textproduct: Louisville

KEY MESSAGES

* Spotty showers continue early this morning, but severe weather is not expected.

* Heat and humidity begin to increase today, with temperatures nearing 90F and heat index values close to 100F.

* Max afternoon heat indices could be in the triple digits for some by early next week, but this remain conditional on any thunderstorm chances. A Heat Advisory may be needed for Monday and/or Tuesday.

* Rounds of strong to severe storms are possible starting early Monday and last through Tuesday. Pockets of wind damage will be the main threat, and the most likely time for severe weather is currently later Monday evening into Monday night.

SHORT TERM /THROUGH TONIGHT/

Issued at 257 AM EDT Sun Jul 26 2026

Overall, things are fairly quiet this morning however lots to consider in the near term. We're gonna hang onto some lingering pockets of drizzle and/or very light rain through the pre-dawn hours as 1000-800 mb moisture is slow to thin out. The bulk of the coverage will be across southern and eastern KY, but can't completely rule it out anywhere at this point. Look for some patches of fog through the morning also, but think it will mainly be a low stratus show.

Looking for things to trend mostly dry through the daylight hours as rather unremarkable NW flow aloft holds overhead. There was an upstream MCS over the upper Midwest that looked as though it could threaten our western CWA later this morning into early afternoon, however it has fallen apart of the past couple of hours. We'll have to watch to make sure any remnant outflow boundaries and/or a remnant weak MCV isn't able to trigger a new complex later this afternoon once we get strongly unstable, but right now most of the CAM data keeps things pretty quiet. Speaking of instability, HREF probabilities suggest pretty solid chances of 3000-4000 J/KG of SB CAPE along and west of I-65 by this afternoon. East of I-65, 1500- 2500 J/KG of CAPE is expected.

So, given the moderate to strong instability there is some concern that any thunderstorm that is able to get going could briefly become strong to severe. There does appear to be enough deep layer shear (30-40 knots of 0-6 km shear) thanks to a seasonably strong exit region of a mid to upper level jet nosing into the Ohio Valley region. These are the reasons SPC has place our area in a Marginal Risk for severe weather. However, the good news is that there really doesn't appear to be much of a trigger around today and this evening. We will have to watch for any upstream MCS activity to possibly dive into our area in the pre-dawn hours of Monday, but CAMs continue to be consistently inconsistent with their scenarios. Any convective complex that is able to make it into our area would carry a damaging wind threat with it. So bottom line, we'll be quite unstable today but lacking any notable triggers. Think we'll stay mostly dry and have to keep an eye on late tonight into Monday morning.

Assuming we don't get a bunch of convective activity today, the other main focus will be building heat and humidity. The eastern periphery of the upper ridge will become more established over the area today, and 1000-850mb thickness will rise. Looking for highs to reach into the 85 to 90 degree range today, along with increased dew points into the 70s. This is going to yield max afternoon heat indices in the upper 90s and low 100s along and west of I-65. Not quite enough concern for a Heat Advisory in our western CWA, but won't be too far from it. There is some concern that lingering stratus through the morning and plenty of upper sky cover from the upstream convective complex could keep temperatures in the underachieving range. Still, the humidity will see quite a notable jump so it is going to feel more muggy regardless.

LONG TERM /MONDAY THROUGH SATURDAY/

Issued at 257 AM EDT Sun Jul 26 2026

Monday - Tuesday Night...

Complicated early week forecast with multiple hazards possible, in addition to a temperature forecast that will be dependent on convective activity. We'll be situated in a NW flow aloft pattern on the eastern periphery of a strong western/central CONUS ridge through early week. This will put us in a strongly unstable airmass (SB CAPE over 3000 J/KG), and also in the presence of seasonably strong mid and upper level wind fields thanks to a persistent exit region of an upper level jet nosing into the Ohio River Valley. It is possible that a convective complex could be ongoing across the area on Monday morning, although confidence is lower than normal at this range as model data (including CAMs) have been inconsistent with this scenario. For now, let's assume a dry start to the day.

The first concern for Monday will be temperatures warming into the lower 90s in addition to dew points climbing well into the 70s for most, especially along and west of I-65. This would yield max heat indices in the 105-110F range along and west of I-65, and in the upper 90s and low 100s across our eastern third or so of the CWA. A Heat Advisory for half to two-thirds of our western CWA is likely in this scenario, although it comes with a caveat. The potential for the morning MCS and its convectively reinforced cold pool wrecking the temperature forecast, and/or an afternoon MCS diving into our area from upstream. As a result, won't be too quick to lift a headline until we are more confident in the convective evolution of upstream MCS potential. The same type of scenario also applies for Tuesday with similar values both in the T/Td department, maybe slightly less. So, we'll take a "wait and see" approach but will also continue to message the conditional heat/humidity threat to partners.

Back to the severe threats for Monday/Tuesday. Regardless of whether we get a Monday AM MCS, we do expect to become strongly unstable again by later Monday afternoon and evening. Forecast models continue to suggest upstream MCS activity gets going, and then has a good chance of diving into our area. The combination of 700-300 mb mean wind fields combined with any notable instability gradients are usually pretty good at steering these cold pool driven / forward propagating MCS's. As a result, do think we'll see impacts from at least 1, if not multiple thunderstorm complexes Monday and Tuesday. Given the amount of instability, deep layer shear (especially mid to upper level speed shear), and the likelihood of additional help from a developed cold pool from upstream activity think the main concern will be damaging winds. Perhaps a widespread damaging wind threat could develop if things really get going. Most likely locations for this would be across our NE CWA. Prolific lighting, and some potential for localized heavy rainfall may also develop. These systems usually tend to be progressive, however will have to watch for some training potential where the western flank of any MCS gets left behind by the surging cold pool. Will still be tons of instability in these areas, but will be oriented more parallel to the mean deep layer flow and could overachieve on rainfall. Right now, the most consistent signal for an impactful MCS would be later Monday evening into Monday night. Like the idea of SPC messaging the severe risk, albeit it is still conditional upon storm track.

Wednesday - Friday...

The mid to late week time frame looks fairly quiet as we remain in NW flow aloft, but this flow will be rather unremarkable with respect to any triggering shortwave features. In addition, surface high pressure builds in behind the departing cool front associated with the late Monday/early Tuesday system passing through the Great Lakes. The end result should be a mostly dry forecast with temperatures settling back around normal for this time of year in the upper 80s.

Saturday...

Quite a bit of uncertainty by early next weekend. It appears a stronger shortwave may round the top of the upper ridge and try to dig into the mid Mississippi River Valley. This could be a trigger for scattered showers and storms by Saturday. Quite a bit of complex upper pattern evolution before we get to that point, so will keep this low confidence for now. Temps should generally be around normal for this time of year, still in the upper 80s.

AVIATION /06Z TAFS THROUGH 12Z MONDAY/

Issued at 127 AM EDT Sun Jul 26 2026

RGA/BWG are the most likely sites to experience some drizzle and vis reduction through the early morning hours. These will be in addition to MVFR/IFR ceilings. The low ceilings are expected for all TAF sites, and have put the expected timing for category jumps in there. Surface winds will be light and variable for much of the morning before eventually finding a more steady W-E component around midday through the afternoon. Expect a return to VFR also by late morning to midday. Shower and storm coverage confidence is low for later tonight, and not quite ready to put in any Prob30 mentions just yet.

LMK WATCHES/WARNINGS/ADVISORIES

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