textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Scattered high-based showers and a few storms will continue to push east with the cold frontal passage into early this evening, exiting over Lake Michigan by early evening. Gusty winds up to 45 MPH may occur with any of the showers, due to dry air helping to accelerate any rain/wind downward.

- Cooler temperatures are expected for the rest of the week.

- Frost may occur toward the middle to later portions of the week.

UPDATE

Issued 642 PM CDT Mon May 4 2026

Scattered high-based showers and a few storms will continue to push east with the cold frontal passage into early this evening, exiting over Lake Michigan by early evening. Gusty winds up to 45 MPH may occur with any of the showers, due to dry air helping to accelerate any rain/wind downward. DCAPE values are up to around 900 J/kg over areas ahead of the cold front, which are helping mix down gusty winds aloft.

Winds will shift to the west and northwest behind the frontal passage this evening, with the gusts subsiding and winds weakening overnight. The middle to high clouds should linger overnight and into Tuesday morning in southern/southeastern portions of the area, where some 700 mb to 500 mb frontogenesis response may remain. This may bring some sprinkles or brief light showers overnight. Lows should drop into the upper 30s northwest to the middle 40s far south and southeast.

Diurnal stratocumulus clouds may develop in the late morning into the afternoon on Tuesday around 7000 feet AGL, with forecast soundings showing some moisture in this area. Modest west northwest winds are expected, with a lake breeze possible later in the day. Cooler highs should reach into the middle 50s.

Wood

SHORT TERM

Issued 155 PM CDT Mon May 4 2026

Tonight through Tuesday night:

Gusty southwest winds up to 40 mph, large dew point depressions around 30 degrees, and high temperatures in the mid to upper 70s will support elevated fire weather conditions. See the fire weather section for more details.

A cold front is expected to move over the area between 3pm and 10pm this afternoon and evening. The boundary layer remains well mixed this afternoon, with large dewpoint depressions near 35 degrees in the low levels. Some moisture advection may occur over south central and southeast WI ahead of the front late this afternoon, but the Tdds will still be around 25, and storms will remain high based.

CAMs have suggested that widely scattered storms will form along the front over south central WI between 5pm and 7pm this evening and then track southeast with time, generally losing strength as skinny CAPE profiles supporting ~500 J/kg SBCAPE likely get utilized/entrained fairly quickly. Given the dry low levels, a high plains-like environment is present, which may support gusty winds with any storms that develop as rain evaporates into the dry low-level environment. Small hail can't be ruled out as well, as mid level lapse rates are steep at around 7 C/km. The skinny CAPE will limit hail size however.

The front is expected to clear tonight, with some low end potential (15 to 20% PoPs) for light, post-frontal showers and sprinkles through dawn on Tuesday.

Otherwise quiet, cooler, and dry on Wednesday with highs in mid to upper 50s. High cloud cover will linger through the day due to the lingering effects of the front to our south over Illinois. Areas of frost are then possible Tuesday night into Wednesday along the Kettle Moraine.

CMiller

LONG TERM

Issued 215 PM CDT Mon May 4 2026

Wednesday through Monday:

Cool conditions persist Wednesday and Thursday as troughing remains over the region aloft. More widespread frost is possible area-wide Wednesday night into Thursday. Shower activity is then expected Thursday as the base of the trough pivots through the area. The combination of PVA and steep lapse rates may support shallow convection capable of pea-sized hail.

Warming is then anticipated Friday through Sunday as warm advection occurs over the region. Some WAA driven showers may occur during the afternoon, with then relatively quiet conditions Saturday. Saturday night into Sunday, another wave of mid level warm advection and a sfc trough will support more showers, with things then largely drying out late Sunday into Monday.

CMiller

AVIATION

Issued 642 PM CDT Mon May 4 2026

Scattered high-based showers and a few storms will continue to push east with the cold frontal passage into early this evening, exiting over Lake Michigan by early evening. Gusty winds up to 45 MPH may occur with any of the showers.

Winds will shift to the west and northwest behind the frontal passage this evening, with the gusts subsiding and winds weakening overnight. The middle to high clouds should linger overnight and into Tuesday morning in southern/southeastern portions of the area. This may bring some sprinkles or brief light showers overnight.

Diurnal clouds may develop in the late morning into the afternoon on Tuesday around 7000 feet AGL. Modest west northwest winds are expected, with a lake breeze possible later in the day.

Wood

MARINE

Issued 642 PM CDT Mon May 4 2026

A Small Craft Advisory remains in effect until 7 PM CDT this evening, for gusty southwest winds. The gusty southwest winds will linger until around this time, ahead of an approaching cold front. The cold front is in association with low pressure of 28.9 inches over north central Ontario, which will track northeast toward James Bay through Tuesday.

As this occurs, the cold front will sink southeast over Lake Michigan through this evening and clear the lake tonight, shifting winds to northwesterly. Scattered showers and storms along the front may produce gusty winds up to 40 knots over the lake.

West to northwest winds then persist through the first half of Tuesday. Winds will become light and variable Tuesday afternoon into Wednesday morning, as a weak surface ridge passes over the lake. Similar winds are expected Wednesday, before southerly return Thursday.

CMiller/Wood

FIRE WEATHER

Issued 642 PM CDT Mon May 4 2026

The Special Weather Statement for the elevated fire weather conditions will be allowed to expire at 7 PM CDT this evening, as winds shift to the west northwest behind the cold front and slowly weaken. Very low relative humidity values of 23 to 31 percent will linger into early evening as well.

Additional dry conditions may occur again tomorrow, owing primarily low minimum relative humidity values between 25 and 35 percent. However, temperatures will be cooler in the 50s, winds will be lighter, and there will be more cloud cover present. So, not expecting elevated fire weather conditions on Tuesday.

Kuroski/CMiller/Wood

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 7 PM Monday.