textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Scattered showers and thunderstorms may develop and shift through portions of the area this evening into tonight, mainly from 8-9 PM CDT this evening to around 1-3 AM CDT Tuesday. If storms develop, they could become severe, with large hail up to ping pong ball size being the primary hazard. Uncertainty remains with storm coverage and location.

- Additional showers and storms are forecast Tuesday morning and afternoon, with exact areas of development depending on early day clouds/rain and frontal timing. A few storms could be severe, with large hail and gusty winds being the primary threats.

- Increasing potential for snow, sleet and freezing rain along and north of Interstate 94 Wednesday evening into Thursday morning. Impacts to the Wednesday evening and Thursday morning commutes possible.

- Additional chances for rain and a few thunderstorms Friday afternoon into Saturday.

UPDATE

Issued 751 PM CDT Mon Mar 30 2026

The front that extends from north of the Dells to Juneau, then southeast to between Racine and Kenosha, may continue to slowly slide to the southwest this evening before stalling. Meanwhile, a modest shortwave trough should move east across northern Iowa into southern Wisconsin this evening into the overnight hours, with a surface trough pushing east ahead of it. This may be the focus for initial showers and storms to develop in northern Iowa this evening, which may push into southern Wisconsin later this evening into the overnight hours.

The main window would be 01Z-02Z to 06Z-08Z Tuesday for convection in the area, perhaps lingering a bit longer. The surface frontal boundary across the area should serve to help focus upward motion. The low level jet may become more west southwest this evening, which may provide some additional focus for upward motion.

Forecast soundings and SPC Mesoanalysis are showing steep lapse rates aloft with plenty of elevated CAPE (over 1500 J/kg) with effective shear of 40 to 50 knots or more. Thus, if any storms can get going in this environment, large hail up to ping pong ball size in diameter is possible. Some strong winds may occur as well.

CAMs have not been consistent with what may occur into the overnight hours, so there is some uncertainty to where the convection may develop and move through. Forecast soundings are also showing somewhat of a capping inversion at 850 mb, which may limit the amount of storms that develop. So, some uncertainty remains with storm coverage and location.

There may be more elevated showers and storms that develop toward daybreak Tuesday morning, as the low level jet becomes more southwesterly and refocuses over southwest Wisconsin into northeast Iowa. If this activity develops, it would have some large hail potential as well. If this lingers into Tuesday morning, this could limit instability and further development with the cold frontal passage Tuesday afternoon.

Wood

SHORT TERM

Issued 230 PM CDT Mon Mar 30 2026

Rest of Today through Tuesday night:

Two frontal zones are beginning to take shape across southern WI at the moment, and are slowly morphing into one. The first is a stalled warm front spanning from roughly Montello to West Bend, and the second is a lake-breeze front from West Bend to Milwaukee to the shoreline of Kenosha county. South and west of these boundaries, we have southwesterly surface flow advecting warmer air and dewpoints in the 50s into the area. North and east of the boundaries, lake-refrigerated air is holding it's ground. Meanwhile (as of 230 pm CDT), in eastern Nebraska we can see a shortwave trough lifting northeastward towards our region, with ACCAS clouds visible on GOES satellite imagery. This perturbation will serve as the focal point for thunderstorm activity when it reaches our region this evening (mainly after 8pm CDT). CAMs are all over the place when it comes to the location of convective initiation, with models like the NAM 3k preferring a surface frontal-based initiation towards central WI later in the evening, and the HRRR firing precipitation from the ACCAS in northeastern IA earlier in the evening which would allow storm-scale dynamics to take over and track storms towards far southern WI. With the wide range of CAM solutions, it's too early to advertise a 'threat area' for this evening's convection, but in any case, a fraction of the CWA is likely to see scattered thunderstorms this evening.

Ingredients are present this evening through tonight for a few strong to severe storms with hail up to 1.5 inches in diameter (level 2 out of 5 severe threat). Roughly 1,000 to 1,500 joules MUCAPE and 850-500 mb Lapse Rates in excess of 8 C/km are expected with this evening's convection, with the LLJ likely to rapidly replenish these values after the initial wave of convection. Hence, though many CAMs resolve a several hour long lull in convection late tonight into early Tuesday morning, we certainly can't pin down when (or if) this lull would occur, and an additional severe storm later tonight into Tuesday cannot be ruled out.

Additional showers and thunderstorm chances continue into Tuesday morning with this same activity, with the MUCAPE values gradually diminishing later in the morning (severe threat decreases to level 1 out of 5 post-dawn Tuesday). The aforementioned frontal boundary will sag southward across the region at some point later Tuesday morning through early Tuesday afternoon, with areas along and just behind this front becoming a focal point for additional organized storms, with hail as the primary threat, and some gusty winds as a far secondary concern. Timing of any morning convection will determine the potential for airmass recovery in advance of the front, thus determining the exact risk level & timing. Any lingering showers / weak storms should be confined south of or near to the WI/IL border by Tuesday evening, leaving predominantly dry weather for our region Tuesday night.

Sheppard

LONG TERM

Issued 230 PM CDT Mon Mar 30 2026

Wednesday through Monday:

An active mid week and weekend ahead for Southern Wisconsin. The first "round" of precipitation comes late Wednesday through Thursday. Then a second "round" will follow quickly behind for late Friday through Saturday. Then some quieter conditions look to move in for Sunday and Monday.

