textproduct: Louisville

KEY MESSAGES

* Multiple waves of showers and storms are forecast through this evening. There is a level 2 of 5 (slight) risk for severe weather, with damaging wind gusts and tornadoes the primary hazards.

* Areas that receive repeated rounds of heavy thunderstorms may see localized flooding. There is a level 2 of 4 (slight) risk for excessive rainfall.

* Daily shower and storm chances (30-50%) will continue into the middle of next work week, but the severe weather risk appears low after today.

UPDATE

Issued at 709 PM EDT Sat Aug 1 2026

Surface cold front has pushed through the I-65 corridor as of 700 pm EDT. A band of broken showers and storms will accompany the front as it continues eastward into the Bluegrass region this evening. Environment across the area remains slightly unstable, though low- mid level lapse rates remain rather anemic. Bulk shear values are up in the 30-35kt range between Louisville and Covington, and that band of shear will continue to lift off to the northeast through the evening. With temps in the upper 70s to lower 80s ahead of the front and dewpoints in the low-mid 70s, this is yielding MLCAPE values of 1000-1800 J/Kg. Winds are not all that backed ahead of the line. However, model soundings do show some low-level curvature which will continue to support organized convection with multi- cellular convection being the most prevalent convective mode. However, some transient supercellular structures will be possible over the next hour or so. With the setting sun, instability will continue to diminish through the evening. This line moving through the Bluegrass will produce brief heavy rainfall, gusty winds of 35- 40 mph, though a few gusts to 45 mph are possible, and lightning. With PWAT values up over 1.8 inches, the heavy rainfall threat is there. However, the progressive nature of the line will likely limit residence time of heavy rainfall over any one area. However, a quick 0.25 to 1 inch of rainfall can be expected with this activity. Some minor isolated flooding issues can't be ruled out.

SHORT TERM /THROUGH SUNDAY NIGHT/

Issued at 126 PM EDT Sat Aug 1 2026

***** SEVERE WEATHER, FLOODING RISK THIS AFTERNOON *****

Early Saturday afternoon, an area of low pressure was centered over east-central Illinois, with an occluded front draped southeast across central and southern Indiana and a trailing cold front extending all the way south into Texas and Louisiana. RAP mesoanalysis suggests that, where clouds have scattered out across areas mainly near and west of I-65, 500-1500 J/kg of MLCAPE has developed, and this should only increase as heating continues over the next couple hours. This, together with 30-45 kt effective bulk shear driven by the upper level low parked over southern Illinois, should prove sufficient to sustain storms that have developed across southwestern portions of the county warning area (CWA) early this afternoon. It's difficult to say for sure where the greatest severe weather/tornado risk will develop through the evening. Storm motion will be more south- north across northern portions of the area - which should offset the low level storm-relative shear driven by more backed surface winds there. Meanwhile, a more west-east storm motion will characterize cells that develop over southern/central portions of our area, which would offset the limiting effect of less backed surface winds on low level storm-relative shear. In both areas, N shaped hodographs suggest splitting storms with dominant right movers, which will make best use of the 100-200 m^2/s^2 effective SRH and pose the greatest landspout/tornado risk. Various ML guidance hits central/southern Indiana (near the triple point) with the highest potential for tornadoes, but some risk will exist with any right-moving storm across the area this afternoon and evening. Mid level dry air spilling in with the dry slot along/behind the broken line of storms may also drive some damaging wind risk, but with poor (mid and low level) lapse rates and mostly cellular storm mode, we don't think this will be a widespread issue; HREF doesn't seem to think so either, with only a couple very isolated pockets of gusts 45-55 mph in its ensemble max. The other concern will be potential for flash flooding, given an environment (PWAT >2 inches, >13 kft deep warm cloud layer) conducive to heavy rain-producers, and potential for repeated rounds of storms. HREF/REFS ensemble max have pockets of over 4 inches in 6 hours, which surpasses the 3-4 inch 6 hour Flash Flood Guidance (FFG) threshold. WPC maintains a level 2 of 4 (slight) risk for excessive rainfall east of roughly I-65, with a level 1 (marginal) risk further west. The time window of greatest risk for both severe weather (weak tornadoes, locally damaging wind gusts) and heavy rainfall (localized flash flooding) will be roughly 2-9pm EDT.

***** TONIGHT - SUNDAY *****

Rain chances diminish quickly from west to east late this evening, with many locations especially near and west of the I-65 corridor catching a glimpse of the sun before it sets. Dry weather will continue overnight, though patchy fog and drizzle could return early Sunday morning as wrap around moisture enters the area from the north. HREF seems to think we'll see breaks in this cloud cover by early-mid afternoon, but if that lingers longer (as it often does) we may stay quite a bit cooler than NBM; we knocked tomorrow's high temperatures down a couple degrees (from around 80 to mid-upper 70s) to account for this. Coverage (30-50%) will be lower compared to today, but beneath the upper level low, the combination of synoptic lift and weak diurnally driven instability should prove sufficient for a few showers and perhaps even a couple rumbles of thunder tomorrow afternoon and evening.

LONG TERM /MONDAY THROUGH SATURDAY/

Issued at 126 PM EDT Sat Aug 1 2026

***** MONDAY - SATURDAY *****

Slightly below normal temperatures, numerous clouds, and pop up afternoon showers are forecast to continue through at least Tuesday as the upper level cut-off low spins overhead. By Wednesday or Thursday, a northern stream wave should lift that pesky resident low into the Mid-Atlantic/Northeast, allowing a more seasonably humid and warm airmass to return to the region. Embedded within the relatively zonal flow regime will likely be one or more shortwaves capable of generating showers and storms (possibly severe), but predictability in terms of impacts and timing is low at this juncture. The forecast maintains slight (20-30%) chances for storms through next weekend while high temperatures, climbing a few degrees each day, reach the upper 80s to low 90s by Friday-Saturday.

AVIATION /00Z TAFS THROUGH 06Z MONDAY/

Issued at 709 PM EDT Sat Aug 1 2026

Surface cold front has passed through the KSDF/KBWG corridor. A line of convection remains along the frontal interface and will impact KLEX/KRGA around 02/00Z through 02/02Z. For KLEX/KRGA, we'll see heavy rainfall that may drop vsbys to 1/2SM with wind gusts of 25-30kts as the band pushes through. Once the line passes through, look for cigs to build back down into the MVFR range with drizzle/mist becoming prevalent during the overnight hours. Additional diurnally driven showers are expected through the day on Sunday as the surface and upper level move slowly across the region.

LMK WATCHES/WARNINGS/ADVISORIES

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