textproduct: Louisville

KEY MESSAGES

* There is a level 2 of 5 (slight) risk for severe thunderstorms west of roughly I-65, with a level 1 of 5 (marginal) risk elsewhere. The primary hazard would be damaging wind gusts between 8pm and 1am tonight.

* Thunderstorms tonight will also bring a level 2 of 4 (slight) risk for excessive rainfall, with pockets of over 4 inches potentially resulting in flash flooding. Additional waves of storms will prolong the flooding risk through at least Saturday.

* Decreasing chances for afternoon showers and storms and seasonable temperatures are expected Sunday through the middle of next week.

SHORT TERM /THROUGH SATURDAY NIGHT/

Issued at 212 PM EDT Thu Jul 9 2026

At 2pm EDT, central KY and southern IN was situated between two disturbances: a shortwave mid-level trough over the Appalachians and a more potent disturbance along the MS River - the latter will bring storms into our area mid-late this evening. SPC's mesoanalysis reveals anywhere from 500-2000 J/kg MLCAPE (highest values to the west) across the area, which, despite only 15-25 kt effective shear, may support a couple strong to marginally severe thunderstorms. The CAMs generally advertise a multicell/linear storm mode which would suggest wind is the primary hazard, though there is a nonzero tornado risk across the west where there could be a couple hours' overlap between waning diurnally-driven instability and 20-25 kt 0- 3km line normal shear during the 8pm-1am EDT timeframe tonight.

The evening storms should weaken as they move east across the area with the loss of instability, especially if the outflow surges out ahead of them as several CAMs suggest. This outflow should serve as a focus for additional thunderstorms overnight, though the primary concern with those will be heavy rainfall rather than wind, hail, or tornadoes. Recent model trends have been further south with the evening wave of storms and associated outflow - possibly far enough south to confine the best flash flooding risk across Tennessee where the NAM/RAP depict a 30-40 kt LLJ beginning around 4am EDT Friday. Nonetheless, there are still a few models that keep that moisture transport axis - and hence maximum rainfall totals - further north with the HREF ensemble max giving localized pockets of 5+ inches (sufficient for substantial flash flooding) as far north as the IN/KY state line. Needless to say, the WPC level 2 of 4 (slight) risk for excessive rainfall across our area seems reasonable.

As the shortwave trough responsible for all of the showers and storms tonight into tomorrow morning shifts off towards the east, we should see a break in convective activity, though a couple isolated storms remain possible (20-30% chance) during the afternoon. By evening, however, additional waves of storms are slated to fire upstream and propagate east-southeastward along the boundary left in the wake of morning storms. Given the environment - characterized by PWATs of 1.9-2.0 inches, a deep (>12 kft) warm cloud layer, and weak (10-20 kt) deep layer shear - storms will be efficient rainfall producers and rather slow moving, which suggests heavy rainfall is again a concern, particularly Friday night into Saturday. By Saturday morning, HREF/REFS ensemble max 24-hour rainfall depicts pockets of 4+ inches once again; any areas that received heavy rainfall Thursday night-Friday will be particularly vulnerable for additional flash flooding if they receive training storms again with this second wave Friday night into Saturday. Still, there remains potential for the heaviest rainfall amounts to once again occur south of the local area if the effective boundary pushes south as some of the CAMs suggest. At this time, the National Blend of Models (NBM) advertises a 40-70% chance (highest across southern KY) for rainfall totals over 2 inches by 12z/8am EDT Saturday across the local area.

Once again, additional heavy thunderstorms are forecast Saturday afternoon and evening as another shortwave trough and attendant surface low drifts towards the area from the northwest. The Low Resolution Ensemble Forecast (LREF) system mean brings 25-30 kt 0- 6km shear with this system, which combined with 1500-2500 J/kg MLCAPE would favor a severe weather risk during the afternoon, mainly from locally damaging winds in water-laden downbursts. Given the deep moisture in place (PWATs 1.9-2.1 inches), we'll still have to watch for locally heavy rainfall in these storms which could once again trigger flooding, especially if it falls on areas that already received heavy rainfall between tonight and Saturday morning.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

Issued at 212 PM EDT Thu Jul 9 2026

As we head into the second half of the weekend, upper-level ridging will continue to build across the western and central CONUS as an upper level low becomes cutoff over the Tennessee Valley. At the surface, a quasi-stationary boundary is expected to lay out over the Tennessee Valley, though the exact positioning of this boundary will likely be modified by convective episodes Friday and Saturday. To the north of the Ohio Valley, high pressure will try to sink south, along with drier air. There should be a fairly strong north-south gradient in moisture/PW values on Sunday, though the rich (1.75+" PW) moisture which will be over our area the next few days should settle to our south by Sunday. There should still be enough moisture and instability in the area for scattered storms to develop Sunday afternoon, with the greatest coverage expected in southern KY. Weakening flow aloft should limit the severe weather potential, with more of a pulse/typical summer time storm setup expected. The slower storm motions will support a continued threat for flash flooding, though it may be more isolated depending on storm coverage.

For the first half of next week, 600+ dm upper ridging will spread into the northern Plains, controlling much of the weather across the CONUS. The pattern over our region will be a bit more complex. An increasing proportion of the medium-range ensembles keeps an upper- level low meandering across the TN Valley through much of the early week, and while moisture won't be particularly rich (PW 1.25-1.5"), there could be enough combined forcing and moisture for isolated to scattered afternoon and evening convection Monday and Tuesday. Temperatures are expected to be fairly seasonable through the middle of next week, with highs ranging from the mid 80s to around 90 Sunday through Wednesday. With less moisture content in the air, nighttime temperatures should be able to cool into the upper 60s and low 70s each night.

AVIATION /18Z TAFS THROUGH 00Z SATURDAY/

Issued at 135 PM EDT Thu Jul 9 2026

As a low pressure system approaches, scattered thunderstorms (50-70% coverage) will overspread the area tonight, bringing periods of reduced visibilities. Ceilings are also likely (60-80% chance) to drop into the MVFR category by around 12z/8am EDT Friday. Convection should be tapering off by around that time, though a few lingering storms are possible (20-30% chance) through the end of the flight period.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Flood Watch through late Saturday night for KYZ023>043-045>049- 053>057-061>067-070>078-081-082. IN...Flood Watch through late Saturday night for INZ076>079-083-084- 089>092.