textproduct: Louisville

KEY MESSAGES

* Near record heat... Highs in the upper 80s to low 90s are possible Tuesday. Wednesday is warmest in the south ahead of incoming rain. * Rain chances increase sharply Wednesday for another widespread rainfall event mixed with storms and a low-end severe threat for gusty winds.

* Rain chances linger Thursday before a cold front pushes through increasing the potential for our first frost Saturday night.

DISCUSSION

Issued at 348 AM EDT Tue Oct 13 2026

===== Summery Warmth and Waves of Rain Midweek =====

After a quiet weather day, the overnight hours have been just as calm. Light ongoing southerly winds are keeping the air from settling and decoupling completely. However, patchy dense fog in valleys particularly in the Cumberland River Valley is trying to form. Should you find yourself driving near the area of Allen to Russell Counties, expect brief bouts of reduced visibilities.

Any fog though will dissipate more quickly than yesterday's fog as a stronger SW flow moves through our area, with wind gusts as high as 25 mph today (in isolated areas). Sunny skies with this southwest flow will boost temperatures well into the 80s and low 90s. With this warm air flowing in, some warm record minimums and max temperatures may get a little nervous today. Otherwise, today is rather pleasant despite the unseasonable heat and will end with temperatures cooling to near warm record minimums again.

Beginning Wednesday, the high pressure responsible for the SW flow will begin to drift south just a little bit allowing an extended SW- NE oriented jet streak along a trough to nudge into our Indiana counties first and become more west-to-east oriented by the afternoon. This boundary seems to be very well saturated, especially as the day progresses. Incoming moisture from the Gulf will boost PWATs near or over 2.00". The whole CWA has a near 100% of PWATs over this threshold which is ridiculously high. The only the problem as that in order to get heavier downpours, pre-existing areas of convection will have to be the culprit as there may not be much in the form of lift besides diurnal heating. However, modeled profiles suggest strong moisture transport at 850mb, and parallel flow up to 700mb along this incoming boundary. This indicates the potential for heavy downpours with any rain mixed with thunderstorms may produce as they move generally east into our CWA. Rain showers mixed with potential storms will first approach our southern Indiana counties by late morning Wednesday and drift SE from there towards TN by the nighttime hours. General rainfall totals still look to be somewhat healthy, with 25th-75th percentile ranging from as little as a tenth to as high as 2". HREF 6hr LPMM data suggests localized 2-4" are possible considering the moisture that will be in place. Overall, TN border counties may have to wait until overnight Wednesday into Thursday for any rainfall, and the heaviest rain totals will be where communities are closest to the slowly approaching boundary in southern IN generally around 0.5-1" and under 0.5" south of the Ohio with the potential for this total to increase rather than decrease as more CAMs can simulate these waves of rain. One last thing to note would be the potential for strong gusty winds with any of these storms. Peak heating hours suggest the greatest Marginal severe risk from just winds would be located in the Bluegrass region and will need to be watched for any further development or expansion of this risk. Any severe risk though will be quite limited given the lack of best shear and instability during the week throughout the profile. Lastly, highs on Wednesday will vary greatly with a rather sharp gradient of temperatures from NW to SE due to rainfall timing. Highs should range anywhere from near 80 or just below in southern Indiana to the upper 80s near the TN border.

By Thursday, the nearby boundary may stall over the Ohio with another gradient of temperatures possible (cool to the north and warm to the south). However, the aforementioned jet streak should allow and give energy to a developing low over the Great Lakes, allowing the best moisture along the boundary to lift north and a return to SW flow again. Near record highs are possible again nearest the TN border and this all depends on how quickly the boundary can lift back north again. Spotty showers or a few storms are possible again although the greatest chances of rain remain to be on Wednesday. Highs range from the low to upper 80s once again.

===== Incoming Cool Snap and Potential for Weekend Frost =====

Eventually, the developing low over the Great Lakes will finish the job and push the aforementioned boundary SE, clearing our whole CWA. A line of showers may be associated with this front, but more importantly, wind gusts will be high and gust anywhere from 20-30 MPH at times. Temperatures will plummet with 60s for highs in IN and warmer highs SE where the boundary will take the longest to clear. Regardless, a taste of fall looks to finally arrive with low temperatures falling into the low 40s and upper 30s.

Saturday may be the coolest day of all, as highs will really struggle to make it above 60 degrees. In fact, there is a growing potential for frost Saturday night into Sunday with lows as cold as the low 30s in the Bluegrass region. Sunday is cool as well although it appears a return to southerly flow is coming for early next week.

AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 709 AM EDT Tue Oct 13 2026

VFR conditions will continue this morning through overnight into Wednesday. South to SW flow will strengthen later this morning gusting 20-25kts at times. Sunny skies will prevail though and SW winds will weaken this evening. Heading into Wednesday morning beyond 12Z, BKN clouds will move in and showers from the west near 15Z at the end of the TAF period. Until that time on Wednesday, VFR conditions will continue.

LMK WATCHES/WARNINGS/ADVISORIES

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