textproduct: Louisville

KEY MESSAGES

* There is a level 3 of 5 (enhanced) risk for severe weather this evening north of a roughly Bedford, Indiana to Richmond, Kentucky line, with the risk decreasing further southwest. Damaging winds, some significant (> 75 mph), are the primary hazard.

* Repeated rounds of heavy rainfall in thunderstorms tonight and again tomorrow could result in localized flash flooding. There is a level 2 of 4 (slight) risk for excessive rainfall.

* Additional rounds of storms are possible (40-60% chance) through Friday. There is a level 2 of 5 (slight) risk for severe weather tomorrow west of I-65, with damaging winds the primary concern.

* Outside of storms, heat indices are likely (50-80% chance) to surpass 100 degrees west of I-65 each afternoon through Thursday, and area-wide over the weekend.

UPDATE

Issued at 923 AM EDT Tue Aug 11 2026

Severe Thunderstorm Watch #564 will be in effect until 2 PM EDT this afternoon across our far NE CWA (Harrison, Scott, Bourbon, and Nicholas counties). Keeping a close eye on the upstream bowing segment that has latched onto the impressive ML CAPE gradient stretching across SW Ohio into NE Kentucky. Currently, there is enough 0-6 km deep layer shear to sustain some cold pool/updraft balance, however the farther SE the complex tracks, it will start to outrun the best 0-6 km shear and will likely weaken into NE KY. 11/13z Mesoanalysis shows less than 25 knots of 0-6 km shear south of the Ohio River, and we are already seeing some of the outflow outrun the reflectivity over SW Ohio. So, overall not too concerned for our far NE counties, but can't rule out a severe wind threat as the complex weakens into our area late morning to around midday.

SHORT TERM /THROUGH TONIGHT/

Issued at 316 AM EDT Tue Aug 11 2026

***** SEVERE WEATHER RISK THIS EVENING *****

Early Tuesday morning, upper level ridging was maintaining seasonably warm and humid conditions across northern Kentucky and southwest Indiana, with temperatures/dewpoints mainly in the upper/mid 70s at 3am. Meanwhile, a weak mid level disturbance on the northeast periphery of the ridge triggered storms over portions of Ohio into West Virginia. Northwest flow aloft should continue to carry these southeastward across West Virginia - keeping them out of our local area; however, the HRRR and NAMNest - the two models best handling the placement of current convection - suggest redevelopment upstream over northern/central Indiana toward daybreak, and this second wave could affect our local area during the morning into early afternoon. Convective allowing models (CAMs) disagree on precisely how much of our area sees early day activity with this wave, with the HRRR and ARW merely grazing our northeast counties, the RRFS hitting areas northeast of a roughly Louisville to Richmond line, and the NAMNest bringing a decaying line south across virtually the entire CWA. Given the mean wind is generally out of the west- northwest (around 280-290 degrees), and having seen the NAMNest overdo an MCS's right turn into higher theta-e air several times in the past, our forecast leans towards the HRRR/ARW solution, with just a low (20-30%) chance of a storm east of Madison, IN to Lexington, KY line mid morning-early afternoon.

The evolution of this morning activity will be critical in dictating the trajectory of the next and potentially more impactful wave of storms this evening into tonight. The large-scale set-up: A shortwave trough embedded within broad west-northwest flow will provide lift to trigger storm development across Iowa/southern Minnesota/southern Wisconsin this morning, with that activity generally favored to spread southeast along the instability axis during the afternoon and evening. If early day activity stays to our northeast, the effective boundary (and hence instability gradient) should keep the focus for evening storms across central/northern Indiana and much of Ohio; however, if we have more in the way of early day storms, evening storms could take a right turn and dive south along the remnant outflow boundary. In either case, some guidance - most notably the most recent (04z) HRRR iteration - suggests these afternoon and evening storms will develop a strong cold pool, and produce widespread damaging winds (with some locations seeing gusts > 75 mph) wherever they track. Based on the best overlap of shear and instability, the most favored corridor would be just northeast of our local area, but given the uncertainty and potential for significant impacts the SPC has areas north of a roughly Bedford, Indiana to Richmond, Kentucky line outlooked in a level 3 of 5 (enhanced) risk for severe weather; the slight risk extends southward to a roughly Huntingburg, Indiana to Windsor, Kentucky line. Wind is in CIG 1 hatching, indicating potential for 75+ mph gusts capable of structural (primarily shingle/siding) and significant tree (large trees snapped, many limbs downed) damage, with the latter likely to also result in numerous power outages (from trees/limbs falling on lines). In addition, there is a 2% tornado risk, suggesting a low but nonzero chance of a brief spin up in the line of storms, mainly in the northern portion of any bowing segments where the line becomes nearly orthogonal to 0-3km shear vectors (roughly out of 280 degrees). However, we'd like to reiterate that confidence on storm track is low; there is potential that most/all of this passes to our north, leaving us unscathed.

