textproduct: Louisville

KEY MESSAGES

* Isolated showers and storms are possible today, mainly across southern Indiana and southern Kentucky. Central Kentucky should stay warm and dry.

* Unsettled weather with localized areas of heavy rainfall and flash flooding are possible in KY and southern IN Monday - Tuesday midday. Localized amounts of 3-6" of rain will be possible in the heaviest swaths.

* Hot and humid Wednesday and Thursday, with peak afternoon heat index values between 90-100.

* Additional showers and thunderstorms possible in the medium range, especially Wednesday morning and again Thursday evening into Friday. Some strong storms and locally heavy rainfall will be possible.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 339 PM EDT Sun Jun 7 2026

This Evening and This Evening...

Warm and humid conditions are present across the region this afternoon, with temperatures mainly in the mid 80s across the area. Dewpoint temperatures range are in the upper 60s and low 70s across two separate areas: one generally north of I-64 and another one along the KY/TN border. There is a relative minimum in near-sfc moisture across the middle of the CWA. Variations in sfc heating and humidity can be seen in satellite imagery based on the amount of cumulus present. Just to the north of the area, this diurnal convection has combined with enough residual convergence along a washed out front for showers and a few storms to develop. Through the mid-evening hours tonight, an isolated shower, possibly a storm may be able to form north of I-64 and along the KY/TN border where there is better moisture; however, most areas should remain dry through early Monday morning. Temperatures are expected to top out in the mid-to-upper 80s before dropping slowly through the 80s and into the 70s tonight.

Late Tonight through Monday Night...

Late tonight into Monday morning, a corridor of slightly stronger low-to-mid level SW flow is expected to lift from SW to NE across the lower Ohio Valley, bringing a surge of greater moisture with it. This will be associated with a mid-level shortwave disturbance that is expected to move from the southern Plains today across the mid- Miss. Valley on Monday and into the lower Great Lakes by Tuesday. The surge of moisture which is expected to move across the area with this system is quite anomalous, with precipitable water values expected to exceed 2", or roughly the 99th percentile of model climatology, Monday into Monday night. This surge of moisture should initially manifest as increasing clouds, but by Monday morning, scattered showers and storms are expected to lift in waves from SW to NE across central KY and southern IN. As has been mentioned over several discussions, sounding profiles are quite favorable for efficient heavy rain production, with HREF mean instability amounts of 1000-1500 J/kg spread across a deep layer. With the upper ridge axis close to the area, cloud layer winds are expected to be modest, on the order of 15 mph, resulting in relatively slow storm motions.

The combination of ingredients referenced above should support swaths of moderate to heavy rainfall amounts Monday afternoon and evening, with basin average amounts of 1 to 2.5" likely, especially across the western two-thirds of the CWA. What is of greater concern is the potential for isolated higher totals, with the 12Z HREF showing 6-hr LPMM rainfall swaths of 3-6" across portions of the area. These amounts, if realized, would lead to flash flooding, as exhibited in the WPC Day 2 Excessive Rainfall Outlook. At the same time, the coverage of these heavier swaths is still uncertain, and because of this, while a Flood Watch may be needed for portions of the area, we will hold off on headlines for now.

With scattered to numerous showers and storms in the forecast, it is also important to mention that while lightning and gusty winds will be possible in stronger convective cores, organized severe weather still appears to be unlikely Monday afternoon and evening as deep- layer shear should be fairly weak (generally 15 kt or less).

Showers and storms should diminish in coverage after sunset Monday, with most areas remaining dry into Tuesday morning. However, a secondary wave of showers and storms is progged to develop in some hi-res outputs early Tuesday morning as another 20-25 kt LLJ noses into the region from southern IL.

Temperature ranges Monday into Monday night should be suppressed due to ample moisture, with highs only expected in the upper 70s and low 80s, and lows only falling into the upper 60s and low 70s.

Tuesday and Tuesday Night...

By Tuesday morning, the main mid- and upper-level shortwave axis is expected to be lifting across Michigan and the Great Lakes, with a new upper ridge axis developing over the southern Plains and Mississippi Valley. With showers and storms potentially ongoing Tuesday morning across portions of the area, many aspects of Tuesday's forecast are uncertain. The general trend should be toward less shower/storm activity as we get later into the day on Tuesday and into Tuesday night due to the gradual loss of better synoptic forcing aloft. However, the residual air mass with ample low-level moisture would support additional shower/storm development depending on mesoscale features such as differential heating boundaries or convective outflow boundaries which will be difficult to resolve more than 6-12 hours out. As a result, we'll keep high PoPs (80-90%) in the forecast into Tuesday. Temperatures similar, if not slightly warmer than persistence during the day on Tuesday, with highs most likely in the low-to-mid 80s.

