textproduct: Louisville

KEY MESSAGES

* Waves of showers and thunderstorms are expected Tuesday into Wednesday, bringing widespread beneficial rainfall to the area. Widespread rain totals of 1-2" are likely, with localized heavier totals possibly leading to a few instances of high water or minor flooding.

* High temperatures look to warm back into the 70s this weekend, with isolated to scattered rain showers.

SHORT TERM /THROUGH TUESDAY NIGHT/

Issued at 344 PM EDT Mon May 4 2026

This afternoon, mostly sunny skies are noted on satellite imagery with a mixture of lingering high clouds and a few stratocu where sfc dewpoints have crept up into the mid-to-upper 50s. Temperatures are warm across the area, with latest obs ranging from the mid-70s to around 80 degrees. We should be able to add 1-3 more degrees this afternoon, reaching highs in the upper 70s and low 80s. The sunshine has allowed for relatively deep mixing to occur, with latest SDF ACARS soundings showing the PBL mixing to around 875 mb. This has allowed 20-30 mph wind gusts to make it down to the surface, and gusty winds should continue through early this evening when typical nocturnal decoupling begins.

The current synoptic pattern across North America features a disjointed series of upper lows/troughs, with a broader upper low across Ontario and a secondary cutoff upper low extending across CA/NV. These features are reflected at the sfc as an elongated cold front which extends from the southern Plains across the mid-Miss. Valley and into southern Ontario this afternoon. Over the next 24-48 hours, a shortwave on the western flank of the upper low over Canada will assist in ejecting energy from the cutoff low over the western US across the southern Plains and toward the Ohio Valley. This will help to nudge the sfc cold front gradually through the area by Wednesday evening. Between now and then, low-level response to the ejecting energy aloft will draw moisture northward from the Gulf, bringing rounds of showers and storms to central KY and southern IN, beginning Tuesday and continuing through much of the mid-week period.

Tonight, convection firing from eastern MO over to central IN may approach our southern IN counties, especially after midnight. However, as showers and storms approach the area, increasingly dry air between the sfc and 700 mb should lead to a weakening in any precipitation. Still, we'll carry a 20-30% PoP for areas north of the Ohio River late tonight, with precipitation amounts mainly less than 0.10". Otherwise, increasing south-southwest flow aloft should translate down to the surface as a persistent 5-15 mph southerly breeze, helping to keep temperatures considerably milder than previous nights. Most locations should drop into the mid-to-upper 50s early Tuesday morning, with temperatures remaining fairly steady as clouds increase from the northwest early Tuesday.

During the day on Tuesday, southwesterly flow at 850 mb should strengthen from around 35-40 kt in the morning to 45-50 kt Tuesday night. This persistent flow regime will draw Gulf moisture northward, with HREF PWATs exceeding the 90th percentile of climatology (1.4-1.6") by Wednesday morning. Ongoing convection over the Ozarks tomorrow morning should move into the areas west of I-65 just before lunchtime, with HREF paintball plots of >30 dBZ increasing from west to east across the area from late morning through the afternoon hours. Since this activity will be on the leading edge of the greatest moisture axis, it will likely dissipate somewhat as it moves east, and precipitation chances will remain lower until later tomorrow afternoon and evening along and east of US 127.

From the middle of Tuesday afternoon through the end of the short term forecast period Wednesday morning, additional waves of showers and embedded thunderstorms are expected to slide from west to east across the region as the strengthening moist S/SW flow aloft lifts up and over the southeastward-moving sfc cold front. The amount of coverage of thunderstorms is a bit uncertain, but should generally decrease the farther NE you go as HREF MUCAPE progs show the sector of non-zero CAPE diminishing. By late Tuesday night into Wednesday morning, the sfc cold front should begin to cross the area. One thing we'll have to watch is if the sfc front is slower to push to the south, there would be more time for greater low-level moisture to sneak into south central KY. Right now, most model soundings show convection remaining elevated with minimal SBCAPE making it into the area given deep saturation through the column. If convection were to become surface-based, ample curvature in hodographs along with a strong llvl wind field would support a conditional severe threat across our southwestern counties; however, this is low confidence at this time.

For rainfall totals through Wednesday morning, the heaviest rainfall amounts should fall along and north of the Kentucky Parkways, though areas south of the Parkways will see better chances of rain during the day on Wednesday (see below). 24-hr QPF LPMM from the HREF shows the higher end potential with any training convection with swaths of 2-3, even 4" of rain possible, with the best chances for this occurring west of I-65 and near the Ohio River. While these heaviest amounts could lead to local high water issues, antecedent dry conditions and the relatively lengthy period of time over which this rain should fall should limit the overall flooding threat.

LONG TERM /WEDNESDAY THROUGH MONDAY/

Issued at 344 PM EDT Mon May 4 2026

The above mentioned cold front will continue to move SE through the Ohio Valley with persisting rain showers through the day Wednesday. The cold front is expected to make its way out of the Bluegrass and Lake Cumberland region between 15-18z. Rain chances will gradually decrease NW to SE moving out of western KY as showers linger behind the front. QPF amounts between 1-2 inches are expected across the region with this system. Temperatures will only warm to the low to mid 60s across the area with nighttime lows in the mid 40s. Other than slight chances (<20%) for scattered rain showers Thursday, majority of the area should stay dry as surface high pressure moves in behind the cold front.

Skies will start to clear Thursday afternoon/ evening with this region of sinking air. Friday's temperatures are expected to warm back into the 70s with mostly clear skies. Another low-level shortwave will bring the rain chances back Friday evening. Light rain showers will mostly move through southern IN and the Bluegrass region overnight Friday into Saturday morning. Due to drier air aloft, QPF amounts are minimal for these scattered showers. Winds have a potential to become gusty around 30mph as these showers move in Friday evening.

Multiple shortwaves will keep isolated to scattered showers in the forecast for most of the weekend. A moisture transport axis will stretch across the Ohio Valley Sunday afternoon as another boundary approaches with rain and possible thunderstorms. This could be another chance for some healthy rainfall totals if ample moisture can make its way in from the SW. Guidance currently reveals an area of 1000 - 1500 J/kg SBCAPE Sunday evening, however a very marginal shear profile. Therefore, at this time no major severe threats are expected. There is low confidence with this event due to it being 6 days out still.

AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/

Issued at 751 PM EDT Mon May 4 2026

VFR are ongoing and will continue through the overnight and into Tuesday until midday. SW winds with gusts of up to 25 kts will slowly be calming throughout the night with BKN high level cloud cover sticking around with partial clearing at times. At 03Z, a low- level wind shear will be moving in from the west but will be weakening as it progresses eastward, with LEX-RGA enduring the shortest amount of time with WS. SW winds gusts reach 15-25 kts again by mid-morning ahead of a slowly approaching cold front bringing in rounds of rainfall by midday in the west and later in the afternoon east of SDF. Ceilings will be dropping as the rain approaches with MVFR conditions expected at SDF dropping to IFR in HNB towards the end of the TAF period. With rain and lower ceilings lingering into Wednesday, MVFR or lower conditions will continue at HNB-SDF.

LMK WATCHES/WARNINGS/ADVISORIES

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