textproduct: Louisville

KEY MESSAGES

* Quiet weather is expected through tonight across the region, though a few light showers are possible in our northwest counties Thursday morning.

* Shower and storm chances will return by late Thursday and continue through Sunday morning. Excessive rainfall is likely across southern Indiana and portions of northern Kentucky. If current forecasts hold, flood watches will be needed in subsequent forecasts.

* Early next week the upper level pattern will shift allowing summertime heat and humidity to build across the region. Temperatures will warm to above normal with oppressive humidity and heat indices into the 100s early to mid week.

SHORT TERM /THROUGH FRIDAY/

Issued at 408 PM EDT Wed Jun 24 2026

With surface high pressure still in place, it has been quite a comfortable day across central Kentucky and southern Indiana, with temperatures in the upper 70s/low 80s and mostly clear skies. Conditions will continue to be pleasant through most of the night tonight, with lows in the low 60s forecast.

Looking more broadly, the area of surface high pressure over us will shift to the east, allowing southerly flow to return to the region. At the upper levels, fairly zonal flow will set in over the central and eastern CONUS, expected to last beyond the short-term forecast period. The cold front of a surface low over the Great Lakes region will drift southward towards central Indiana by Thursday afternoon stalling out near the Ohio River by late Friday. With all of these factors in place, in addition to several shortwaves expected to move over the region, this will help set the stage for a prolonged period of unsettled weather across the area.

For late Wednesday night into midday Thursday, a weakening cluster of showers and storms could skirt the northwestern portions of the CWA. With fairly dry air in place, as well as limited forcing/wind shear, the chances for appreciable precipitation are low (<15%). Conditions for most of the area will be dry during the day on Thursday, especially for places south of I-64. A band of showers and thunderstorms will develop ahead of the previously mentioned cold front over central Indiana Thursday afternoon, moving towards southern Indiana and north central Kentucky by late Thursday afternoon/Thursday evening. HREF PWs just ahead of the storms will be above 1.5", along with mean SBCAPE values at or above 1500 J/kg. Wind shear at the lower levels will be fairly low, so while there is not an increased concern for severe weather, gusty winds and small hail cannot be ruled out with the strongest storms. With the higher moisture in place, there is the potential for heavier downpours that could result in very localized flooding. Temperatures on Thursday will be closer to average, with highs in the mid-to-upper 80s.

Our first main wave of widespread showers and storms arrives late Thursday night as a mid-level shortwave enters from the west. With increasing near-surface southerly flow Thursday night, PW values will further increase to at least 2.0". The nose of an enhancing LLJ enters the region late Thursday night into Friday, and with the flow of the jet being near-parallel to the cold front, this should set up a favorable environment for training shower and thunderstorm development. Multiple shortwaves will move over the area late Thursday through Friday, as well as into the long-term forecast period. With the rich moisture in place, as well as decent instability profiles, any showers and thunderstorms that develop will be capable of producing heavy rainfall. NBM guidance at the 50th percentile outputs over 1" of precipitation north of I-64, with totals greater than 2" north of the Ohio River. 90th percentile outputs increases these values by at least 1", with the areas that could experience greater than 1" of rainfall dropping as far south as the Parkways. A Flood Watch will likely be needed for this period of showers and storms, as well as for the future waves during the weekend. With better overall wind shear in place Friday afternoon (0- 6 km shear >30 kt), as well as modest instability (>1000 J/kg), there is the potential for stronger storms to develop late Friday afternoon. The one limiting factor for severe development would be a cap at the 850 mb level that would introduce CIN across most of the CWA. While the potential for strong-to-severe storms does exist Thursday and Friday afternoon, the main concern we have during this timeframe will be the threat of more widespread flooding. Highs on Friday south of the rainfall will be in the mid-to-upper 80s, with places getting more persistent rainfall experiencing temperatures in the low-to-mid-80s.

LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/

Issued at 408 PM EDT Wed Jun 24 2026

Friday Night - Sunday Morning...

A quasi-stationary surface boundary is expected to be oriented W-E from the eastern Plains through the mid Atlantic. More regionally, it will be positioned just to our north across central IL/IN/OH. Given an orientation that will be parallel to the zonal flow aloft, expect several shortwaves embedded with the progressive flow to interact with the frontal boundary through much of the weekend. This is expected to lead to multiple rounds of showers and thunderstorms during that time. A modest low level jet (25-30 knots) is expected to respond at times beneath decent mid and upper flow around 30-40 knots. Overall, this is expected to provide enough deep layer shear for some loosely organized updrafts on Friday night. The shear profile should become more unidirectional and weaker with time into Saturday, but a few supercells and/or multicell clusters would likely be the dominant storm mode on Friday night. By Saturday, we would transition more to multicell clusters or even pulse modes. Expect that some severe threat will exist into Friday night before diminishing. Effective SRH values aren't expected to be nearly as high as the last couple events, but some some values around 150 m2/s2 could be just enough for a marginal tornado threat in addition to a wind threat.

The bigger concern, and the one we will be messaging the hardest, will be for potential training thunderstorms capable of efficient and very heavy rainfall. PWATs look to surge up into the 2-2.25" range along and south of the boundary, and this combined with forecast soundings showing a freezing level up near 15 K feet, tall CAPE profiles with overall instability values in the moderate range, and the potential to backbuild or train along the stalled frontal boundary thanks to the LLJ enhancement we could be setting the stage for a very heavy rainfall setup in spots. We aren't in the range of the PMM/LPMM data yet, but do expect that some locally very high rainfall totals will be possible, especially across the northern third of the CWA, outside of basin average amounts in the 3-4" range already offered by WPC. Given our recent heavy rainfall, and the potential for pockets/periods of torrential rain do think some Considerable Flash Flooding concerns could arise if current trends hold. Will likely need a Flood Watch at some point into the weekend.

Sunday Afternoon - Wednesday...

Strong upper ridging starts to take hold of the area later Sunday through mid week as a 595+ dam heights build at 500 mb. This is expected to quickly transition us to a drier (less rain), hotter, and much more humid airmass for early to mid next week. NBM/WPC are on the higher end of the guidance envelope, and like the previous idea of staying a bit more conservative with temps given recent heavy rainfall and greened up land cover. ECM 50th percentile temp data seems much more reasonable and more in tune with the overall temp guidance envelope. Still, with temperatures likely creeping into the low 90s and very high dew points in the 70s, we are looking at max heat indices each afternoon into the 100s. We'll likely be in Heat Advisory criteria at times, and given mild/muggy nights some of expected heat headlines could be prolonged. Overall, dry conditions should prevail under the subsident upper ridge, but could be close enough to the more volatile periphery of the upper ridge that perhaps some isolated shower or storm chances could develop each afternoon or evening.

AVIATION /18Z TAFS THROUGH 00Z FRIDAY/

Issued at 200 PM EDT Wed Jun 24 2026

VFR conditions are expected to prevail throughout the forecast period at all terminals. Surface high pressure will shift east of the region this evening, causing generally light and fickle winds to return from the south. Winds will slowly build out of the southwest late Thursday afternoon, and cloud ceilings will begin to lower, but remain VFR, over SDF and HNB near the end of the TAF period as a line of showers and thunderstorms develops off to the northwest.

LMK WATCHES/WARNINGS/ADVISORIES

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