textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Warm and humid conditions are forecast Sunday and last through much of the new week. Intermittent showers and thunderstorms are expected during this period. Severe storms and heavy rain will be possible at times. Rivers are expected to rise with some flooding possible.

- Gale Watch for the north half of Lake Michigan late Sunday afternoon into early Monday morning. Areas of dense fog will be possible at times over the lake from Monday morning through the end of the week due to a relatively mild and moist airmass over the cold waters of Lake MI.

UPDATE

Issued 700 AM CDT Sun Apr 12 2026

Scattering of showers and intermittent thunder continue across southern Wisconsin early this morning. Ongoing activity is being driven by broad warm/moist advection in the 925-700 mb layer, with embedded bands of frontogenesis helping to explain the broken northeast-southwest segments of precipitation on radar. Have adjusted near-term precip probs and weather grids to account for trends. Expect a gradual downtrend in activity moving into mid-day.

Apparent in current water vapor imagery over the southern Great Plains, a shortwave trough will progress into the western Great Lakes later this afternoon & evening, encouraging additional shower and isolated thundershower potential. Extrapolation of the feature points toward areas along/south of US-151 being most favored for precipitation, which is consistent with modeling. Expect mainly rain in this activity, though some very weak MUCAPE could support a few embedded thundershowers. No severe weather is anticipated in any thundershowers.

Quigley

SHORT TERM

Issued 1154 PM CDT Sat Apr 11 2026

Tonight through Monday night:

Low pressure around 994 mb over ern MT will track into ND tnt, while a swly low level jet of 45-60 kt continues to shift ewd across WI. The low to mid level warm, moist advection and frontogenesis is supporting the showers and isold storms over srn WI at this time with limited coverage toward the IL border.

The low pressure area will then track to the arrowhead of MN on Sunday with its warm front quickly shifting nwd across srn WI from 12-15Z Sunday. Some scattered showers and storms will likely continue in the morning as the frontal passage occurs, with perhaps greater coverage toward central WI as a weak shortwave trough tracks through the region. Despite what may be widespread cloud cover, temps should still reach around 70F within the warm sector with dewpoints possibly reaching 60F. Wind gusts of 30-35 mph are forecast.

A shortwave trough and its own sly 50 kt low level jet will then approach from the srn Great Plains for the mid to late afternoon and through the evening. Tall, skinny, surface based CAPE around 500 J/KG will be present with rain chances around 60-90 percent east and south of MSN, lesser chances to the north and west. The severe storm probability will remain very low, but cannot completely rule out damaging winds via momentum transfer if a stronger storm could develop.

The trailing cold front from the low over Ontario will then stall over central WI on Monday with subtle shortwave ridging aloft. Sly winds will continue to maintain a warm and humid airmass with perhaps some breaks in the cloud cover in the afternoon. Middle to upper 70s is forecast at this time. A weak shortwave trough will then track from the central Great Plains across central WI Mon nt. This will initiate a wave of low pressure and the nose of a strong low level jet over said region. The warm sector will be strongly capped but right along and north of the front, convective initiation and severe convection is likely. There are differences among the models on the aforementioned features and its certainly possible srn WI could see numerous storms, some severe, if a more southerly solution occurs.

Gehring

LONG TERM

Issued 1154 PM CDT Sat Apr 11 2026

Tuesday through Saturday:

A stationary front will reside in the vicinity of srn WI for Tue-Wed with possible weak vorticity maximums aloft that could set off new rounds of convection. A more organized shortwave trough will then approach from the sw Wed nt and pass on Thu providing more certainty for convection. Yet another stronger upper trough and sfc trough will move out of the Great Plains and into the wrn Great Lakes for Fri nt-Sat. In summary, multiple rounds of showers and storms are forecast from Tue-Sat, with a few inches or more of rain possible. River rises are expected with some flooding possible. Some severe storms will likely occur at times.

Gehring

AVIATION

Issued 700 AM CDT Sun Apr 12 2026

Rain showers continue over southern Wisconsin through late morning, with a lull anticipated through mid-day. Have accounted for near-term activity with TEMPO groups given its hit/miss nature. Have withheld any mentions of thunder & CB given an absence of lightning in satellite, but will continue to monitor trends. Currently over the southern Great Plains, an upper disturbance will bring additional precipitation to the region later this afternoon into this evening. Weak instability has motivated prevailing -RA mentions in the 12Z forecast, but did include PROB30 thunder mentions in the event CB approach any fields. Rain will conclude during the predawn hours. MVFR/IFR CIGs will set in with this afternoon's precip, and are expected to last through the remainder of the period. Will be monitoring for additional LLWS potential tonight as the low level jet increases once more.

Quigley

MARINE

Issued 1154 PM CDT Sat Apr 11 2026

Low pressure around 29.4 inches will track across the northern Great Plains to northeast Minnesota from tonight into Sunday evening, then develop toward Hudson Bay late Sunday night. This will bring breezy south winds to all of Lake Michigan, but with the potential for gales over the north half late Sunday afternoon into early Monday morning. A Gale Watch is now in effect.

Winds will weaken later Monday morning as the low quickly moves away and the trailing cold front stalls over northern Lake Michigan. Then, passing low pressure systems along the stalled front will lead to intermittent showers and thunderstorms through the middle of the week. Areas of dense fog will likely occur at times due to a relatively mild and humid airmass over the cold waters.

Gehring

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 4 AM Monday.

Gale Watch...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565...5 PM Sunday to 3 AM Monday.