textproduct: Louisville

KEY MESSAGES

* Unsettled weather with localized areas of heavy rainfall and flash flooding are possible in KY and southern IN Monday - Tuesday midday. Localized amounts of 3-6" of rain will be possible in the heaviest swaths.

* Despite some morning showers and weak storms on Wednesday, hot temperatures and mugginess are expected Wednesday and Thursday, with peak afternoon heat index values between 90-100.

* An approaching cold front later in the week provide more opportunity for rain and some strong storms Thursday evening through Friday, though timing is still uncertain.

SHORT TERM /THROUGH TUESDAY/

Issued at 339 AM EDT Mon Jun 8 2026

The upper ridge axis stretching from the Gulf Coast up through the Great Lakes region will slide east today. Meanwhile, a slow moving shortwave trough will begin to slide into our region. As this occurs, ample deep moisture will move into our area ahead of the shortwave trough axis. The meandering upper disturbance then hangs around through Tuesday, before departing as we head into mid week.

PWATs will surge into the 2-2.25" range today which is above the daily max climatology. In addition to the high moisture content through the atmospheric column, we will likely develop some modest to moderate instability today with HREF probs for 1000 J/KG of ML CAPE in the 20-40% range, and in the 60-70% range for at least 500 J/KG. The end result will be a tall/skinny CAPE profile more indicative of a tropical airmass. The freezing level will also be above 14k feet, which will allow for more efficient rainfall processes thanks to collision and coalescence. Fully expect to see low centroid radar presentation on the stronger showers/storms. The final piece of the puzzle will be deep layer flow, which will be pretty weak with 0-6 km bulk shear magnitudes only in the 15-20 knot range. The slow storm movement combined with all of the factors creating efficient/intense rainfall rates will result in pockets of locally heavy rainfall through Tuesday.

There has been a consistent signal in the HREF PMM and LPMM data for these pockets of intense rainfall, including some localized 5+" amounts showing up. Given that pretty much all of the boxes for heavy rain are checked, do think that this is reasonable. WPC also agrees and has our area in a higher end Slight Risk for Excessive Rainfall today (25% probs of exceedance over western CWA), and again tomorrow. As a result, have lifted a Flood Watch (Flash Flooding due to intense rates) in coordination with several surrounding offices for our western two-thirds of the CWA where the heaviest rain is anticipated to fall. This will go through early Tuesday evening when things should start to improve with the departing upper shortwave. It is worth noting that we only expect isolated instances of flooding, however given the setup and some of the data suggesting localized big amounts, some of those isolated areas could see some notable impacts from flash flooding. 1,3, and 6 hour Flash Flood Guidance is running quite robust (3-5" for 6 hour FFG across the area), however short term hourly rates could exceed 2 or 3 inches per hour over shorter spurts, and 1 hour FFG values are more around 2".

The other thing we will have to keep an eye on is for a localized wet microburst wind threat with any stronger cell as a water-loaded downburst could occur in this environment. Especially, if we realize some of the stronger instability values offered by the Nam (not likely given its low level moisture and instability bias). SPC did add a Marginal Risk for wind across our western tier of counties, but will have to monitor other storms as well. Given what has occurred upstream closer to the center of the upper low the past 2 days, we will also have to be vigilant of a few rotating storms across our west later this evening. Overall, the deep layer shear profile does not look that favorable for any rotating storms/tornado potential, but also don't want to ignore what occurred upstream. Therefore, can't completely take it off the table.

Overall, will be messaging a more widespread 1 to 2" of basin average QPF now through late Tuesday, but again those localized rainfall amounts over 3"+ are also expected. Some more extreme amounts of 5"+ also seem feasible given the setup. Best chance for the higher amounts are expected west of I-65. Flood Watch begins at 2 PM EDT today, and will run through 8 PM EDT on Tuesday. Another noteworthy portion of this forecast will be the humidity as dew points in the lower 70s combine with temps in the 80s.

LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/

Issued at 339 AM EDT Mon Jun 8 2026

Wednesday - Wednesday Night...

