textproduct: Louisville

KEY MESSAGES

* Scattered thunderstorms will bring heavy rainfall, lightning, and gusty winds to south-central Kentucky this afternoon and evening.

* Strong to severe thunderstorms are likely on Tuesday. Damaging winds and tornadoes are the main threats. Heat indices will be in the 100-110 degree range outside of storms Tuesday afternoon.

* Calm weather moves in with cooler than average highs for Wednesday through Friday this week.

SHORT TERM /THROUGH MONDAY/

Issued at 352 PM EDT Sun Jul 19 2026

A strong mid/upper level ridge remains centered over the Rockies, with weak NW flow aloft over the Lower OH Valley. Sfc high pressure is shifting across the Great Lakes, and a weak cold front has pushed through southern IN and northern KY. A very warm, moist airmass remains in place south of the boundary. Scattered weak convection has begun to develop this afternoon, mainly across south-central KY where PW values slightly exceed 2 inches. MLCAPE is peaking around 2000-2500 J/kg south of I-64 this afternoon, but effective deep shear is very weak at 15-20 kts. The moisture-rich, moderately unstable environment will support pulse convection capable of locally torrential downpours and gusty winds. Though the risk for organized severe weather is very low, precipitation loading could enhanced downward momentum and produce an isolated wet microburst. Scattered convection will continue through sunset before gradually diminishing.

Temperatures have risen into the mid 80s to near 90 this afternoon. Conditions will dry out tonight, with temperatures settling into the mid 60s (north) to lower 70s (south) early Monday. On Monday, a potent low pressure system will develop east across Ontario and the Upper Midwest. We'll still have the weak, stalled frontal boundary in the vicinity of south-central KY. Isolated pulse convection appears possible Monday afternoon. Coverage should be much less than Saturday and even today.

LONG TERM /MONDAY NIGHT THROUGH SUNDAY/

Issued at 352 PM EDT Sun Jul 19 2026

===== Severe Storms Likely Tuesday =====

A rather interesting pattern for late July is set to bring a round (or two) of strong to severe storms on Tuesday. While confidence in detailed timing is low, forecast confidence in severe weather is high. A potent upper level trough and mid/upper level speed max will stream southeast over the Upper Midwest and Great Lakes on Tuesday. A sub-995 mb sfc low is forecast to spin across the ON/QC border Tuesday morning, with a trailing cold front pushing southeast through the Midwest. Recent model guidance has increased confidence that we'll likely have an MCS ongoing across portions of IL/IN at 12Z Tuesday, and this activity could push into portions of southern IN and central KY between 12-18Z Tuesday. One or more line segments appear possible, which could be capable of heavy rainfall and gusty winds.

Any areas that see morning convection will likely need a little extra time to destabilize, but this shouldn't take long Tuesday afternoon with a hot, humid airmass in place. Low-level SW flow will steadily advect warm, moist air into the region ahead of the seasonally strong cold front. The mid-level trough axis pivots southeast across the Great Lakes Tue evening and overnight, with 45 kt mid-level NW winds over the OH Valley. Low-level WSW flow produces some veering, with effective bulk shear more than sufficient for organized convection and rotating updrafts. It appears organized multicells or supercells could develop ahead of one more line segments Tue evening and overnight. Scattered to numerous thunderstorms are possible Tuesday afternoon into Tuesday night, and the main threat is damaging winds. Given the shear profile and potential for supercells, tornadoes and isolated large hail are also on the table. And depending on line orientation of any linear features, 0-3 km shear will likely be sufficient for embedded mesovortices.

Convective evolution on Tuesday remains fairly uncertain at this time range, and will depend on Monday night activity. Outside of thunderstorm activity, temperatures will have an opportunity to surge into the lower 90s Tuesday afternoon. Heat index values may exceed 100-105 for a short time, and a Heat Advisory may be needed once the convective and sky cover forecasts become more clear.

The sfc cold front will push through central KY Tuesday night, with the overall severe weather risk diminishing substantially by Wednesday morning.

Beyond Tuesday, surface high pressure builds in with a predominant NW flow at higher levels bringing in cooler and drier air for Wednesday through Friday. Highs will be in the low 80s with the coolest day being Thursday. Some places may not reach 80 degrees at all in the afternoon then. Eventually, by Friday afternoon and into Saturday, SW flow on the backside of the surface high returns with seemingly typical afternoon convection on Saturday afternoon, highs reaching the upper 80s and low 90s once again.

AVIATION /18Z TAFS THROUGH 00Z TUESDAY/

Issued at 202 PM EDT Sun Jul 19 2026

A weak cold front continues to sink south through central KY. A stripe of SCT-BKN lower clouds is still flirting with MVFR across central KY near the boundary, but these clouds will continue to slowly lift through 21Z. Scattered shra/tsra have begun will develop and will likely continue through sunset before gradually diminishing. Coverage of TSRA will be highest south of the boundary, which means BWG and RGA have relatively higher chances at seeing brief IFR conditions in a thunderstorm this afternoon. Mainly dry conditions are likely overnight with light winds. Some patchy fog will be possible early Mon morning, particularly at BWG.

LMK WATCHES/WARNINGS/ADVISORIES

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