textproduct: Milwaukee/Sullivan

KEY MESSAGES

- A Winter Weather Advisory is in effect for counties north of Interstate 94 for ice accretions from freezing rain. 0.1 to 0.2 inches of ice accretion is expected, mainly on elevated and untreated surfaces. Travel impacts to the Thursday morning commute are expected. - Thunderstorms are expected Thursday into Thursday night. Strong to severe storms are expected during the afternoon into the evening. A Slight Risk for severe weather exists north of Interstate 94, and an Enhanced Risk exists along and south of Interstate 94. All severe weather hazards will be possible.

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

- Easterly to southerly wind gusts will reach gale force over the northern two thirds of the lake. A Gale Warning is in effect Thursday into Thursday night.

UPDATE

Issued 809 PM CDT Wed Apr 1 2026

The rain that we are waiting for this evening is currently over north central and east central Iowa which is along an axis of 850mb frontogenesis. There is a decent slope to it from 850 to 700mb which hints at widespread warm air advection and isentropic lift, and is conducive for widespread precip. The precip is still on track to spread into south central WI between 10 and midnight, and into southeast and east central WI between midnight and 3 AM.

Southern WI still has a lot of dry air at the surface, but this precip moving in will not take long to overcome that. The precip will likely remain all rain south of Lone Rock to Madison to Milwaukee. We are keeping a close eye on temperatures north of this line, as dewpoints in the 20s will help temperatures that are currently in the lower to mid 30s drop below freezing as the rain moves in and saturates from the top down, and evaporative cooling takes place prior to that low level saturation (wet- bulb effect). While pavement temperatures will probably remain above freezing, icing can occur on elevated surfaces (bridges, overpasses, power lines, etc. The start time of the Winter Weather Advisory is 1 AM, but we will be monitoring conditions to see if we have to bump up the start time at all.

Cronce

SHORT TERM

Issued 220 PM CDT Wed Apr 1 2026

Tonight through Thursday night:

Warm advection will drive isentropic lift over a warm frontal boundary tonight as low pressure moves from the lee of the Colorado Rockies to the Nebraska/Kansas border. Surface conditions will start out fairly dry to begin with as northeast winds are currently advecting dry air into the region from a high pressure over Canada. But, saturation should be achieved after 10pm and rain should spread in from southwest to northeast. With the dewpoints below freezing, there will be the potential for air temperatures to wet bulb pretty efficiently to at or below freezing. Right now, the best potential for this appears to be for the northern half of our CWA. With the surface wet bulbing and a warm nose aloft owing to the warm advection, freezing rain is expected to begin after midnight and continue through the early morning hours, generally wrapping up after dawn as surface warm advection raises temperatures and freezing rain potential ends. Total ice accretions look to be between 0.1 and 0.2 inches, although most of this accretion may occur on elevated surfaces (overpasses and powerlines) and untreated surfaces, as pavement temperatures still remain in the upper 30s. Regardless, with the anticipated ice accumulation, travel impacts Thursday morning are expected. A Winter Weather Advisory has been issued for the two northern rows of counties in our CWA from 1AM to 9AM Thursday to account for these winter weather impacts.

Then, our attention turns to the severe weather threat Thursday. As the surface low moves from the Nebraska/Kansas border into central Iowa Thursday afternoon, morning rain will give way to a bit of a lull in precip as a surface warm front lifts north into southern WI. Temperatures in the 60s are expected. Then, as the surface low approaches the southwestern corner of the state during the mid afternoon, a potent shortwave will overlap with the warm sector and triple point of the low providing forcing for ascent, and clusters of thunderstorms are expected to form from southwestern WI south into IL.

We'll have a brief window of sunshine before storms move in, but it should be enough to realize 1000 to 1500 J/kg SBCAPE, amid effective shear of 45 knots. A supercellular mode should be favored given the effective shear, storm relative helicity values in the 0-3km layer >250 m2/s2, and boundary perpendicular shear vector orientation. 0-3km CAPE values from the HRRR and RRFS depict ~150 J/kg over our two southern rows of counties lending confidence in good low level stretching potential with sickle shaped hodographs in the low levels. A few tornadoes look possible with this setup and the low level instability would also support damaging winds. Mid level lapse rates are modest at around 6.5 C/km, but any supercells may enhance a hail threat as well. The Storm Prediction Center has placed the southern half of our CWA under an enhanced risk to highlight these threats, with a Slight Risk extending into central WI.

Storms are generally expected to move into our far west around 4pm and exit east over Lake Michigan around 10pm. Temperatures then quickly cool into the mid 30s to low 40s overnight as the surface low passes and cold advection occurs over the region.

