textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Extreme Heat Warning in effect for all of southern WI noon today through Tuesday evening. Additional heat headlines will likely be needed for the middle to late portions of the week as this prolonged heatwave continues.

- Isolated showers and storms Then additional daily storm chances Tuesday night through the end of the week as the hot and humid pattern continues.

- High swim risk conditions for Ozaukee and Sheboygan County beaches today, with moderate swim risk conditions for Milwaukee and Racine Counties.

UPDATE

Issued 657 AM CDT Mon Jun 29 2026

Dewpoints of 72 to 76 degrees have advected in overnight, with strong warm and moist advection continuing through today. Expecting heat index values to easily reach Extreme Heat Warning criteria. With such high dewpoints, also not anticipating temperatures to fall below 75 degrees tonight. High swim risk conditions are expected for Ozaukee and Sheboygan County Lake Michigan beaches through 10 PM CDT, with moderate swim risk conditions for Milwaukee and Racine Counties. Stay out of the water if in a high swim risk area. Avoid dangerous areas such as piers and breakwalls!

MH

SHORT TERM

Issued 1044 PM CDT Sun Jun 28 2026

Tonight through Tuesday:

The nose of a sly low level jet around 35-40 kt will remain over nrn and central WI tnt. Thus new elevated showers and storms will develop over this region due to the low to mid level warm, moist advection and embedded frontogenesis. Believe the 12C isotherm at 700 mb will remain a good indicator of capping to the south, while enough lift and moisture for storms will prevail to the north. Thus east central WI will at least be on the srn periphery of this new area of convection. Forecasting 50 percent chances toward central WI late this evening and overnight with only slight chances from Madison to Milwaukee.

The surface warm front will then pass nwd through srn WI from 09-15Z Mon as low pressure tracks from the central high plains into the Dakotas. A hot, humid, and well capped airmass will then prevail for Mon-Tue. High temps in the lower to middle 90s with dewpoints in the middle 70s will yield heat index values of 100-110F. An Extreme Heat Warning is in effect.

Gehring

LONG TERM

Issued 1044 PM CDT Sun Jun 28 2026

Tuesday night through Sunday:

The heatwave will continue much of the week. The strong upper ridge axis will gradually shift to the east and south becoming a west to east upper ridge from the ern Ohio Valley to the ern Seaboard by Wed, and lasting through the week with only minor weakening. Meanwhile a series of shortwave troughs will continue to traverse from the wrn USA into the Upper MS River Valley and nrn Great Lakes. Thus the storm track will mainly remain to the west and north of srn WI through Thu with 500 mb heights at 588 DM or greater. This continues to place a hot and humid airmass over srn WI through the week. Extreme Heat Warnings or Heat Advisories will likely be needed much of the week. Only 20-40 percent chances for showers and storms toward central WI for Tue nt-Wed nt with chances increasing a bit for late in the week and weekend as shortwave troughs arrive in wly flow aloft.

Gehring

AVIATION

Issued 657 AM CDT Mon Jun 29 2026

A few patches of fuel alternative ceilings have developed across south-central to southwestern Wisconsin this morning. These are expected to lift and scatter out within the next couple hours. After clouds lift and scatter, expecting VFR conditions to prevail throughout the TAF period. Gusty south-southeasterly winds of 20-25 kt starting midday and continuing into this evening. Overnight, expect wind gusts to diminish but LLWS to develop. Winds will shift to southwesterly overnight, becoming gusty around 20 kt again Tuesday morning.

MH

MARINE

Issued 1044 PM CDT Sun Jun 28 2026

Low pressure around 29.2 inches in eastern Colorado will track to eastern North Dakota by Monday afternoon. Its warm front will move north across Lake Michigan on Monday. Light to modest easterly winds this evening will become breezy southeasterly winds late tonight and Monday morning over the lake. Breezy south winds will then prevail from Monday afternoon into the middle of the week. Modest southerly winds will then prevail for Thursday into Friday. Areas of dense fog may develop at times this week due to a very humid airmass flowing over the relatively cooler waters of the lake. Scattered thunderstorms are forecast on most days especially over the north half.

Gehring

MKX WATCHES/WARNINGS/ADVISORIES

WI...Beach Hazards Statement...WIZ052-WIZ060 until 10 PM Monday.

LM...Small Craft Advisory...LMZ643 until 10 PM Monday.

Small Craft Advisory...LMZ644-LMZ645-LMZ646...noon Monday to 10 PM Monday.