textproduct: Louisville

KEY MESSAGES

* Scattered storms this afternoon followed by a more prominent line of storms this evening will bring heavy downpours and severe potential for severe wind gusts and small hail. Southern IN counties and KY counties that border the Ohio have the best potential.

* There is flooding potential for the storms that move through tonight, especially in our southern IN counties.

* Another surge of moisture moves in by Wednesday morning, keeping clouds and rain for everyone and scattered storms for eastern locations by the afternoon.

* Busy weather pattern sets up Wednesday through the remainder of the week, with widespread moderate rainfall expected Friday.

UPDATE

Issued at 905 PM EDT Tue May 19 2026

With the loss of daytime heating much of the afternoon activity has either moved our or dissipated. A few more isolated to scattered areas of showers and storms are likely to develop before a second wave of activity is expected late tonight into early tomorrow morning. Sfc boundary will continue to approach from the northwest as activity currently over Arkansas along with a midlevel shortwave will surge into the area with additional shower and thunderstorms. Severe threat with this activity appears low but our attention turns to flooding concern, especially acrosss southern IN where they are saturated from last night's event.

Only adjustments in the grid was to account for this slight lull in activity before the next wave begins late tonight and tomorrow morning. The rest of the forecast remains on track.

SHORT TERM /THROUGH THURSDAY/

Issued at 344 PM EDT Tue May 19 2026

Currently, temperatures are warm in the mid to upper 80s with mixed cloud cover area wide. A few communities have already seen rain today from two axis of showers and storms trying to form in our western and eastern counties. The severe threat for strong to severe gusty winds aren't expected from these ongoing storms, at least not until later this evening from an approaching line of storms from the northwest. However, what is popping up on radar still has the potential for some small hail stones and gusty winds before the main event arrives.

The synoptic setup features troughing in the Plains with continued ridging in the east. The overall weather pattern though will be changing as early as tonight as a trailing cold front from a surface low up in southern Canada will move across the Ohio Valley this evening through Wednesday afternoon. This front is very slow, and will help initiate a line of storms across the Midwest that will move into our CWA this evening.

This more prominent line of storms, preceded by pop up storms ahead of the main line, will move in from the northwest well ahead of the cold front. There is plenty of SBCAPE for this line to tap into however as they approach and develop near our CWA, the best shear will move north into the Great Lakes and Southern Canada. Once evening sits in as the storms move in, this means they will slowly be weakening as they trek across our counties. Despite this, multi- cell clusters forming into bowing line segments are possible bringing severe to strong gusty winds and small hail if some of the storms could grow tall enough. With CAPE values ranging 2500 - 3000 J/kg or higher this afternoon in southern IN and western KY, hail can't be ruled out. The highest severe threat is in southern IN and into KY counties bordering the Ohio.

Additionally, PWAT values are running high ranging 1.5-2", favored in southern IN thanks to a surge of moisture from the SW. Dewpoints will be running high, meaning there is potential for additional flooding this afternoon/evening in the same areas that were hit hard last night, namely southern IN. As a result, a flood watch has been issued for all our southern Indiana counties including Trimble County as well. Our western KY counties are under the same SW plume of moisture too and will be monitored for flooding potential. Should more rain trend to fall in this area, the flood watch may need to be expanded. Rainfall totals are greatest in southern IN, western KY counties, and counties along the Ohio have a 70-80% chance of receiving ranging around 0.5 - 1", with localized areas of 2+" according to HREF LPMM data in training storms. Elsewhere in central/southern KY including cities like Lexington, rainfall totals will generally by around 0.25-0.5" or lower by early Wednesday morning.

Temperatures will cool this evening into the 60s and 70s with weak winds and lowering cloud heights. Rain showers and embedded thunderstorms will continue tonight with spotty coverage until a weak developing low pushes up from Arkansas Wednesday morning following along our slow-moving cold front. This will keep a steady supply of moisture for everyone Wednesday morning. A few weak embedded storms and rumbles of thunder are possible then, especially in our far southeastern counties that may partially clear. Later in the afternoon with partial clearing, continued WAA in the east, and CAPE values nearing 1000+ J/kg, some gusty winds may be possible with a few of these storms, though we are not expecting severe weather with Wednesday's convection at this time. This may build up enough instability for a few storms to produce more lightning . As the developing surface low slowly moves east, so will any rain showers and weak storms exit to the east. Highs on Wednesday will vary generally northwest to southeast tomorrow as clouds and the cold front slowly marches eastward. Along and north of the Ohio, highs will be in the low to mid 70s with upper 70s to low 80s in our southeast border counties. Rain showers and storms end Wednesday night with lows in the mid 50s to low 60s.

LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/

Issued at 344 PM EDT Tue May 19 2026

Thursday's weather seems a little drier compared to Wednesday as the cold front should clear or nearly clear our southern communities by morning. Since this front is stalling so close by, continued rain showers with low PoPs have been continued for our far southern areas, though rain totals look to remain low. Cloud cover remains throughout the day though, limiting our warming Thursday behind the front with highs in the low to upper 70s in a few places.

By Friday, a trough exiting on the leeward side of the Rockies in the Mid-Plains will swing our front back north as a warm front with a returning surge of moisture from the southwest. EFI tables suggest a moderately high EFI values for QPF, meaning this incoming surge of moisture could produce a good amount of rain for drought stricken areas across all of the CWA. 25th and 75th percentile rainfall totals range from near 0.5" to 1" of rain during the day on Friday. Timing of this rainfall and when it ends is a little uncertain still, as it appears once Friday's trough clears, there is not much synoptic forcing to sweep the front out of the area. As a result, rain chances could continue into Saturday, further alluded to by moderately high EFI values for QPF Saturday. There is still high uncertainty with rain chances later in the weekend though as LREF clustering analysis shows high spread in the rainfall totals. Should another stalled out front form over KY, more rain is likely, but if the stalled out front moves well to our south, Sunday and early next week will begin dry. Temperature trends this weekend remain warm in the upper 70s to low 80s for highs.

AVIATION /06Z TAFS THROUGH 12Z THURSDAY/

Issued at 110 AM EDT Wed May 20 2026

For the remainder of the overnight period, conditions will start off as VFR at the terminals with ceilings gradually lowering toward dawn. Scattered convection will be possible, mainly west of a line from BWG to HNB. Surface cold front will push through the region after dawn which will allow winds to shift to the northwest. As we move into the late morning hours, an upper level perturbation will move northeast along the sagging front which will kick off additional showers/storms, mainly east of a line from BWG to LEX. Cigs will likely drop into the IFR range with MVFR vsbys due to rain/storms. Convective activity will push off to the east toward the end of the period with IFR cigs remaining in place.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Flood Watch through this afternoon for KYZ032. IN...Flood Watch through this afternoon for INZ076>079-083-084- 089>092.