While the overall risk for severe weather is not particularly concerning Tuesday into Tuesday night, AI/ML guidance does show a signal for some severe convection, particularly Tuesday night, with a setup that could be favorable. With the lower Ohio Valley expected to be on the NE side of an emerging ridge, with a pool of higher instability located to the northwest of the region, it is possible that we could get an MCS to drop from NW to SE into the area, with several deterministic models showing a signal for this Tuesday night into Wednesday morning. While confidence in this occurring is still low-to-medium, if this occurred, there would be a damaging wind potential for our area. For now, we'll continue to monitor this potential, with hi-res guidance over the next 24-48 hours hopefully adding confidence in whether or not this may occur.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Issued at 339 PM EDT Sun Jun 7 2026

Wednesday - Wednesday Night...

We start off the medium range with a warm, moist airmass in place: mean PW values near 1.8 inches and sfc dewpoints in the low to mid 70s. A mid and upper level ridge centered over Mexico and Texas will extend northeast over the Lower MS Valley, nosing east over the TN and Lower OH Valleys. The latest 12Z deterministic GFS/ECMWF seem to hint at possible MCS activity riding the mid-level ridge axis before dropping southeast from central IL/IN Tuesday night into Wednesday morning. So it's possible we may have some convection ongoing Wednesday morning, but forecast confidence remains lower on the detailed evolution of any convection that far out. However, a majority of LREF members (70%) support the idea of some accumulating rainfall Wednesday morning.

Mid-level subsidence, especially in the wake of any morning showers/storms, would likely lead to drier conditions later in the afternoon and evening. Ensemble mean guidance points to a minimum in precipitable water Wednesday night into early Thursday (1.6-1.7 inches). And with a lack of forcing, Wednesday night should remain dry.

The only other concern on Wednesday will be very warm and uncomfortably humid conditions. 850 mb temperatures are forecast to rise to 19-20 C by Wednesday and Thursday, which is around the climatological 98th percentile. If conditions indeed mostly dry out during the second half of Wednesday, temperatures will likely top out in the mid 80s to around 90. Low to mid 70s dewpoints will contribute to heat indices peaking between 90-100 Wednesday afternoon and evening. Sfc temperatures will only fall into the lower 70s for lows Wednesday night.

Thursday - Friday...

A potent upper level trough and mid-level vorticity maximum are forecast to rotate northeast over the Upper Midwest and Great Lakes Thursday into Friday. This system should feature a parent sfc cyclone near Hudson Bay, with secondary cyclogenesis likely from the Great Lakes into portions of eastern Canada. Very warm, moist low- level SW flow will remain in place ahead of a cold front dropping through the Midwest. It appears we could see some spotty convection in the warm sector on Thursday, but otherwise we can expect a hot and humid day with highs in the upper 80s and lower 90s. Peak heat index values look to reach the mid 90s to low 100s Thursday afternoon and evening.

The potential for showers and thunderstorms will likely be maximized along the cold front Thursday night into Friday. Medium range AI severe convective guidance suggests some potential for strong storms 12Z Thu - 12Z Fri, with higher probabilities (15+ percent) east of our area after 12Z Friday. Overall, the severe weather signal is relatively modest and this may be partly due to an ill-timed cold front late Thursday night or early Friday. We will have some potential for locally torrential rainfall, gusty winds, and lightning, however. Forecast confidence is considerably lower beyond Friday.

AVIATION /00Z TAFS THROUGH 06Z TUESDAY/

Issued at 755 PM EDT Sun Jun 7 2026

VFR conditions to start this forecast period, but expect conditions to deteriorate to low-end MVFR and IFR after 09Z Monday. Rich moisture will surge in from the south just ahead of a mid-level shortwave trough lifting northeast over the Midwest. Numerous SHRA and scattered TSRA will develop across the region Monday morning and afternoon. Light SSE winds of 5 kts or less are expected overnight, increasing to 5-10 kts Monday afternoon.

LMK WATCHES/WARNINGS/ADVISORIES

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