textproduct: Louisville

KEY MESSAGES

* Remnant showers this evening will become spotty in southern areas with temperatures hovering in the mid 50s to low 60s.

* Warm front moves north through the area, bringing widespread rain Friday morning. Building instability will create a marginal risk for severe gusty winds, a small chance of a tornado, and a flash flood threat with heavy downpours.

* Scattered lighter rainfall is expected on Saturday. Additional waves of showers and storms will be possible Sunday into the middle of next week. Localized excessive rainfall may result in flooding.

SHORT TERM /THROUGH FRIDAY NIGHT/

Issued at 347 PM EDT Thu May 21 2026

Remnant showers with light to moderate rain remains in east-central KY where some decent rain totals have fallen. High temperatures underperformed from a cool NE flow and continued cloud/rain coverage today. PWAT values remained high enough with continual moisture transport to keep most places socked in with moisture and low clouds. A few southern border counties warmed into the low to mid 70s since they were further away from the best lift of the incoming front. As the evening progresses, this trailing cold front will gradually push the moisture towards the southeastern CWA border this evening and tonight. Temperatures overnight will remain in the mid 50s to low 60s. There could still be some rain chances along our southern border overnight, though any rain to fall will be light, generally in the form of sprinkles, though low-end PoPs continue overnight for those areas.

By Friday morning, the synoptic weather pattern shifts as a negatively tilted trough swings through the northern Plains. This trough will help form a new surface low swinging in from the Gulf states, bringing in widespread rainfall in the morning ahead of an incoming warm front. Light to moderate, and sometimes heavy rainfall is expected with this swath of stratiform rain moving in, further helping to relieve drought conditions.

However, by early afternoon Friday, the newly formed surface low will induce a low to mid-level jet over central KY. With plenty of moisture streaming in from the SW, PWAT values will be high in the 1.5 - 2" range in the afternoon. Additionally, after the initial swath of rain moves to our NE, cloud cover may begin to break, allowing additional daytime heating to occur across south/central KY. So with plenty of moisture, 30 kt surface to 500 mb shear, and increasing instability Friday afternoon, there is potential for clusters of storms or supercells to form becoming severe in the afternoon. SPC has issued a marginal risk for severe weather, and with current CAPE values and model lapse rates, the severe risk is from strong to severe gusty winds along with a small chance of a tornado. As storms roll in from the south and west, there will be plenty of moisture to work with, creating a flash flood threat for storms or heavy rain that trains over the same areas. 6hr LPMM data from the latest HREF run indicates localized areas of 2-4+" inches are possible in training storms. This flooding threat will be monitored as the event progresses and may need to issue a Flood Watch in our CWA, especially considering the amount of rain our central/southern communities have seen today. Temperatures will be warm tomorrow afternoon, with highs in the low to upper 70s. As Friday evening approaches, storms lingering in the area will weaken with the loss of daytime heating, and the severe threat will end just after sunset.

LONG TERM /SATURDAY THROUGH THURSDAY/

Issued at 347 PM EDT Thu May 21 2026

A mid-level shortwave trough and associated sfc low will continue northeast across Indiana Friday night. Deep-layer SW flow continues with PW values remaining in the 1.6-1.8 inch range. Numerous showers and scattered thunderstorms will likely be ongoing at the start of this forecast period 00Z Saturday. Convective intensity should gradually wane overnight due to decreasing instability, with thunderstorms more isolated in nature by the early morning hours of Saturday.

The wave of low pressure continues off to the northeast across the Great Lakes Saturday and Saturday night, taking the stronger forcing and deeper moisture with it. This will result in scattered, lighter intensity showers on Saturday, with rain chances gradually decreasing from west to east Saturday afternoon and evening. Most places should be able to briefly dry out Saturday evening and overnight. Lows in the low 60s will be common, with Saturday afternoon highs in the mid/upper 70s.

By Sunday, an upper level trough develops over Texas with a deeper wave swinging northeast across Ontario and the Upper Midwest. Overall forcing isn't all that strong, but we will still have a moist low-level airmass in place with weak convergence along a remnant boundary. Scattered storms appear possible Sunday, especially in the afternoon and evening hours as the moist airmass destabilizes. Forecast confidence in the detailed evolution is low, but the overall threat for organized severe convection looks low due to weak shear. Localized heavy rainfall is possible in slow-moving showers and storms.

A mid/upper level low slowly meanders north over the southern Plains through early next week, with downstream confluent flow over the Ohio Valley. A quasi-stationary sfc boundary with deep moisture (PW values 1.5-1.75 inches) pooled along it will very slowly drift northward over the TN and Lower OH Valleys. This will bring additional showers and thunderstorms to the region, and the rainfall could be heavy at times with at least an isolated risk for flooding.

AVIATION /18Z TAFS THROUGH 00Z SATURDAY/

Issued at 154 PM EDT Thu May 21 2026

IFR-Low end MVFR conditions will continue into the evening and overnight hours. Light to moderate rain showers in the east will end over the next few hours though ceilings will struggle to improve across the area. Occasional high-end MVFR to low-end VFR conditions could return to HNB-SDF overnight before they lower again after sunrise. Otherwise, light NE winds will persist into tomorrow morning, with ceilings remaining low between IFR-MVFR conditions through Friday. In the morning, winds begin to shift out of the E to SE with a wide swath of light to moderate rain for all airports moving in from the southwest. If ceilings improve in the morning, they will lower once again with the widespread incoming rain on Friday, which will become more scattered and mixed with storms in the afternoon. LEX/RGA may dip into LIFR conditions with the current ceiling forecast in the morning into the afternoon as well. Otherwise, MVFR to IFR conditions are expected for everyone Friday afternoon.

LMK WATCHES/WARNINGS/ADVISORIES

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