textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Rain and embedded thunderstorms are expected to develop Tuesday evening, with the first round of rain producing isolated strong to severe storms with the primary threats being hail 0.5 to 1 inch in diameter and frequent lightning.

- Rain will transition to a brief period of freezing rain and snow late Tuesday night as low pressure exits. Up to a glaze of icing and up to an inch of snow possible in central Wisconsin, with southern Wisconsin (I-94 southward) seeing less than an inch of snow.

- Increased precipitation chances (70-80%) Thursday evening/night, with expectations for some snow to mix in with rain overnight into Friday morning.

- Additional precipitation chances develop Saturday into Sunday. High confidence in precipitation, but confidence in precipitation type and placement is lower. Snow is possible Sunday.

UPDATE

Issued 730 PM CDT Mon Mar 9 2026

No major changes to the going forecast, will be assessing both the hail / lightning threat (late Tue Afternoon into Tue evening) and wintry precip threat (Wed predawn thru Wed afternoon) when the 00z guidance rolls in. 18z guidance shows no substantial deviation from the existing forecast.

Sheppard

SHORT TERM

Issued 220 PM CDT Mon Mar 9 2026

This afternoon through Wednesday:

The forecasted weak front is slowly working its way eastward through southwestern Wisconsin this afternoon, with wind gusts finally diminishing across south-central Wisconsin. Temperatures continue to climb, with current temperatures ranging from 60 degrees in Sheboygan to 69 degrees in low lying and downsloping areas. Will likely see records broken this afternoon as we still have a few more hours of rising temperatures. In addition, expecting relative humidities to continue to fall, with minimums in the low 30s.

Tonight, winds will briefly become light and variable before turning northeasterly as a back-door cold front progresses southwestward through the region. This will bring in cooler air and temperatures in the mid 30s to low 40s.

Tuesday, expecting northeasterly winds to continue as low pressure develops in the central Plains and lifts northeastward into northern Illinois. Warm frontogenesis will create the first waves of precipitation across southern Wisconsin Tuesday afternoon into Tuesday evening. Very strong WAA aloft (850-700 mb) will contribute to a strong warm nose in the mid-levels and therefore MUCAPE in the 1000-2000 J/kg range. The first waves of storms to develop along the nose of this MUCAPE boundary in the mid-levels look to become capable of producing hail up to 1 inch in diameter (bulk shear in the 60 to 80 kt range and freezing levels around 700 mb while storm top nears 250 mb based on sounding data). Expecting storms to quickly devolve into multicellular clusters due to shear largely parallel to the frontal boundary, therefore then preventing storms from remaining severe through the overnight hours. However, an isolated stronger storm cannot be ruled out.

Cold air advection at the surface takes hold going into the late overnight hours Tuesday (after midnight), as low pressure ejects into Lower Michigan. The 850 mb warm nose is strong enough to linger through Wednesday morning, allowing for a period of freezing rain in regions that surface temperatures fall below freezing, then a transition to snow as the warm nose whittles away into the morning hours. Currently, temperatures are forecast to fall below freezing mainly north of I-94, but a slight shift in low track may allow for freezing temperatures through the I-94 corridor as well and therefore lead to impacts through the Madison and Milwaukee metros during the morning commute. Gusty northwesterly winds are also expected during this time. Temperatures are expected to rise slightly during the day to above freezing, which would allow for a transition to a mix of snow and rain through at least midday. A minor shortwave wrapping around the mean flow may contribute to snow/rain showers into the afternoon hours before tapering off.

MH

LONG TERM

Issued 220 PM CDT Mon Mar 9 2026

Wednesday night through Monday:

Low pressure exits eastward into southern Quebec Wednesday night, continuing to deepen as it ejects, leading to continued steady northwesterly winds throughout Wednesday night. Expecting lows in the mid-20s as high pressure builds into Thursday morning.

Winds shift southwesterly into Thursday afternoon ahead of an approaching low pressure system from the northern Plains. Temperatures will rise back into the mid-40s Thursday afternoon within the warm sector of this low, allowing for precipitation along the warm front in the afternoon hours to start as rain. Modeling currently indicates southern Wisconsin will remain in the warm sector through the late overnight hours, transitioning to a mix of rain and snow behind a cold front during the early morning hours Friday. Expecting this mix to produce minimal accumulations at this time. Modeling has been trending southward with the parent low, and a slight shift farther south could result in an inch or two in central Wisconsin.