Beginning Wednesday morning, temperatures will be warm for this time of year in the low to mid 70s. Continued SW flow will dominate as the shortwave causing all the rain earlier this week will slowly exit towards the northeast. However, as the previous discussion had mentioned, there is a continued signal of an MCS in deterministic long range model guidance descending from central IL/IN. With continually weak shear Wednesday morning, low instability and high PWATs, the main threat would be a line of heavy downpours Wednesday morning more in our NE counties and lightning with any embedded storms. Long range ensemble mean rainfall totals for Wednesday morning paint an additional T to near 0.5" of rain for areas north and east of Louisville. Otherwise, rain clears as an advancing ridge from our southwest moves over the Ohio Valley.

During the day on Wednesday, a deepening ridge from the surface through 500 mb moves overhead. This will clear skies and increase high temperatures into the upper 80s to low 90s. Dew points throughout the day with continued SW flow remain in the low to mid 70s. With this in mind, muggy summer weather is expected Wednesday afternoon and for as long as this tropical air mass lingers over KY. Feels like temperatures will max out in the upper 90s to low 100s at times. Should consider checking on those without A/C and take breaks should you work outdoors for extended periods of time Wednesday. Confidence is high in oppressive heat from the high dew points and the potential to mix air temperatures at 850 mb to the surface that's expected to be 96-99th percentiles. After sunset, the ridge axis slowly shifts to the east, albeit with continued warm SW flow from the Gulf keeping dew points and temperatures high overnight. Need to monitor record warm lows for Thursday morning with this synoptic pattern. EFI tables indicate anomalously warm lows are possible in the low to mid 70s.

Thursday - Sunday...

Thursday morning is warm and will continue to be warm throughout the afternoon. Synoptic setup begins to shift Thursday as SW flow gets amplified from an impending trough swinging through the plains. With a strong high to our SE and the incoming trough, a tightening pressure gradient at low to mid levels is expected, mixing down breezy winds towards the surface with afternoon heating. Latest ensemble guidance suggests gusts of 25-30 MPH is possible on average, though this will be monitored as Thursday draws closer. With the amplified SW flow, dew points remain high and PWATs may raise closer to 1.8-1.9" again, meaning pop up storms in the afternoon are possible, though confidence in rainfall amounts is low. For now, an isolated shower or storm can't be ruled out with prime time afternoon heating. Highs on Thursday will be hot once again in the upper 80s to low 90s, with feels like temperatures maxing out in the mid 90s to low 100s once again.

Beyond the afternoon hours, the trough swinging through the central plains will create a trailing cold front that will move towards KY, albeit slowing and weakening as it does so. Timing of this front's arrival is uncertain, but may hold off until overnight Thursday into Friday morning. Should this occur, then any severe risk would be muted but will deserve to be watched as the event draws closer. Regardless, increased rain chances for later this week are expected until the timing of this front can be determined.

From Friday through the rest of the weekend, an unsettled pattern with passing shortwaves drawing close enough to bring more rain chances through Sunday is the current trend. Some guidance tries to bring in a more pronounced trough through and dry the area out, though that does not happen often this time of year. For now, continued highs in the 80s and low 90s will continue through Sunday.

AVIATION /12Z TAFS THROUGH 18Z TUESDAY/

Issued at 639 AM EDT Mon Jun 8 2026

VFR conditions to start this forecast period, but expect conditions to deteriorate to low-end MVFR and IFR later this morning into the afternoon. Rich moisture will surge in from the south just ahead of a mid-level shortwave trough lifting northeast over the Midwest. Numerous SHRA and scattered TSRA will develop across the region this morning and afternoon, with occasional rounds into tonight as well. Any shower or storm could have locally intense rain, so could see some brief vis reduction into the IFR range. Some improvement back to VFR is expected later this afternoon into the evening, but overall confidence in ceilings is low once the upper low approaches the area. Light SSE - S winds between 5 and 10 knots are expected through the period.

LMK WATCHES/WARNINGS/ADVISORIES

KY...Flood Watch from 2 PM EDT /1 PM CDT/ this afternoon through Tuesday evening for KYZ023>031-034-038-045-046-053-054- 061>065-070>078-081-082. IN...Flood Watch from 2 PM EDT /1 PM CDT/ this afternoon through Tuesday evening for INZ076>078-083-084-089>092.