textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Additional rainfall moving west to east will bring up to an additional inch of rainfall, leading to local ponding of water and potential for river flooding.

- Seasonal temps and dry weather Sunday into early next week.

- Return to an active pattern Tuesday night through the weekend, with chances for rain and storms developing on and off through the week.

SHORT TERM

Issued 1230 AM CDT Sat Apr 4 2026

Today through Sunday night:

Severe thunderstorm threat has diminished greatly over the last few hours, with mid-level instability too strongly undercut by the cold airmass at the surfaces. MUCAPE gradient is leaning into Lake Michigan as the parent low propagates into southern Wisconsin this morning, so any lingering threat remains tied to long- duration rain and storms. Expecting up to an additional inch of rain in many areas, which is expected to lead to local ponding of water and rising rivers.

Temperatures in the mid-30s have been observed across all of southern Wisconsin for the last several hours, and although expectations remain for temperatures to remain above freezing, cannot rule out a localized lower elevation area seeing temperatures fall to freezing for a few hours early this morning and allowing for patchy freezing rain. This is especially true for Marquette, Green Lake, Fond du Lac, and Sheboygan Counties, but could dip down into the Dodge/Washington County areas as well. Not anticipating widespread impacts. Temperatures will rise into the upper 30s and low 40s just before sunrise as low pressure propagates through the region, bringing a wave of warmer surface air with it. This will bring an end to any freezing rain concerns.

Overcast skies continue throughout the day, with high temperatures in the upper 40s to low 50s and breezy westerly winds around 25 mph. During the afternoon hours, wrap-around showers and sprinkles may develop across southern Wisconsin (~15% chance, isolated to scattered coverage). A few flurries may develop overnight as temperatures fall to just below freezing. All precipitation ends by Sunday morning.

Highs around 50 degrees expected Sunday, before 500 mb shortwave works its way southeastward through Wisconsin Sunday evening through Sunday night, bringing isolated to scattered rain showers to the region (15-30% chances). A few snowflakes could mix in at times, with temperatures in the low to mid-30s Sunday night as Canadian high pressure builds into the region.

MH

LONG TERM

Issued 1230 AM CDT Sat Apr 4 2026

Monday through Saturday:

The aforementioned 500 mb shortwave looks to phase with the lingering remnants of a cold front draped across the Ohio Valley, allowing the shortwave to deepen a surface through and bring in additional precipitation on Monday. Current expectation is that the majority of this precipitation will be confined to northern and central Wisconsin as high pressure builds into the Upper Mississippi Valley and presses moisture northward, but cannot rule out a few showers (~15% chances) in southern Wisconsin on Monday.

High pressure then dominates Monday night through Tuesday, before quickly moving eastward in advance of a low pressure system propagating through southern Canada Tuesday night through Wednesday. Chances for precipitation return with this system as warm frontogenesis develops over Wisconsin Tuesday night, although confidence in coverage is not high at this time (keeping NBM PoPs around 20-40%). Temperatures in the warm sector on Wednesday will rise into the mid 60s away from Lake Michigan. Overnight Wednesday, a weakened cold front from this system looks to push southeastward through the Upper Midwest, but looks to stall as the low continues its eastward progression and weakens while low pressure develops in the Colorado Rockies on Thursday. Models diverge with solutions for this low, some tracking it rapidly through the Upper Midwest, while others have it deepening and tracking southward. An active pattern remains in play through Saturday.

MH

AVIATION

Issued 1230 AM CDT Sat Apr 4 2026

Isolated thunderstorms continue across southeastern Wisconsin, while a line of thunderstorms with trailing rain showers moves eastward through southwestern Wisconsin. Expect this line of storms to continue eastward, exiting into Lake Michigan by daybreak. Temperatures hover near 33 degrees F at SBM, but still expecting little to no freezing rain concerns. Temperatures will begin to rise before sunrise as low pressure moves overhead. Low pressure overhead will bring IFR ceilings and briefly lower winds, turning to become westerly and gusting at 20-25 kt after sunrise as low pressure exits to the east. Expect ceilings to recover into MVFR into midday/afternoon, but isolated to scattered rain showers with snowflakes mixing in at times (15-30% coverage) develop during the evening to overnight hours and may briefly reduce ceilings as they move overhead.

MH

MARINE

Issued 1230 AM CDT Sat Apr 4 2026

Northeasterly winds will continue to gust near 30 kt into the early morning hours, with a few gales expected in the far northern portions of the lake. Winds will gradually veer through the day Saturday as low pressure around 29.6 inches crosses the northern portions of the lake. Thunderstorms will continue across the southern half of the lake through the early morning hours, with lightning as the main threat. Thunderstorms will end into the mid-morning hours as low pressure exits into Ontario and deepens to 29.3 inches. Expect winds to become westerly and gust again around 30 kt through tonight as this low deepens.

Winds veer northwesterly and gradually diminish Sunday as low pressure exits into northern Quebec. A weak low around 30.0 inches in southern Quebec will bring gusty conditions again Sunday night into Monday morning, with winds remaining northwesterly. As low pressure exits into Monday night, expect a few gales to develop and winds to shift northerly. High pressure builds into the Upper Midwest into Tuesday, with winds becoming light and variable. Winds shift back to southerly as low pressure develops in the northern Plains into Wednesday.

MH

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 1 PM Sunday.