textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Periods of showers and storms (60-90 percent chance) expected through tonight. There is a Marginal Risk for severe storms mainly for damaging winds. Can't rule out isolated large hail or a brief tornado across southwestern Wisconsin.

- Showers are expected to redevelop on Friday especially over the ern half of WI. Isolated storms still possible.

- Dry weather with highs in the 60s this weekend; cooler by Lake Michigan due to light easterly winds.

- Widespread showers (80-90 percent chance) and isolated thunderstorms return late Sunday night through Monday night. Chances are fairly high for an inch of rainfall.

SHORT TERM

Issued 1111 PM CDT Thu Apr 23 2026

Tonight through Friday night:

The line of storms is has just moved into southern Wisconsin here this evening. Storms continue to move north northeast along a line stretch from roughly the UP of MI through La Crosse into eastern IA and back down to MO. MUCAPE, SBCAPE and the effective shear are all on a downward trend here this evening as this line of storms moves into a much weaker environmental set up. MUCAPE is hovering around 500 J/kg with SBCAPE around 100 J/kg. Shear is not much better around 20-30 kts at best. The scattered storms that developed ahead of the line earlier in the night have since merged with the line which did add in some higher reflectivities for a bit, but this has since subsided.

Can't rule out a few stronger storms yet this evening. Until we lose out SBCAPE the potential for a brief spin up still exists but this chance is incredible small. Its more likely that strong winds and heavy rain are the primary threat at this point. This is especially true as the line of storms become more outflow dominant over time. The window for any brief spins ups will be over the next hour or so. The mid level lapse rates are slowly coming down which will favor heavy rain as the night drags on. Give the slow storm motion and current training given the storm motion (near perpendicular to the line at this point), urban and small stream impacts are growing. This line of rain and storms is still expected to weak becoming more broken with scattered to isolated storms expected. Once this happens the flooding threat will diminish.

The cold front will slowly move down the state late tonight into Friday morning bringing an end to any lingering showers through the early morning hours. Severe weather is not anticipated through Friday morning. A few rumbles of thunder will be the primary concerns by this point. As winds turn to northwesterly behind the front slightly cooler and drier conditions will move into the state. Given the timing of the cold front, temperatures may still make it into the 60s Friday. High pressure will then slowly build into the region Friday night into Saturday.

Patterson

LONG TERM

Issued 1111 PM CDT Thu Apr 23 2026

Saturday through Thursday:

Looking dry and quiet pattern across southern WI through the weekend as our neck of the woods sits in between low pressures in the Canadian Plains and Central Plains while high pressure meanders to the northeast east of the Great Lakes. This pattern will result in more season temps, but easterly flow off of Lake Michigan will help keep things cooler along the lakeshore.

A more active pattern is taking shape for the start of next week as an upper-level ridge axis pushes across the region bringing in increasing low-level WAA later Sunday into Monday while an upper- level trough digs across the Rockies and across the Plains. While there is agreement on this upper-level trough lifting across the Midwest for the start of next week, there continues to be variations of solutions in the ensembles when it comes to timing and track of the surface low associated with the upper-level wave. EPS is favoring a more northward track while GEFS is a bit more south. Depending of where this low tracks along with where the warm front lifts/sets up will play a role in any stronger storm potential. Otherwise, at this time expect at least increased PoPs for the start of next week.

Then looking at a cooler pattern with potentially below normal temps toward the middle of next week as the upper-level trough meanders over the Central CONUS with high pressure bringing in the cooler Canadian airmass through the end of the week.

Wagner

AVIATION

Issued 1111 PM CDT Thu Apr 23 2026

VFR to IFR conditions are possible through the period. Upper level clouds are slowly building in from the west this evening as a cold front approaches from western IA and MN. As rain and thunderstorms move in late this evening into tonight, ceilings are expected to fall to around 1-3 kft. The lower ceilings are expected to be with any of the rain that moves through. As the rain becomes more scattered to isolated overnight, ceilings could jump around a bit between IFR to MVFR until roughly 9Z. Then MVFR cigs should spread across southern Wisconsin and remain through the rest of the morning. Visibilities around 2-4 SM will also be possible through the overnight hours with any storm/rain. Heavy rain will be possible which could drop visibilites a bit lower at times (about 1 SM). Rain showers will linger into Friday morning as the cold front exits to the east. Ceilings will improve back to VFR from west to east through he morning and afternoon hours.

Breezy south to southeast winds this evening will weaken slightly tonight and loose their gusts. The cold front will pass early Friday morning into early Friday afternoon turning winds to the northwest. By Friday night, the winds will weak further and become northerly winds will continue to slowly turn becoming easterly by Saturday night.

Patterson

MARINE

Issued 1111 PM CDT Thu Apr 23 2026

Areas of fog are likely to continue over the lake into Friday due to the mild, moist air flowing over the colder water of the lake. This fog and mild air will be along modest south to southeast winds. A warm front will stall across the far northern edge of the lake failing to reach the UP of Michigan. This will create a tighter pressure gradient just north of the front and will result in winds approaching gales across the narrow area. An occasional gale force gust will be possible until the low pressure system around 29.2 inches and an associated cold front pass the lake Friday afternoon/evening. A few thunderstorms will be possible across the lake until the cold front clear to the east. Severe weather is not anticipated at this time.

Light north winds on Saturday will then become easterly Saturday night and Sunday before increasing into Monday. 29.4 inch low pressure is forecast to track northeastward from the central Great Plains (Sunday night) near or over Lake Michigan (Monday night), with gusty east to southeast winds ahead of its arrival and gusty west winds behind it (into Tuesday). Not seeing widespread gale potential with this system, though trends will be monitored.

A Small Craft Advisory remains in effect through early Friday afternoon north of Port Washington for building waves.

Patterson

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643 until 1 PM Friday.