textproduct: Louisville

KEY MESSAGES

* A Heat Advisory is in effect for areas west of a Jasper, IN to Scottsville, KY line on Tuesday afternoon and evening. Max heat index values around 105 degrees are expected.

* A northwest flow pattern aloft will take residence across the region for much of the upcoming work week with clusters of showers and storms impacting portions of the central and eastern Ohio Valley. Across west-central Kentucky, dry and hot conditions are expected.

* Storms that develop will likely be strong/severe with torrential rainfall, intense lightning, and the potential for damaging winds. The highest risk of severe weather for later tonight through Tuesday night will be across southeastern Indiana and into portions of far northern Kentucky.

* Multiple clusters and/or wave of storms will likely train across portions of IN/OH and KY this week. This will lead to excessive rainfall and flash flooding. Locally, the highest risk for flooding would be across our northeastern portions of the forecast area (SE IN and the Bluegrass region).

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 256 PM EDT Mon Aug 10 2026

Things are quiet across the CWA at this hour as we sit between upper ridging to our south, and low amplitude NW flow to our north. The current pattern features enough of a H85 subsidence inversion along with the lack of any notable triggers to likely keep us dry the rest of today and tonight. We will have to watch the upstream MCS over OH/WV, as some data indicates re-development could occur on its western flank later this evening and then backbuild SW into our CWA later tonight. The bulk of these solutions is offered by NAM based CAMs, and so far, that model has been too far west and south with its MCS development, so will put that in the "less likely" scenario category for now. Still, something to monitor.

Temperatures have surged into the upper 80s and low 90s across the area, and with dew points running well into the 70s, especially west of I-65 we are seeing some heat indices creep into the 100 to around 105F range. Elected not to go with a Heat Advisory for counties west of I-65 today as we'll likely only peak there for an hour or two this afternoon, however have issued a Heat Advisory for tomorrow for locations along and west of a Jasper, IN down to Scottsville, KY line.

In addition to the heat and humidity for tomorrow, focus will continue to be on potential MCS activity. It is possible that an MCS flirts with our NE CWA by mid to late Tuesday morning, however this would likely be in a weakened state, and is only low confidence on affecting our area at all. The bigger focus/concern will be with an expected stronger MCS by early evening, perhaps lasting into the overnight. This complex would be triggered by a shortwave embedded in the NW flow aloft, that most of the models seem to agree on. Given that we will be strongly unstable (ML CAPE 3000-4000 J/KG) combined with at least 30-40 knots of mid to upper level flow that setup seems right for a developing upstream MCS to forward propagate into our area thanks to favorable shear for updraft/cold pool balance. This system would carry mainly a damaging wind threat (perhaps widespread if the cold pool really gets going), however a Flash Flood threat could develop if western portions of the MCS stall and become more parallel to the upper flow. Considered a Flood Watch for our NE CWA, however confidence isn't quite high enough to take it that far SW just yet. Thanks to ILN/JKL for collaboration on that.

The other area of uncertainty is how deep into the night, and how far west any MCS activity might make it. It is possible that an early damaging wind threat in the evening, transitions to a Flash Flood threat deeper into Tuesday night thanks to storms backbuilding against the upper flow. The 10/12z HREF 48 Hr QPF Max ensemble member does suggest some very high localized amounts, however the PMM data isn't quite on board with the extreme values. It does suggest some pockets of 3-4" in localized areas and that is likely what we will continue to message unless confidence changes either way.

LONG TERM /WEDNESDAY THROUGH MONDAY/

Issued at 256 PM EDT Mon Aug 10 2026

Wednesday - Friday Night...

Upper ridging will hold over south central CONUS through mid to late week, and we'll continue to see a NW flow pattern over our region on the NE periphery of the upper ridge. This will put us in the game for continue MCS potential through late week, however much will depend on the evolution of each previous system, and how far south and west into the ridge each convectively reinforced boundary / cold pool can make it. For now based on pattern recognition, our NE half of the CWA looks to be the most likely to experience a severe weather threat (primarily damaging winds), along with potential flash flooding if repeated rounds of convection start to add up and/or, the western flank of any MCS stalls and becomes more parallel to the upper flow.

Across our SW CWA, we are expected to be deeper into the upper ridge, and therefore expect an overall hotter and drier pattern. Although, a strong MCS could wreck this scenario at any point mid to late week. For now, feel the more likely scenario will be better chances of getting into the low to mid 90s each day. These temps combined with dew points expected to be in the low and mid 70s will create some heat index values peaking around 100 to 105 degrees. It is possible we could add a tier or two of counties to a Heat Advisory along and west of I-65, but may have to take this a day at a time as low confidence will continue with regard to MCS activity, and the potential to get a cold pool push or convective cloud debris wrecking a temp forecast.

Saturday - Monday...

The upper ridge looks to build heading into the weekend, and center more over the Ozarks. As this occurs, it will assert more influence into our region, which should lead to a hotter/drier type of setup for the weekend. The good news is that it should lessen the threat of MCS activity across our area, however it will likely come with hotter overall temps. Current NBM suggest low to mid 90s by Sunday. Some Heat Advisory headlines would likely be needed, at least for a portion of our area. Along and west of I-65 would be the best candidate.

By Monday, the upper ridge may flatten out over our area and retrograde back to the west. As this occurs, a surface frontal boundary trailing from a NE CONUS system may drop into our northern CWA. We could be back in the game for more MCS activity around this time, but not too confident this far out. Temps would likely settle back closer to normal highs for this time of year.

AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 745 PM EDT Mon Aug 10 2026

VFR conditions are expected outside of storms through the TAF period. Gusty winds out of the SW now will weaken overnight with a persistent SW flow of around 5-8 kts. High level clouds will continue to push through the overnight as well. Multiple rounds of storms will be progressing over the upper Ohio Valley come Tuesday morning and how far south these storms progress remains to be seen. For now, there are no PROBs for any precipitation until later tomorrow afternoon and evening for all terminals except HNB and BWG. By then, a main line of storms will push in from the northeast bringing gusty winds and brief MVFR ceilings. Otherwise, VFR conditions with SW winds gusting 20-25 kts is expected through tomorrow evening.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory from 11 AM to 8 PM CDT Tuesday for KYZ023-026- 061-070>073. IN...Heat Advisory from noon EDT /11 AM CDT/ to 9 PM EDT /8 PM CDT/ Tuesday for INZ083-089.