textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Another round of showers and storms late this evening into the overnight hours. Just a very small potential for strong or severe storms.

- 30 percent chances for showers and isolated thunderstorms with the cold frontal passage on Tuesday. Severe thunderstorms are not expected.

- Cool and drier weather then returns for midweek.

- Rain chances return Friday into Friday night(40-60%), followed by a gradual warming trend Saturday into early next week.

SHORT TERM

Issued 1134 PM CDT Mon May 18 2026

Tonight through Thursday night:

The decaying MCS is now moving into sw WI and will continue to encounter much greater MLCIN and high LFCs. However, still expect fairly widespread showers and sct storms to move across all of srn WI during the early morning hours as a sswly low level jet of 40 kts increases warm, moist advection and boosts elevated CAPE to 1000-2000 J/KG. Wind gusts and small hail will be the main concerns.

A wave of low pressure along the stationary front from central IA to ern MN will track newd to near Lake Superior by 12Z Tue. The low will then track ewd into Quebec during the day with its trailing cold front moving across srn WI Tue AM into the early afternoon. Moist low levels and marginal instability could result in a broken line of showers and isold storms along the front but no severe wx is anticipated.

Nwly winds and cold advection will continue into Tue nt with low temps falling into the lower to middle 40s. High pressure will then move from MN to the nrn Great Lakes on Wed and remain there into Thu. Nely sfc winds and a relatively cool air mass will reside over srn WI with high temps in the 50s over ern WI and lower 60s over south central WI. A return of warm advection will bring 20 percent chances for showers west of Madison Thu nt.

Gehring

LONG TERM

Issued 1134 PM CDT Mon May 18 2026

Friday through Monday:

Low pressure ejects from the Southern Plains on Friday, with continued model discrepancies as to its progression. Canadian and Euro indicate a more southerly track of a single low pressure system bringing widespread rain and storms to southern Wisconsin throughout the day along the northern side of the low, while the GFS prefers a split pattern with one portion of the energy progressing through the lower Mississippi Valley and the other following the jet stream into Minnesota and brings a warm front with rain and storms into southern Wisconsin. Regardless of solution, probabilities of seeing rainfall have increased, so kept likely PoPs (50-65%) in the forecast for Friday afternoon into Friday night. Models also are inclined to agree that precipitation will taper off into Saturday as the warm front lifts north or the low pressure system exits to the east. Generally unsettled weather looks to develop Sunday through Tuesday as broad 500 mb troughing develops across the Upper Midwest, bringing multiple shortwaves through the region. As the upper level troughing develops, high pressure building in the Plains will bring increasing temperatures through the weekend into early next week. Monday and Tuesday temperatures could return to the mid-80s. However, weak, generally southeasterly winds will allow for Lake Michigan influence on temperatures in the easternmost counties.

MH

AVIATION

Issued 1134 PM CDT Mon May 18 2026

Numerous showers and scattered storms spreading west to east across srn WI during the early morning hours. Areas of MVFR Cigs and Vsbys may linger after the rain. More widespread MVFR Cigs will then overspread srn WI just after sunrise and ahead of the approaching cold front. Localized Cigs below 1 kft are possible over south central WI. The Cigs will dissipate after the cold frontal passage from mid to late afternoon. Gusty swly winds to 30 kts are expected on Tue especially over ern WI. VFR conditions for Tue nt.

Gehring

MARINE

Issued 1134 PM CDT Mon May 18 2026

A Dense Fog Advisory is in effect tonight through Tuesday morning for the north half of the lake as relatively mild and humid air flows over the cold lake waters. Otherwise modest to breezy southerly winds will develop tonight and last into early Tuesday afternoon, then followed by the passage of a cold front. Winds will shift to northwesterly with the cold frontal passage and remain a bit breezy. Scattered thunderstorms can be expected over the central and southern portion of the lake late tonight into Tuesday. High pressure around 30.4 inches will then move into the northern Great Lakes for Wednesday afternoon into Thursday. Light to modest north to northeast winds can be expected.

A Small Craft Advisory is in effect from Sheboygan to Winthrop Harbor from early morning Tuesday into the afternoon for breezy southwest winds.

Gehring

MKX WATCHES/WARNINGS/ADVISORIES

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

Dense Fog Advisory...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565- LMZ567-LMZ868 until noon Tuesday.