Kicking things off with the first round, there will be a low pressure system that develops in the central and southern Plains Tuesday and then advects toward the Great Lakes Region for Wednesday evening into Thursday Evening. There is fairly good consensus on from 500 mb to the surface that this shortwave will move northeast into the region. The one question on track that remains is will this pass just to the south of the state, through northern Wisconsin or somewhere in between. There is a lot of variability between the deterministic and ensemble members. The track will be very important in regards to the potential for mixed precipitation.

A track through southern Wisconsin (which looks the most likely with this model run), would start out with southwest winds WAA and the LLJ moving into the area. This would result in a large area/deep area of above freezing temperatures and dewpoints in forecast soundings. This will kick precip type off with mostly rain. As temperatures cool overnight, both at the surface and aloft, the concern for mixed precipitation grows. The best chances for freezing rain, sleet and snow will be for areas north of Interstate 94 with this track. Since there is a lot of variability, CAN deterministic is much further north which favors more rain should the sfc low fallow a similar path. This would shorten the window of cooler temps overnight and limit how cold it gets which will leave precip types in the rain and freezing rain department (mostly rain). A more southward track, deterministic GFS and few ensemble runs from the same model set favor more snow and sleet. Snow chance would extend further south toward the WI/IL border in this scenario as well. Make sure to keep up to date with the forecast for this mid week system as confidence is high on the chances for precipitation (70-95% chance), but the fluctuation in precipitation type be a big determining factor on the expected impacts. Wednesday evening and Thursday morning commutes are the most likely to see impacts.

The next "round" of precipitation will come Friday evening through Saturday as another upper level trough and sfc low move toward Wisconsin from the Rockies. Temperatures overall are trending warmer than the midweek system (based on the low track), which will bring chances for rain and thunderstorms (60 to 80% chance). If the low tracks further south there could be some changes to the precipitation type, but overall guidance is trending warmer. This is further supported by the dipole pattern for 500 mb Cluster Analysis. The dipole distribution supports uncertainty in the timing and location of the trough.

Beyond this system high pressure looks to build into the Great Lakes Region for Sunday and Monday which will bring much quieter and near normal temperatures for the start of the week.

Patterson

AVIATION

Issued 751 PM CDT Mon Mar 30 2026

The front that extends from north of the Dells to Juneau, then southeast to between Racine and Kenosha, may continue to slowly slide to the southwest this evening before stalling. East to northeast winds are expected toward Sheboygan this evening, with gusty south winds toward Madison and Janesville. These may linger into later tonight, before winds become southwest toward Kenosha Tuesday morning and shift northwest behind a cold front as the day goes on.

There should be a period of low level wind shear conditions tonight for Janesville and Kenosha, perhaps Madison, Waukesha and Milwaukee as well, tonight as south southwest winds around 40 knots develops at 2000 feet AGL.

Showers and some storms may move trough the area from 01Z-02Z to 06Z-08Z Tuesday, perhaps lingering a bit longer. The surface frontal boundary across the area should serve to help focus this development. If any storms develop, large hail could be possible, along with some gusty winds. There is uncertainty with storm coverage and timing. VFR ceilings should prevail, though local MVFR/IFR ceilings and visibility may occur with any storms.

There may be more elevated showers and storms that develop toward daybreak Tuesday morning. If this activity develops, it would have some large hail potential as well. If this lingers into Tuesday morning, this could limit instability and further storm development with the cold frontal passage Tuesday afternoon. Ceilings should drop to around or below 1000 feet AGL Tuesday morning, lingering into the afternoon ahead of the cold front. Visibility with any showers and storms should be 2 to 5 miles, locally lower at times. Conditions should return to VFR category after the front moves through.

Wood

MARINE

Issued 230 PM CDT Mon Mar 30 2026

A frontal zone will sharpen over Lake Michigan today, with north to northeasterly flow over northern portions of the lake and southerly flow further south. The boundary between these two wind patterns has setup along a Sheboygan WI to Manistee MI line early this afternoon, but should sag south to a Milwaukee WI to Whitehall MI line into this evening (approximately), with both wind flows becoming stronger far north and far south of the boundary. Some 20 to 30 kt gusts may occur over the northern and southern thirds of the lake this evening into tonight as the boundary sharpens. Rounds of showers and thunderstorms are expected tonight into Tuesday across the lake, with a few stronger storms possible at times (particularly near the frontal boundary). Large hail would be the primary threat with any stronger storms.

The boundary sags further south as a cold front Tuesday afternoon, focusing lingering shower and thunderstorm activity over southern Lake MI before washing it away later Tuesday. Gusty north winds build in behind the front Tuesday evening into Wednesday, with 20 to 30 kt gusts. Winds veer northeasterly through Wednesday.

30.7 inch high pressure will shift from Ontario to Quebec through the late week time period as 29.7 inch low pressure approaches from the southwest, allowing winds to trend east-northeasterly. Will need to watch for gale potential later this week (particularly Thursday) as the low pressure system approaches the lake.

Nearshore Zones: The wind fields well north and well south of the aforementioned frontal zones (tonight through Tuesday night) may occasionally lead to Small Craft Advisory level winds and waves, as well as sudden shifts in wind direction. Small Craft Advisories and Marine Weather Statements may be needed. Strong to severe thunderstorms are possible Tonight into Tuesday, with hail as the primary threat. Stay tuned in case a Special Marine Warnings become necessary.

Potential for Advisory-level wind gusts and waves lingers through the rest of the forecast period as well.

Sheppard

MKX WATCHES/WARNINGS/ADVISORIES

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