textproduct: Louisville

KEY MESSAGES

* Scattered storms return this afternoon along an axis of a shortwave bringing heavy downpours, lightning, and potentially damaging wind gusts in areas east of I-65.

* Rainfall totals of 0.25-0.75" from widespread storms this afternoon are expected with localized 3+" possible, bringing a localized flash flooding threat.

* A line of storms bringing potentially damaging wind gusts especially across eastern-southern IN moves in Saturday evening near 7-9 PM that will slow down and weaken across central KY overnight into Sunday.

SHORT TERM /THROUGH SATURDAY/

Issued at 337 AM EDT Fri Jul 17 2026

===== Friday - Saturday =====

Despite a lone shower in Clark County, KY, conditions are quiet with clearing skies. Friday morning begins quiet with patchy fog, especially in the river valleys though fog should mix away quickly with the sunrise. Temperatures will remain warm in the low to upper 70s quickly warming into the upper 80s and low 90s in the afternoon. During this time, a subtle shortwave will be moving across the upper Ohio Valley which will help focus convective activity in a broken cluster of scattered storms that will move in from west to east. Timing will be near 17-19Z in the west, though a spotty storm further east at this time can't be ruled out with typical summertime convection. PWATs will remain high ranging 1.9-2.1+", especially along the axis of the shortwave to move in from the west. In our western CWA, storms will arrive earlier in the day, moving through before the best instability from daytime heating is reached. However, areas generally east of I-65 will have more time to destabilize ahead of the broken clusters of storms. Despite the weak shear aloft, MLCAPE and very high PWATs may be enough to create wet downbursts bringing damaging gusty winds that have the potential to bring down trees and power lines in isolated places. SPC has placed a Marginal Risk for these concerns in these areas east of I-65 including Louisville. Flash flooding is another concern considering the elevated PWATs and any preceding storms occurring before the axis of the shortwave arrives dumping high amounts of rain in short periods. HREF 6hr LPMM guidance is suggesting isolated areas of 3-4+" is possible in areas that receive more than one downpour from storms, though generally, the whole CWA has a 50-75% chance to receive 0.25-0.75" of rain by the evening. Around 8-10 PM, storms end in the east with another quiet night heading into Saturday.

Patchy fog returns Saturday morning with dewpoints remaining high in the low 70s with lows not much warmer if at all. Skies remain generally clear with scattered cumulus returning again in the afternoon. PWATs along with the same stagnant, humid air mass will remain high near 2.0". Spotty storms are possible in the afternoon bringing another low end threat for flash flooding along with lightning and gusty winds, though most storm coverage won't occur until the cold front moves into the CWA late Saturday evening into overnight Sunday. Sweeping in from the north, a line of storms along this front will bring in a risk of damaging wind gusts, flash flooding, and lightning. The strongest shear seems to remain out of the CWA, but 0-6km shear from HREF guidance approaches ~20kts nearest Jefferson County, IN. As a result, a Slight Risk was issued along our northeast CWA border. Timing seems to be the greatest limiting factor as storms may not move into southern Indiana until after 8PM, with the best daytime heating having already waned by then. As the cold front continues to move southward, continued nocturnal cooling will lessen the severe risk, although gusty winds will still be possible. Highs on Saturday will be in the upper 80s and lower 90s before the storms arrive. Heat indices will make both Friday and Saturday uncomfortable reaching 100 both afternoons from the elevated humidity present. Once the cold front begins to clear the northern CWA, PWATs will drop behind the front leading to drier conditions at least in northern communities.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

Issued at 337 AM EDT Fri Jul 17 2026

===== Sunday - Thursday =====

Behind the front on Sunday, albeit a slight reprieve from higher heat indices in the northern CWA, skies will clear and heat indices will be near the high temperature of the upper 80s and low 90s. Being a trailing cold front, the front may not actually clear southern communities in the afternoon as PWATs will remain elevated near 1.8", meaning scattered storms may return in the afternoon from a west-to-east area south of E-town according to latest LREF guidance trends. Given the pattern, PoPs of 50-70% will continue in these areas with the same risks as afternoons before being lighting, gusty winds, and low-end flash flooding from weak flow aloft allowing storms to be nearly stationary until they rain themselves out.

For Monday afternoon, moisture being advected in from the southwest from a high pressure to our south and in advance of a potent low from southern Canada will increase heat indices to near 100 again along with highs near 90. A spotty storm is possible again although with the lack of synoptic lift, coverage will be limited.

Focus should be given to Tuesday afternoon as a potentially strong low from southern Canada draws closer bringing a cold front over the area. With surface to 500mb shear near 30kts or more, and increasing moisture at the surface, organized convection across our northern CWA is possible though uncertainty exists with the exact timing, location and strength of these storms. The orientation of the shear with the front will determine the severe weather type as well. For now, storm chances increase in the evening hours with highs near 90 again.

For Wednesday and Thursday, the pattern suggests NW flow behind the passing low bringing drier and cooler highs in the low to mid 80s. This trend may continue into the weekend though more time will be given as those days approach.

AVIATION /06Z TAFS THROUGH 12Z SATURDAY/

Issued at 130 AM EDT Fri Jul 17 2026

Mostly clear skies with calming winds will linger through the overnight. BWG may briefly fog over before 12Z before fog mixes away after sunrise. Then, winds will be light during the morning and afternoon hours generally out of the WSW with scattered clouds. Storms will return from the west that could drop visibilities and ceilings with VFR conditions between storms after 18Z across all terminals. Otherwise, VFR conditions are expected through the TAF period.

LMK WATCHES/WARNINGS/ADVISORIES

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