system.

Model agreement has improved greatly from 24 hours ago. CAMs have the main line entering our southwestern Indiana counties around 23- 00z and continuing to push east and south through the CWA tonight. This is entering an environment with crazy high precipitable water values of 1.8 to 2.25+ inches. Anything near 2 inches is a lot and has to put flash flooding concerns on the mind, so any place that sees training storms, multiple waves, or slow moving storms could pick up multiple inches in a short amount of time. Our 6 hours Flash Flood Guidance ranges from 2.5 to 6 inches over southern Indiana and central Kentucky with our southwestern counties, near Bowling Green, being able to take that higher amount. Where we have the Flood Watch in Indiana is closer to the low and where the higher chances currently are for flooding. The flooding threat may end up being the greatest threat this evening/tonight.

On the severe weather side, model soundings and hodographs dynamics look favorable for tornadoes over southwestern Indiana. Deep layer 0- 6 km shear is over 40 knots. There is good turning with good inflow in the low levels of the hodograph and low level SRH values are high, but with the expected arrival of the line being when we lose diurnal warming near sunset, a stable layer is expected to develop at the surface. There will be a point to our west moving into our area that surface based storms become more elevated where it will be harder to get a tornado to the ground. LCLs are lower in some of the guidance than they has been, and overall, instability remains fairly weak with MLCAPE remaining under 1,000 J/kg. The better instability remains south of Interstate 64 and west of Bowling Green. Believe it's possible the stronger convection ends up missing a good chunk of the CWA as convection chases the instability south through western Kentucky while some activity stays with the low moving over central Indiana.

By around 6z or a little after, the bulk of the convection will likely be south and east of the CWA. For the rest of the night, ceiling are expected to be low with isolated to scattered showers likely.

Monday, the system's cold front will lag on the back side of the low and is expected to push through during the afternoon hours. This will veer winds towards the northwest, limiting highs to the mid to upper 70s over southern Indiana and the low 80s over southern Kentucky. Additional waves of showers and non-severe thunderstorms will remain possible through Monday.

LONG TERM /MONDAY NIGHT THROUGH SUNDAY/

Issued at 355 PM EDT Sun Jun 21 2026

By Monday night, CAA is over the CWA as a large surface high gets pushed east from the Plains through Indiana by Tuesday night. This will bring a return of WAA on Wednesday, lifting temperatures that were slightly below normal Tuesday and Wednesday back to near normal by Thursday.

The CWA is expected to remain dry through Wednesday, but as the high pushes off the the east, zonal flow will push small surface lows from the Plains through the Ozarks into the Lower Ohio Valley. It don't look like a washout, but shower and thunderstorms chances will increase during this period. Towards the end of the week, a strong ridge will likely bring warmer temperatures and drier weather.

AVIATION /00Z TAFS THROUGH 06Z TUESDAY/

Issued at 748 PM EDT Sun Jun 21 2026

VFR conditions will continue from now until a broken line of storms approaches from the west near 01Z at HNB, to near 05Z in south and eastern airports. These storms will bring MVFR ceilings and variable winds gusting up to 35kts or higher if individual cells turn severe. Once the showers or storms roll through all airports, ceilings will lower to low end MVFR and high end IFR, with the lowest ceilings in the NW near HNB. Winds will continue to blow from the S/SW until the storms end, eventually turning out of the west later Monday afternoon. Ceilings are slow to recover if much at all during the day on Monday remaining in MVFR category through the afternoon. Thunderstorms may refire in BWG/RGA later in the day, but otherwise airports remain dry with MVFR conditions expected Monday afternoon.

LMK WATCHES/WARNINGS/ADVISORIES

KY...None. IN...Flood Watch until 8 AM EDT /7 AM CDT/ Monday for INZ076>079- 083-084-089>092.