textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Scattered thunderstorms early this morning, then more widespread showers and storms later this morning into the afternoon. Severe storms are not anticipated, but possibly small hail with the stronger storms.

- More rounds of showers and storms late tonight into Mon then again late Mon nt into Tue, but much uncertainty for severe storms given the morning timing of potential MCSs.

- Cool and drier weather then returns for Wed-Thu.

SHORT TERM

Issued 1223 AM CDT Sat May 16 2026

Tonight through Tuesday night:

The dry cold front is currently accelerating down Lake MI and will arrive in the Sheboygan area around 1 AM CDT and MKE around 4 AM CDT. Farther to the southwest, a west to east line of slow moving thunderstorms extends from ne IA into sw WI, probably triggered by elevated warm, moist advection. A sswly low level jet of 35-40 kt is expected to develop over ern IA and nose into far srn WI toward 10Z so expect scattered storms to develop over the area. MUCAPE of 1000-1500 J/KG near the IL border will slowly drift nwd during the overnight, but lapse rates will weaken resulting in MUCAPE falling below 500 J/KG. Still expecting small hail within the stronger storms tnt.

Otherwise, more widespread showers and storms are expected from Sun AM into the early to mid afternoon when 850-700 mb warm, moist advection and a MCV moves through the region. The MCV will develop from the severe convection over srn IA and nrn MO tnt and lift newd into srn WI after 12Z. The remnants of the showers and storms from NE to srn IA and nrn MO may accompany the MCV or new development will occur given the aforementioned warm, moist advection. The mid level lapse rates will drop to 5.5-6.0 C/KM during this time so elevated CAPE will remain marginal with perhaps small hail with the stronger storms. The sfc warm front will not reach a line from Madison to Kenosha until late afternoon but temps will quickly warm to near 80F once it passes. High temps toward central WI should only reach into the 60s with 50 and 60s at the Lake MI shoreline.

A wave of low pressure will then track from ern NE to nw WI by 12Z Mon, while a decaying MCS from srn MN and IA may be arriving after 09Z Mon over south central WI. The wave of low pressure will weaken as it tracks newd across Lake Superior into Ontario during the day, but will aid in continued warm, moist advection over srn WI. A MCV may also be present within the decaying MCS, and will forecast 60-70 percent chances for showers and sct storms. The severe storm potential is very uncertain given the morning arrival of showers and storms and there may be a lack of forcing later in the afternoon.

Another wave of low pressure will develop from the central Great Plains to nrn WI by 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 Mon nt-Tue AM given srn WI remains downstream of areas of new convective initiation and possible MCSs. The potential for severe storms is very uncertain given the morning timing.

Gehring

LONG TERM

Issued 1223 AM CDT Sat May 16 2026

Wednesday through Saturday:

High pressure and a cooler air mass will follow for Wed-Thu with lgt sly winds and warm advection returning late Thu into Sat as the high moves ewd and a shortwave trough approaches from the west. Thus high temps in the 60s for Wed-Thu will return to the 70s well inland from Lake MI for Fri, then 70s over all of srn WI on Sat. A slight chance for showers is forecast Fri nt-Sat.

Gehring

AVIATION

Issued 1223 AM CDT Sat May 16 2026

VFR conditions early this morning but scattered storms are expected over far srn WI. The showers and storms will then become more widespread for later this morning into the early to mid afternoon. MVFR Cigs will develop later this morning and continue into much of the afternoon. VFR conditions will return over much of srn WI by late afternoon and evening, but MVFR Cigs may linger over central WI. IFR Cigs may occur late this afternoon and evening over east central WI, especially near Lake MI. LLWS via a swly low level jet of 45 kt is expected to develop tnt.

Gehring

MARINE

Issued 1223 AM CDT Sat May 16 2026

A cold front over central Lake Michigan early this morning will track to far southern Lake Michigan by daybreak. A wind shift to the northeast is expected along with brief gusty winds. The front will then gradually return north as a warm front mainly tonight, with winds veering southerly and becoming gusty. Areas of fog may form later today and evening as the front moves northward. Breezy south winds will then continue 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 Small Craft Advisory may be needed from Sheboygan to Winthrop Harbor for Mon-Tue due to persistent and gusty south winds and high waves.

Gehring

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...None.