textproduct: Milwaukee/Sullivan

KEY MESSAGES

- There are chances (20 to 40 percent) for rain showers at times tonight through Thursday. There could be a few rumbles of thunder with the showers Wednesday afternoon.

- Cooler temperatures are expected through the end of the week. Areas of frost are possible each night Wednesday night through Friday night.

UPDATE

Issued 636 PM CDT Tue Apr 28 2026

Middle to high clouds will continue to push northeast through the area at times tonight into Wednesday. Winds will weaken this evening and become northwest, shifting northeast later tonight toward Lake Michigan as a backdoor cold front shifts southward. Winds will increase from the northwest to north on Wednesday, with a northeast turn in the afternoon near Lake Michigan.

There will be small chances (around 20 to 30 percent) for showers to occur later this evening into the overnight hours, as some frontogenesis response in the 850 mb to 700 mb layer moves through with some differential CVA aloft from a passing shortwave trough.

The shower chances (20 to 40 percent) linger into Wednesday, as another vorticity maximum rotates with a more elongated 500 mb trough through the region. This will bring more differential CVA, along with some weak instability with daytime heating. Left small (around 20 percent) chances for thunder in the afternoon, as there may be enough low level CAPE reaching the -10 degree Celsius level to bring some rumbles of thunder.

Lows tonight should drop into the middle 40s, with highs Wednesday in the middle to upper 50s inland, with 40s to lower 50s closer to the lakeshore.

Wood

SHORT TERM

Issued 138 PM CDT Tue Apr 28 2026

Tonight through Wednesday night:

A pair of shortwaves will move through tonight and again during the day Wednesday, bringing a chance for showers to southern Wisconsin. The showers this evening into early tonight look mainly tied to some better frontogenesis, focusing primarily south of I-94. Could be some light showers then across the forecast area overnight as the wave move though. Another wave will bring showers from late morning Wed into the evening, and will be largely diurnally driven. Given decent low level lapse rates and a little bit instability (~250 j/kg or less), wouldn't be surprised by a rumble or two of thunder during the day tomorrow.

Temps will be a little cooler tomorrow, with highs in the low 50s near the lake under onshore winds and mid 50s inland. Temps tomorrow night could drop far enough for some frost by late in the night if skies clear out enough.

DDV

LONG TERM

Issued 138 PM CDT Tue Apr 28 2026

Thursday through Tuesday:

A round of showers will be possible again on Thursday, as another shortwave rotates around the broad upper low centered just north of Lake Huron. These will largely be driven by daytime heating, so late morning into early evening will be the best chance (20-40%) for showers. Could see a similar set up on Friday, though models appear a bit drier late in the week as surface high pressure gradually moves in from from the northwest.

Temps will be below normal through late week under the northwest flow, with frost possible each night Wednesday night through Friday night.

The upper low will finally pull away from the region over the weekend, with the surface high becoming more centered over the region. Dry weather is thus expected Sat and Sun. Temperatures should also begin to warm back up, with highs near normal by Sunday.

DDV

AVIATION

Issued 636 PM CDT Tue Apr 28 2026

Middle to high clouds will continue to push northeast through the area at times tonight into Wednesday. Winds will weaken this evening and become northwest, shifting northeast later tonight toward Lake Michigan as a backdoor cold front shifts southward. Winds will increase from the northwest to north on Wednesday, with a northeast turn in the afternoon for terminals near Lake Michigan.

There will be small chances (around 20 to 30 percent) for showers to occur later this evening into the overnight hours. The shower chances (20 to 40 percent) linger into Wednesday, with a few rumbles of thunder possible Wednesday afternoon. For now, left out mention of showers in the TAFs, but may bring in some PROB30 groups for showers in later forecasts.

Wood

MARINE

Issued 636 PM CDT Tue Apr 28 2026

High pressure of 30.2 inches centered just north of the Dakotas will gradually shift southeastward into the region through the end of the week. Breezy westerly winds will transition to light (5 to 15 knot) northerly winds for tonight through the remainder of the week, as this high approaches. Light showers will be possible at times through the rest of the week, as weak shortwaves roll through.

DDV/Wood

MKX WATCHES/WARNINGS/ADVISORIES

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