textproduct: Louisville

KEY MESSAGES

* Today through Tuesday, temperatures are expected to warm into the mid 80s to low 90s. Some daily max temperature records could be challenged. * This afternoon/evening, showers and/or thunderstorms arrive, especially for our northwestern counties.

* A line of strong to severe storms is expected to move through ahead of a cold front on Tuesday, possibly bringing strong winds and hail. The line will weaken as it moves east over the region.

SHORT TERM /THROUGH TONIGHT/

Issued at 509 AM EDT Mon May 18 2026

Today, a closed low within an upper trough is located near the Four Corners. East of the trough, southwest flow stretch over the Plains before meeting an upper ridge flowing through the Great Lakes and New England regions. The Lower Ohio Valley sits under this ridge with gusty (20-25 mph) southerly winds being driven by a pressure gradient between a surface high over the Southeast and low pressure that stretches from the western Plains into the Midwest. This sit-up is expected to provide lots of sunshine and WAA to drive high temperatures into the mid 80s to low 90s throughout southern Indiana and central Kentucky.

By this afternoon, the southern low level winds will not only drive temperatures warmer, but they will also lift precipitable water values to 1.75-2" over western Kentucky north into western Indiana, and as the remnants of the system currently over Iowa drift southeast towards the CWA, it will have this moisture rich unstable environment to work with to bring showers and thunderstorm to southern Indiana. Moisture is expected to quickly drop off south of the Ohio River, so most of the activity is expected to remain in southern Indiana, and the best chances for strong to severe thunderstorms will be in the far northwestern parts of the CWA, including Dubois County, where thunderstorms could develop ahead of the approaching line.

With MLCAPE values around 1,600 J/kg, MUCAPE values near 2,300 J/kg, an inverted "V" sounding with LCLs near 1 km, strong winds and hail could be possible. Deep layer shear is weak around 25 knots, so this could possibly help some hail to melt as it fall back through the column, reducing its size. The high PWATs will also likely drive intense rainfall which could cause ponding of water. There is a limited window for any stronger storms as instability is expected to quickly drop to the southeast.

Tonight, any remaining showers and thunderstorms are expected to dissipate. Continued WAA with some cloud cover will help limit cooling, keeping low temperatures in the upper 60s to low 70s.

LONG TERM /TUESDAY THROUGH SUNDAY/

Issued at 509 AM EDT Mon May 18 2026

Tomorrow, ahead of an approaching cold front, temperatures are expected to once again climb into the upper 80s to low 90s with another day of gusty WAA. This is expected to drive very high instability in the area of SPC's "Slight" risk. Some areas over southern Indiana could see MLCAPE values near 2,500 J/kg and MUCAPE values near 3,000 J/kg. This would help an expected line of convection ahead of the front to generate strong gusty winds and possibly large hail before weakening as the system pushes off to the east. Current timing has the line reaching Dubois county during the early afternoon. In the following hours, the line would push east through southern Indiana and central Kentucky.

Tuesday night, the cold front is expected to reach our southern Indiana counties, but it could be slow getting through central Kentucky, not making it through the CWA until sometime on Wednesday. The front will slowly veer winds towards the north. Temperatures will remain mild Tuesday night falling into the mid to upper 60s, but Wednesday's highs can be expected to see some relief only making it to the mid 70s near Jasper, Indiana to the mid 80s near Clinton County. This will be near normal for many across the CWA. The slow moving front will keep shower and thunderstorm chances across the CWA through Wednesday, but strong storms aren't expected.

On Thursday, highs are expected to be slightly below normal, in the low to mid 70s for most. Far southern Kentucky could see the upper 70s. Enjoy it because temperatures begin to inch back up day by day into the mid 80s by Sunday. Precipitation chances remain low but remain as the front sits south of the CWA. Another low pressure system could swing through on Friday, brining a better chance for widespread rain.

AVIATION /12Z TAFS THROUGH 18Z TUESDAY/

Issued at 734 AM EDT Mon May 18 2026

VFR conditions are expected to remain through the period at most sites, but HNB could see a line of afternoon and/or evening convection. This could bring heavy showers and low VFR ceilings for a limited time. The line is expected to dissipate before reaching SDF, so we will keep monitoring this. Something could be added to SDF in the next TAF. All area TAF sites can expect southerly winds to become gusty, gusting to 20-25 knots for most of the day before easing tonight.

LMK WATCHES/WARNINGS/ADVISORIES

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