Low pressure sweeps eastward out of the Upper Midwest by Friday afternoon, with high sun angle allowing for temperatures to recover into the low 40s even with gusty northwest winds. Winds will diminish into the evening under a ridge of surface high pressure, with overnight lows in the mid 20s again.

Saturday, low pressure will deepen in the lee of the Wyoming Rockies as a shortwave rides southeastward through the northern High Plains. This low will allow for warm frontogenesis to develop across southern Wisconsin, bringing chances for precipitation (20-40%). Precipitation will likely start as snow during the early morning hours, but transition to rain into midday Saturday as the warm front lifts northward. Saturday night into Sunday morning, low pressure deepens and ejects northeastward into northern Illinois. This will serve to enhance CAA across Wisconsin, and may bring a return to snow across central to southern Wisconsin through the late overnight hours into Sunday morning. Precipitation chances are high (~80%) at this time. Current modeling indicates low pressure progressing right through southern Wisconsin, which may bring more of a drizzle/warm sector scenario to the area before the cold front brings back snow during the afternoon to evening hours. Ensemble guidance is indicating a moderate (50-70% chance) for totals around 3 inches, so keep an eye on the forecast as the event nears. Gusty northwest winds will also develop Sunday afternoon after the low passes eastward.

Snow tapers off into Monday morning as low pressure ejects eastward into the Northeast U.S., with a brief wave of Arctic high pressure bringing highs in the mid-20s. High pressure lingers through Monday night.

MH

AVIATION

Issued 730 PM CDT Mon Mar 9 2026

Clear skies with light and variable winds through this evening. A backdoor cold front is expected to slide southward down the Lake Michigan shoreline (and southern WI as a whole, albeit weaker inland) overnight tonight, shifting winds northeast. Said northeast winds gain speed into Tuesday morning, roughly 10 to 15 knot sustained winds with 20 to 25 knot gusts (mainly by the shoreline). Fuel Alt MVFR cloud ceilings (in the ballpark of 1,000 to 2,000 ft AGL) are expected to gradually arrive behind the front, with rough timing reflected in the TAFs (used SCT to indicate the earlier possible arrivals, and BKN for the expected ceiling arrivals), generally reaches the shoreline first then spreads inland through the course of Tuesday. Some marine fog may briefly roll into shoreline TAF sites late tonight / Tuesday as well, confidence is low.

The northeasterly breeze continues Tuesday afternoon and evening as a low pressure system drags a warm front into Illinois. Scattered to numerous thunderstorms are expected to fire up along and north of the warm front late Tuesday afternoon through Tuesday evening, and some of these showers / storms should drift north into southern WI (70-95% rain chances, highest further south and east). There is a conditional threat for frequent lightning and large hail.

Sheppard

MARINE

Issued 220 PM CDT Mon Mar 9 2026

Breezy southwest winds will diminish through this evening as high pressure around 29.9 inches pushes into the Upper Great Lakes. Marine dense fog may develop over far southern Lake Michigan early Tuesday morning with the lull in the winds. A cold front will gradually bring a wind shift to the west- northwest and eventually north- northeast. This front will accelerate from north to south overnight down Lake Michigan overnight. Brisk northeast winds of 15 to 25 KT developing Tuesday morning will persist through Tuesday night.

Low pressure around 29.6 inches then develops in the central Great Plains and progresses into northern Illinois Tuesday night. There is some potential for isolated thunderstorms across the southern third of the Lake. Low pressure ejects to the lower Great Lakes into Wednesday morning, turning winds northwesterly. North to northwest gales are possible Wednesday morning through Wednesday afternoon, mainly over the south half of the lake. Winds gradually diminish into Thursday morning.

Another round of gales is possible Thursday night into Friday as a compact clipper low of 29.2 inches crosses northern Lake Michigan.

Cronce

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643-LMZ644...3 AM Tuesday to 7 PM Wednesday.

Small Craft Advisory...LMZ645-LMZ646...10 AM Tuesday to 7 PM Wednesday.