CMiller

LONG TERM

Issued 211 PM CDT Wed Apr 1 2026

Friday through Wednesday:

A brief surface ridge will quickly shift newd from srn WI into the nrn Great Lakes Fri AM, while low pressure around 1003 mb over KS moves to sw IA by 00Z Sat. Wly winds will thus shift to ely for the afternoon with high temps only in the 40s near the lake. Elsewhere 50s are forecast, but there is some uncertainty whether stratus clouds will linger into Fri. Clouds will then increase for the later afternoon, along with 20-40 percent chances for light rain over south central WI as 850-700 mb warm, moist advection begins.

An increasing sly 40 kt low level jet stream and increasing PVA aloft from the approaching upper low over SD, will then bring widespread showers and scattered storms to srn WI Fri nt. The sfc low approaching from IA will become more broad and show signs of occlusion as the upper low moves into wrn MN by 12Z Sat. The low and occluded front will pass Sat AM but a warm sector may briefly reach into se WI. Continued or new shower and storm development is expected along the fronts but may occur to the east over Lake MI for the 12-18Z Sat time frame. Rain chances for Sat AM range from 20 percent over sw WI to 50 percent at the Lake MI shoreline. Much of the convection Fri nt- Sat AM will be elevated with perhaps a low potential for large hail.

The broad occluded low will then gradually deepen as it lifts newd into the nrn Great Lakes later on Sat, then to wrn Quebec by 12Z Sun. Brisk wnwly winds and cold advection will prevail Sat afternoon into Sun with high temps from 45-50F for Sunday. The cool conditions will continue through Tue as a couple shortwave troughs in nwly flow aloft reinforce the cool air mass. They will also bring 20 percent chances for light rain and snow Sun nt-Mon nt. Large high pressure will then shift across the nrn Great Lakes on Tue, moving to New England and the Mid Atlantic States on Wed. Sly winds and warm, moist advection will then boost temps for Wed but also bring 20 percent chances for rain.

Gehring

AVIATION

Issued 809 PM CDT Wed Apr 1 2026

The MVFR clouds of 1200 to 2000 ft along the lakeshore disappeared during the late afternoon as drier air advected into the low levels. The dry air will continue to push inland and allow ceilings to become VFR for a few hours this evening before rain spreads in from the southwest. There is still some uncertainty about whether or not any low clouds still exist just offshore.

Steady light rain with pockets of moderate will spread into south central WI between 10 pm and midnight, and into southeast and east central WI between midnight and 3 AM. confidence is fairly high that areas along and south of a line from Lone Rock to Madison to Milwaukee will remain all rain tonight. There is still concern for freezing rain north of that line due to temperatures already in the lower to mid 30s and there is low level dry air in place that will help lower the temps as the rain moves in. Timing and duration of the freezing rain are still uncertain, but amounts between 0.1 and 0.2 inch are possible.

Ceilings will fall with the rain overnight, likely dropping to IFR below 1000 ft. Visibility below 3SM is also likely with the rain. Increasing moisture over southern WI as the night goes on may allow for LIFR ceilings and vsbys below 2SM during the morning hours.

While winds remain out of the east over all of southern WI during the late morning and early afternoon hours, winds just above the surface will start increasing and become strong over 40 KT above 2000 ft AGL. A period of non- convective low level wind shear is expected, and will end as the surface winds turn around to the south with the arrival of the warm front.

Cronce

MARINE

Issued 208 PM CDT Wed Apr 1 2026

Breezy northeasterly winds continue this afternoon as high pressure remains near James Bay and a sharper pressure gradient remains over Lake Michigan. Winds are expected to become easterly tonight and become stronger as low pressure of 29.4 inches enters the Central Plains. These winds will then reach gale force Thursday morning and through the day as a warm front lifts north over the lake.

Gales over the northern third of the lake will continue through the day, while the middle third may see a lull form the mid afternoon into the evening. Then southerly gales are expected over the middle third of the lake. A Gale Warning with two segments has been issued, with staggered end times. Thunderstorms are also expected over the southern two thirds of Lake Michigan tomorrow afternoon and evening.

Beyond, winds become light and variable Friday late morning into Friday afternoon before gusty northeast winds return ahead of a low pressure on Saturday.

CMiller

MKX WATCHES/WARNINGS/ADVISORIES

WI...Winter Weather Advisory...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056- WIZ057-WIZ058-WIZ059-WIZ060...1 AM Thursday to 9 AM Thursday.

LM...Gale Warning...LMZ261-LMZ362-LMZ364-LMZ563...7 AM Thursday to 9 PM Thursday.

Gale Warning...LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673- LMZ675-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876...7 AM Thursday to 1 AM Friday.

Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 4 AM Friday.