textproduct: Milwaukee/Sullivan

KEY MESSAGES

- A clipper system brings higher-end shower chances (50 to 80 percent) for Tuesday morning. A passing cold front Tuesday afternoon may bring a few thunderstorms. Gusty winds and small hail may occur with the strongest storms, if they develop.

- A cool and cloudy day is expected for Wednesday.

- Relatively warm and humid conditions with increasing storm chances returns from Thursday night into the weekend.

SHORT TERM

Issued 230 PM CDT Mon May 11 2026

Tonight through Tuesday night:

Models continue to support a fairly strong shortwave trough across nrn MN and the nrn Great Lakes tnt-Tue. The NAM and ECMWF continue to want to develop a wave of low pressure that tracks across central WI during this time. Despite the models trending a bit drier over far srn WI, still expect a well organized swly low level jet of 45-50 kt and warm, moist advection pattern to bring sufficient moisture and lift for widespread showers and perhaps scattered elevated convection. Small chances for sfc based convection along a weak wind shift or cold frontal passage remains for mid to late Tue afternoon. Only very marginal CAPE is expected given the high dewpoint bias of the NAM and GFS.

A shortwave trough in nwly flow aloft will then follow for Tue evening, while a stronger upper wave digs from the Lake Superior region across the nrn half of Lake MI. Although these features may not produce any precipitation, cold advection and some low level moisture may lead to widespread stratus clouds going into Wed. High pressure will then follow for Wed nt-Thu.

Gehring

LONG TERM

Issued 230 PM CDT Mon May 11 2026

Thursday night through Monday:

Synopsis: With high pressure departing to the east of the region, southerly wind components will return to the western Great Lakes through the end of the work week, allowing for temperatures to quickly rebound after the mid-week cool down. Bouts of cooler/non- southerly winds will be short-lived from the weekend through the beginning of next week, allowing for above-normal temperatures to stick around through the conclusion of the period. Active surface & upper level patterns will accompany the warmer temperatures, with upper disturbances & affiliated surface frontal passages supporting multiple chances for showers & embedded thunderstorms. Thursday night into Friday and Sunday into Monday are the currently favored windows for shower & storm activity. Details regarding more precise timing---in addition to any potential for hazards---will be fine- tuned over coming forecasts as timing & mesoscale uncertainties clarify.

Thursday night through Friday: First of two upper disturbances will approach the western Great Lakes from the Northern Plains, bringing returning shower and storm chances to southern Wisconsin. Current progs point toward areas of storm development over the Northern Plains Thursday afternoon/evening as the disturbance ejects from the Rockies, with the remnants of activity moving into the region later Thursday night/predawn Friday within a wing of increasing low level warm advection. Initial forecast soundings from global forecast guidance point toward generally decreasing instability moving deeper into the overnight, with currently-progged values being too meager to support severe weather potential. Will nonetheless be watching trends over coming updates. The responsible upper disturbance will migrate across the western Great Lakes during the daytime hours Friday, dragging an attendant surface cold front through southern Wisconsin at some point during the afternoon/evening hours. If enough recovery can occur between daybreak showers/storms & the frontal passage, additional showers & storms would be possible Friday afternoon & evening. It remains too early to speculate on any hazards potential in this possible development given the aforementioned uncertainties, with trends being monitored over coming forecasts.

Sunday through Monday: The second meaningful upper disturbance & surface front of the period will move through southern Wisconsin, bringing additional chances for showers and storms. A bimodal set of timing solutions is apparent in current medium-range ensemble guidance, with a seemingly equal number of members favoring Sunday versus Monday as the peak time period for storms. Which solution verifies will ultimately depend on how progressive the disturbance & front are, with better forecast agreement anticipated over coming forecasts.

Quigley

AVIATION

Issued 230 PM CDT Mon May 11 2026

VFR conditions this afternoon and tonight. High based showers and possibly isold storms will develop late tnt and increase in coverage through Tue morning. Cigs of 3.5-5.0 kft will develop on Tue but patchy MVFR Cigs toward east central WI will be possible. Breezy sly winds will develop Tue AM shifting wly by mid to late afternoon. Isolated to scattered storms will be possible Tue afternoon especially over se WI.

Gehring

MARINE

Issued 230 PM CDT Mon May 11 2026

High pressure around 30.3 inches over the northern and western Great Lakes this afternoon will move to the lower Great Lakes tonight, while low pressure around 29.7 inches moves into northern Minnesota from the Canadian Prairies. The low will then track to central Lake Michigan by early Tuesday evening and to the lower Great Lakes on Wednesday. Light and variable winds over Lake Michigan will become breezy southerly winds on Tuesday with a few gale force gusts possible. The winds will then shift west to northwest with a cold frontal passage Tuesday evening. Breezy northwest winds will then continue into Wednesday.

High pressure around 30.1 inches will then move over Lake Michigan for Thursday into Thursday evening. The high will move east on Friday with breezy south winds returning.

A Small Craft Advisory has been issued for Tuesday into Wednesday afternoon from Sheboygan to Winthrop Harbor for breezy sly winds shifting nwly. High waves are expected Tue into early Tue evening.

Gehring

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646...9 AM Tuesday to 4 PM Wednesday.