Outside of storms, it'll be a seasonably hot and muggy day with the HREF/REFS suggesting a medium-high probability (50-80% chance) of afternoon heat indices in the triple digits west of I-65. The greatest potential for heat indices topping 105 should be confined to areas west of a roughly Bedford, IN to Scottsville, KY line, where a Heat Advisory is in effect.

***** FLOODING POTENTIAL TONIGHT INTO WEDNESDAY MORNING *****

Once the forward-propagating portion of the line pushes through (or to the northeast of) the local area, a lingering outflow boundary could serve as a focus for additional storms on the nose of what the RAP/NAM depict as a 30-35 kt westerly LLJ. While upshear Corfidi vectors are 20-30 kt (towards the southeast), which by itself would suggest enough storm motion to keep the hydro risk low, training cells could lead to repeated rounds of heavy rainfall over the same areas if the boundary lays out in a north-south orientation. As with the evening MCS, uncertainty is high in where (and even whether) this will set up, but concern is greatest in areas east of a roughly Madison, Indiana to Lexington, Kentucky line where WPC has a level 3 of 4 (moderate) risk for excessive rainfall, and where the HREF and REFS ensemble max depict swaths of 6+ inches of rainfall in just a few hours tonight into Wednesday morning.

LONG TERM /WEDNESDAY THROUGH MONDAY/

Issued at 316 AM EDT Tue Aug 11 2026

***** ADDITIONAL STORMS WEDNESDAY INTO WEDNESDAY NIGHT *****

Depending on how things evolve tonight, we could have storms ongoing during the morning commute tomorrow, with the effective boundary fueling continued storms throughout the day. However, the highest chance for storms over the local area will once again be during the evening when another shortwave digs across the Upper Ohio Valley, providing a lifting mechanism and better (30-40 kt) deep layer shear to sustain convection. Uncertainty surrounds how much of a severe risk will accompany this activity given potential for widespread clouds and early-day storms which could limit instability, but if we see enough breaks of sunshine the environment would certainly be favorable, once again, for one or more MCSs capable of damaging winds and torrential rainfall leading to localized flash flooding. At this time, SPC has areas west of I-65 outlooked in a level 2 of 5 (slight risk) for severe weather.

***** THURSDAY THROUGH MONDAY *****

Global deterministic models and their respective ensembles suggest ridging should build over the Midwest and Ohio Valley into the weekend, suggesting a downward trend in precipitation chances and continued warm, muggy conditions. However, particularly Thursday and Friday, we remain preciously close to the ring of fire - the northeast periphery of the ridge where the best overlap of instability and deep layer shear will favor MCS activity. Storm chances, around 40-50% northeast of a Jasper, Indiana to Somerset, Kentucky line Thursday into Friday, will finally drop below 20% by Saturday.

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 706 AM EDT Tue Aug 11 2026

A weakening ridge of high pressure should maintain VFR conditions at all of the airfields through mid afternoon. Scattered storms will develop over central/northern Indiana during the late afternoon and drop south into Kentucky during the evening into early overnight period. The highest confidence (50-60% chance) in storms will be at RGA and LEX, while chances taper to towards the south and west (less than 30% at BWG). While confidence is also low on timing, prob30 groups highlight the period of greatest concern at each terminal. Outside of storms, winds will blow out of the southwest, with gusts upwards of 20 kt at times during the afternoon.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Heat Advisory until 8 PM CDT this evening for KYZ023-026-061- 070>073. Flood Watch through Wednesday morning for KYZ032-033-035>037- 040>043-048-049-057. IN...Heat Advisory until 9 PM EDT /8 PM CDT/ this evening for INZ076-083-084-089. Flood Watch through Wednesday morning for INZ079.