textproduct: Louisville

KEY MESSAGES

* Light showers and perhaps a few elevated storms are possible Sunday night into Monday morning. Gusty southwest winds expected Monday, with temperatures returning to the upper 70s and near 80.

* Most Active Period: Tues-Wed Night with widespread 1-2" of beneficial rainfall from widespread showers and storms.

UPDATE

Issued at 910 PM EDT Sun May 3 2026

Conditions are mostly clear this evening with temperatures now in the mid 50s to lower 60s. A mid-level shortwave trough is producing a narrow band of clouds stretching ESE across central IL/IN and northern KY. As this wave moves southeast tonight, a 35-40 kt WSW LLJ will develop over the Lower Ohio Valley. 30 kt SW low-level flow is already producing notable WAA over portions of IL/IN/KY. Regional radar shows a thin, broken band of showers stretching across the southern half of IL/IN. Scattered showers will develop further southeast into portions of southern IN and north-central KY after 03- 04Z tonight as the LLJ strengthens and the moisture axis dips southeast.

Additional upstream convection is likely to develop tonight from central MO into IL. A secondary, stronger SW LLJ will stream northeast from KS into a stalled boundary near central MO. This activity should then translate ESE across southern IN and portions of north-central KY through the early to mid-morning hours of Monday. This should be in the form of a band of broken rain showers, though isolated embedded storms are possible during the early morning hours. MUCAPE increases to 200-500 J/kg, with decent lapse rates aloft. However, any isolated storms will be elevated with SDF ACARS soundings already showing a pronounced inversion near 800 mb.

Rainfall amounts of 0.10-0.25 inches look possible northeast of a line from Jasper IN to Richmond KY. Very narrow, localized swaths of more than 0.50" are possible due to training showers.

SHORT TERM /THROUGH MONDAY NIGHT/

Issued at 243 PM EDT Sun May 3 2026

A region of surface high pressure is over the Ohio Valley currently, giving dry, clear skies and mid-upper 60s across the area. Rain chances will however return tonight across the area. A mid-level shortwave will move across the region placing a LLJ over the Ohio Valley. This forcing will develop isolated to scattered rain showers over central IL and move SE into the area by 05z. As these showers move in there is a chance (20%) for some thunder, but a nighttime capping inversion will eliminate any severe potential.

The majority of precip will move out of the area by tomorrow morning/early afternoon. Other than some light rain showers in southern IN through the day, tomorrow should remain mostly dry. Temperatures will warm in the upper 70s tomorrow as SW flow brings a WAA zone over the area. Winds tomorrow will be slightly higher with some afternoon gusts near 30mph.

As a low pressure system builds over Ontario, broad upper level troughing moves overhead. This system will favor a cold front that will stretch NE from the central Plains to the Great Lakes, positioning us in the warm sector by Tuesday morning. Low level moisture advection from the Gulf will be supported by the SW flow, bringing a moisture band over the Ohio Valley. Widespread rain chances will begin overnight Monday, with lows staying in the upper 50s.

LONG TERM /TUESDAY THROUGH SUNDAY/

Issued at 243 PM EDT Sun May 3 2026

===== Tuesday through Wednesday Night ======

Synoptic Setup: Broad upper-level troughing will dominate the eastern two-thirds of the CONUS as a closed upper-low meanders over the Hudson Bay. This setup establishes a deep southwesterly flow, advecting rich gulf moisture into the Ohio Valley ahead of a sfc cold front during the day Tuesday. A weak sfc low will develop along the boundary over the Plains then ride along the cold front into the Ohio Valley Tuesday night. This will strengthen the LLJ over the area and provide amble forcing for widespread rain and thunderstorms. Despite having robust sheer associated with the LLJ, meager instability will limit the threat of strong to severe storms. Main potential impact would be some gusty showers if some of the heavier showers/storms tap into the LLJ and bring it to the surface.

Current QPF forecast by Thursday morning generally falls in the 1-2" range. Moisture axis ahead of the approaching cold front will increase PWAT values to around 170 percent of normal to 1.50". WPC places the area in a Marginal risk (Level 1/4) both Tuesday and Wednesday for excessive rainfall. Given the current D1-D3 drought conditions across the Commonwealth of KY and 48-hour duration of the event, the threat of flash flooding and other hydrological concerns remain low. The rainfall will be mostly beneficial.

Probabilistic guidance adds confidence to the current rainfall forecast as there is strong consistency between the NBM, the LREF and ECMWF ensembles with all having about a 60-75 percent probability of getting greater than 1 inch of rainfall and around a 10-20 percent probability of exceeding 2 inches.

===== Thursday - Next Weekend =====

The pattern remains unsettled but with lower forecast confidence. The Ohio Valley remains under the influence of the Hudson Bay upper- low, with a couple of shortwaves rotating through the base of the trough. Confidence is low regarding moisture return behind the front. For now, have maintained a drier forecast for Thursday/Friday in the grids. With a few more spokes of energy working along the base of the upper-level trough for the weekend, periodic rain chances can't be ruled out but it doesn't look like a washout.

Temperatures will generally be near to slightly below seasonal normals through the long term forecast.

AVIATION /00Z TAFS THROUGH 06Z TUESDAY/

Issued at 817 PM EDT Sun May 3 2026

VFR weather is likely through much of this TAF period, although brief MVFR vis in moderate showers will be possible overnight. A mid- level wave moving over the region will bring scattered SHRA and isolated TSRA to southern IN and north-central KY between 03-13Z Monday. Confidence in thunder is too low to include in the TAF at this time, but we did go ahead and include slightly lower vis in PROB30 groups. Ceilings look to dip as low as 6-9 kft for a relatively short period of time between 05-12Z.

Steady southerly winds of 5-10 kts expected overnight, but marginal LLWS conditions will develop during the early morning hours with the arrival of a 35-40 kt SW LLJ. Expect a breezy Monday with wind gusts increasing to 20-25+ kts after 15Z.

LMK WATCHES/WARNINGS/ADVISORIES

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