textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Decaying squall line with gusty winds to move into south central and se WI during the early morning hours. Marginal probabilities for severe wind gusts over said region.

- Another round of showers and storms late tonight into Tuesday with a potential for strong to severe storms.

- Cool and drier weather then returns for midweek.

SHORT TERM

Issued 1200 AM CDT Mon May 18 2026

Today through Tuesday:

The nrn portion of the QLCS over ne IA and se MN has recently produced severe wind gusts but gradual weakening is expected as it moves into greater CIN. Farther to the south, the gust front is outrunning the convection but sporadic wind gusts of 40-50 mph are still occurring. For srn WI, gusty winds and scattered storms will continue to initiate along and behind the gust front during the early morning hours. MUCAPE of 1500-2000 J/KG will be present but with high LFCs at 650-700 MB. The high LFCs should aid in the further dissipation of the organized line and/or transitioning to elevated scattered storms.

During this time, a wave of low pressure will track across MN to wrn Lake Superior and be the catalyst to shifting the warm front nwd into central WI. Thus the low stratus and areas of fog toward central WI will come to an end during the early morning hours. Some showers and storms will likely linger through later this morning, but capping will set in again and will aid in some scattering of clouds and temps nearing 80F for the afternoon.

Another wave of low pressure will develop from the central Great Plains to nrn WI from late Mon afternoon until 12Z Tue, while the main shortwave trough tracks from the central Rockies to nw WI. The actual trailing cold front will likely not pass until Tue, but there is some confidence in another round of showers and storms for mainly after midnight (early Tue AM) as another MCS moves into srn WI from the west. The MCS may already have reached the dissipating stage at this time, but there is uncertainty with the timing of the evolution. Once again, damaging wind gusts would be the main concern. Finally, there may be some shower and storm development with the cold frontal passage Tue afternoon with severe probs are low at this time.

Gehring

LONG TERM

Issued 1200 AM CDT Mon May 18 2026

Tuesday night through Sunday:

Gusty northwest winds remain in place through Tuesday night as high pressure builds in from the northwest. Winds gradually diminish into Wednesday as high pressure settles into the region. Temperatures are expected to be back into the 60s and low 70s for highs and lows in the upper 30s to mid 40s through midweek. High pressure remains dominant through Thursday before propagating eastward into the Northeast U.S. Low pressure will begin to deepen in the lee of the Colorado Rockies, ejecting into the Plains Friday morning. With high pressure remaining over the Northeast, models are indicating a split low progression, with one portion of upper level energy propagating through the Lower Mississippi Valley along a Gulf humidity axis, and the other portion following the long wave pattern northeastward into the western Great Lakes. A few showers and thunderstorms may work their way in as early as Thursday night into Friday (15-25%), with more potential for widespread showers and thunderstorms into Friday night and Saturday as the cold front from the Midwest low phases with the southern low. Confidence in timing and placement remains in question due to model discrepancies, so maintained NBM probabilities for this update. Precipitation exits Saturday night as ridging begins to build back into the southern Wisconsin from the central Plains. Expect temperatures to return to the upper 70s and low 80s Sunday as winds shift to southerly, with additional chances for storms Sunday night into Monday.

MH

AVIATION

Issued 1200 AM CDT Mon May 18 2026

Stratus below 1 kft and areas of fog are occurring toward central WI, but VFR conditions will return early this morning once the warm front passes to the north. Scattered thunderstorms with gusty winds will then move across much of srn WI during the early morning hours with some showers and storms continuing through late this morning. Sct-bkn040-060 clouds are expected during this time but areas of MVFR Cigs may occur. Another round of thunderstorms and gusty winds is then forecast late tnt with more MVFR Cigs possible.

Gehring

MARINE

Issued 1200 AM CDT Mon May 18 2026

A warm front will move from southern Lake Michigan to northern Lake Michigan this morning. East to northeast winds will become breezy out of the south. Areas of dense fog may occur at times until the front passes. Breezy south winds will then continue through today into Tuesday followed by a wind shift to the northwest late Tuesday afternoon and evening with the passage of a cold front. High pressure and light and variable winds will then take hold from late Wednesday into Thursday.

A Marine Dense Fog Advisory is in effect from Sheboygan to North Point Lighthouse until 3 AM CDT today. The fog will dissipate once the warm front moves to the north, and south winds and milder temperatures arrive.

Gehring

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Dense Fog Advisory...LMZ643-LMZ644 until 3 AM Monday.