textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Isolated to scattered thunderstorms are possible late this afternoon(10-20% Chance) and evening and again Friday evening (30-50% Chance).

- Additional shower chances return on Sunday (40-60%).

SHORT TERM

Issued 245 PM CDT Thu Jun 18 2026

Tonight and Friday:

Partly cloudy skies and dry weather early this afternoon may give way to some light rain showers later this evening. The sfc low pressure continue to move east with a mid level shortwave lagging behind a bit this evening. The last of this mid level lift combined with some mid level moisture should give there state just enough lift to get isolated to scattered rain showers. Chance for these showers late afternoon through the evening are around 20%. There are already a few showers developing across southeastern MN and western UP of Michigan. Shear isn't great and instability isn't much better across southern Wisconsin so lightning or any storms are not expected. As the sun goes down and the mid level shortwave pulls to the east, rain chances will end and skies should become mostly clear.

For Friday, mostly dry weather is expected into the afternoon ahead of another approaching mid level shortwave. This shortwave looks to have better instability and shear in the low level to support thunderstorms. The better chance for stronger storms will largely be to our north in west central Wisconsin and Minnesota, where the better instability and lift looks to reside. The northwestern corner of the MKX forecast area including Sauk, northwest Columbia and Marquette County have the best chances for seeing any strong storms. Main hazards with any strong storms are expected to be brief gusty winds and lightning. As storms move southeast overtime they are expected to weaken, which will make sporadic lightning the largest concern for southeastern Wisconsin.

Patterson

LONG TERM

Issued 245 PM CDT Thu Jun 18 2026

Saturday through Thursday:

As low pressure exits to the east Saturday morning, dry conditions and northwesterly breezes will bring in temperatures in the mid to upper 70s. A weak cold front stalling across northern Illinois Saturday night into Sunday will phase with a deepening ejecting low pressure system from the central Plains. Northeasterly winds will increase through the day as low pressure approaches from the south, keeping southern WI on the cool side (low 70s to upper 60s), and keeping any severe potential at bay. Rain will spread northeastward through Sunday into Sunday night as low pressure makes its closest approach through northern Illinois. Northern extent of rainfall will depend on exact track of the low, so probabilities are lower toward central WI (~30% chance) and higher toward IL (60-70%). Precipitation tapers off overnight as low pressure propagates into the Northeast U.S., with strong high pressure pushing into the Midwest and keeping WI dry through Monday night.

Pattern becomes much more complex Tuesday through Thursday, with impulses from the Gulf Coast and the northern High Plains interacting with each other to produce precipitation chances across the Mississippi Valley into the Upper Midwest. Highest confidence is in Wednesday afternoon (PoPs 40-60%) as the northern High Plains low propagates through the Upper Midwest, but prefrontal convection and shortwaves will produce on and off thunderstorms across the region throughout the timeframe (PoPs of 20-40% for most timeframes).

MH

AVIATION

Issued 245 PM CDT Thu Jun 18 2026

Largely VFR conditions through the period. Diurnal cumulus clouds are expected to remain through sunset across Wisconsin. These clouds are expected to be few to scattered around 3-6 kft. Isolated to scattered rain showers are expected to develop and move southeast across southern Wisconsin this evening. With the low coverage and confidence in rain kept mentions out of the TAFs. Mostly clear skies are expected tonight with more diurnal cumulus clouds expected to develop Friday afternoon/evening. Rain and thunderstorms will be possible Friday evening into Friday night.

Northwest winds will be breezy at times through this afternoon with gusts around 20 kts(23MPH) possible. Winds will diminish this evening becoming light and variable tonight. Light northwest winds Friday morning will become westerly by the afternoon. A Lake breeze looks to try to move inland late Friday afternoon into the evening. There is uncertainty on if this will move far enough inland to turn wind direction to easterly at the lakeshore terminals.

Patterson

MARINE

Issued 245 PM CDT Thu Jun 18 2026

As low pressure of 29.3 inches in northern Michigan will move northeast into eastern Quebec today. Winds will shift to northwesterly and diminish as this low pressure exits. High pressure around 30.0 inches will build into the mid Mississippi valley behind the exiting low, keeping northwest winds light through Friday. Winds may briefly turn southwesterly Friday night as weak low pressure around 29.9 inches moves through the region, but high pressure will rapidly regain dominance by Saturday, keeping winds light and variable. Stronger low pressure will approach from the central Plains on Sunday, bringing more widespread rain and thunderstorms and turning winds to northeasterly. Northeast winds will continue into early next week.

Patterson

MKX WATCHES/WARNINGS/ADVISORIES

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