textproduct: Louisville

KEY MESSAGES

* Widespread rainfall tonight into Wednesday will benefit the ongoing drought. Amounts of 1 to 2 inches will be most common, though a few locations (10% chance) may see totals surpass 3 inches. The risk of flooding is low but nonzero.

* The risk for severe weather is also low, though sporadic and localized gusty winds exceeding 40 mph may (20-30% chance) accompany heavier showers today.

UPDATE

Issued at 954 AM EST Wed Nov 4 2026

The cold front is poised to begin pushing through our area late morning through early evening. Ahead of this feature, periodic showers and a few storms are being driven by an intense low level jet beneath fairly strong mid to upper level jet structures. This setup is providing plenty of shear, especially in the lowest 3km, however the lack of overall instability will be a big limiting factor to most severe concerns. We will have to watch a very modest instability axis travel across our southern tier of counties through late morning into the afternoon ahead of the approaching cold front. Here, 100-250 J/KG of ML CAPE may be just enough to allow for some stronger storms where some of the higher momentum air above the ground may be realized at the surface in isolated pockets. Additionally, there is a very low (non-zero) chance of a brief spin up tornado down along the KY/TN border. This is a very low chance, but something we'll have to monitor in places where the 0-3 km shear vector becomes a bit more perpendicular to the mean winds in that layer. SPC did add a good bit of our southern tier to the Marginal Risk, with 2% tornado contour along the KY/TN border, and the 5% wind contour extending a tier of counties farther north.

Otherwise, rainfall totals will be the other focus. The KY Mesonet shows Allen county as the big winner for the moment with 1.9" of rain, however MRMS radar estimates have been pretty accurate and suggest the SW part of the county has seen over 2". May still have a round or two of moderate to briefly heavy rain to go for these areas so amounts over 2.5" are still possible. Elsewhere, most locations have seen between .5" and 1.5" with our far eastern tiers of counties expected to catch up a bit as we go through the day.

DISCUSSION

Issued at 253 AM EST Wed Nov 4 2026

At 245am EST Wednesday morning, a large upper level trough was spinning over the Midwest, with its associated 1000mb surface low positioned along the IA/MN border. Ahead of this low, deep southerly flow is pulling rich Gulf moisture northward across the Ohio Valley and Great Lakes Regions, with PW values of 1.5-1.8 inches along and west of the I-65 corridor in Kentucky and southern Indiana. As this low lifts north into the Upper Midwest today, its attendant cold front will gradually traverse the local area. Ahead of this front, gusty winds and heavy rainfall are concerns; behind it, winds will ease and rain come to an end, though clouds will linger the remainder of the day.

*** GUSTY WIND POTENTIAL ***

Scattered showers were percolating across the area as a low level jet (LLJ) promotes isentropic upglide. A somewhat stable planetary boundary layer (PBL) should in general limit the transfer of momentum from the 50-55 kt winds clocked on KLVX's vad at 1km (~3200 ft) AGL, though sporadic gusts to 30+ mph (recently observed at SDF) may continue through dawn. Thereafter, various REFS members suggest a heavier band of showers will develop along the eastward-meandering cold front. REFS ensemble mean brings gusts to 30-40 mph with this wave of rain, and even gives 15-30% (highest south) chances for gusts over 40 mph between roughly the I-65 and I-75 corridors in Kentucky during the 8am to noon EST timeframe. It would make meteorological sense that this would be our best opportunity for those stronger wind gusts, as (1) winds aloft will remain strong during this time and (2) these heavier showers will feature the strongest downdrafts. Still, given widespread clouds and rain showers, low levels are forecast to remain somewhat stable, limiting mixing on the whole and keeping the coverage and duration of those stronger gusts low.

*** HEAVY RAIN POTENTIAL ***

In addition to gusty winds, widespread rainfall ahead of the front today should benefit the ongoing drought. The near-record PW values approaching 1.8 inches coupled with a 10-12 kft deep warm cloud layer suggests showers ahead of the front will be efficient rain producers with hourly rates approaching an inch at times. In addition, the orientation of mean cloud layer winds nearly parallel to the (slow-moving) cold front suggests training of heavier showers, which could allow some locations to see 3+ inches of rainfall in just a 6 hour period. REFS LPMM suggests this is most likely along and west of roughly the I-65 corridor, especially south of E-town where NBM maintains 10-30% probabilities (for 3+ inches). This would imply a nonzero (but still low) risk for flooding in urban and poor drainage areas, especially if any leaves clog storm drains. However, most locations are expected to see between 1 and 2 inches of rainfall, which is much needed.

The cold front will bring an end to the rain and gusty winds from west to east today, reaching I-65 around 1-2pm and the I-75 corridor around 5-6pm EST. Behind it, however, we'll hang onto clouds and may even see some patchy drizzle this evening into tonight.

*** EXTENDED PERIOD ***

Conditions will turn drier on Thursday and we may even see some breaks of sunshine during the afternoon ahead of the next shortwave trough which will pass through the Lower Great Lakes on Friday. The LREF suggests a 40-70% probability 850mb temps drop to sub 0 degC near and north of an Owensboro to Richmond line Friday into Saturday, which indicates our area will be cool to kick off the weekend. In fact, forecast highs are in the mid 50s for Saturday - much more seasonable for early November. Clouds Friday night should keep lows from falling too far, but Saturday night we may see some frost or even localized freezing conditions (particularly over the Bluegrass) as clear skies and light winds make for efficient radiational cooling. Continued northwest flow will maintain dry and seasonably cool conditions into early Monday, with a gradual warming trend next work week.

AVIATION /12Z TAFS THROUGH 18Z THURSDAY/

Issued at 626 AM EST Wed Nov 4 2026

Scattered showers will continue over the area the next several hours, bringing occasional ceiling and especially visibility drops into the low MVFR or IFR category. Meanwhile, a wave of heavier rain, locally gusty winds to 30 kt, and perhaps (10-20% chance) a lightning strike or two will work through the area from west to east during the 14-19z timeframe. Even outside of these gustier showers during the late morning-early afternoon, winds will be gusting over 20 kt at times from the south. Once the showers clear the area during the afternoon, winds will switch around to the southwest and drop off dramatically. We may have some patchy drizzle behind this front as MVFR ceilings linger into the evening, especially at LEX/RGA.

LMK WATCHES/WARNINGS/ADVISORIES

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