textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Rain showers ending late this evening, with a few sprinkles or flurries possible through the predawn hours.

- Rain chances (~30-50%) return Sunday evening.

- Increasing potential for pop-up snow showers Monday afternoon & evening, with some PM commute impacts possible.

- Active pattern continues Tuesday night into next weekend, with multiple additional chances for mainly rain and a few thunderstorms. Some wet snow is possible Tuesday night.

SHORT TERM

Issued 1220 AM CDT Sun Apr 5 2026

Today through Monday Night:

Synopsis/Mesoanalysis: GOES water vapor imagery depicts several prominent features influencing both ongoing and short term weather conditions late this evening. An upper low continues to progress east toward Ontario, with residual lift on the back side of the low supporting isolated sprinkle or flurry potential moving into the predawn hours. Further upstream, a pair of shortwaves are apparent over Lake Winnipeg & the Northwest Territories. The two shortwaves will progress southeast during the period, with the leading perturbation moving across Wisconsin from late Sunday afternoon into early Monday morning. Lift from the wave, in addition to forcing from a surface cold front moving across southern Wisconsin, will support returning rain chances Sunday evening through the predawn hours Monday. Conditions will dry out after sunrise Monday, with precip-free weather lasting into the first part of the afternoon hours. Precip chances return late Monday afternoon into Monday evening as the wave currently over the Northwest Territories settles over Lake Huron. Late afternoon/early evening timing, along with very cold temperatures aloft, will support greater snow potential in the Monday afternoon/evening round of precipitation. If wintry precipitation does materialize, Monday evening commute impacts will be possible.

Rest of Tonight: Widespread precipitation potential has ended, though a few light sprinkles or flurries remain possible through the predawn hours as an upper low departs the region. Best potential will be along & north of I-94, where proximity to the vacating low & its residual forcing will be greatest. Whether any drops or flakes reach the surface remains uncertain, as steady drying will be ongoing in the lower portions of the column. Have accounted for the isolated potential with 10-15% precip probabilities through 5 AM, and will make adjustments as radar/obs trends call for through the overnight. Not expecting any measurable accumulation or impacts in any flurries/sprinkles that occur late tonight.

Sunday Night: Rain chances return ahead of an encroaching shortwave and surface front. Projected surface temperatures and forecast soundings suggest that thermal profiles will be mild enough for all rain, so have continued an all rain forecast in the evening update. Will nevertheless need to monitor trends in east-central Wisconsin, where some wet snowflakes could mix in if conditions trend cooler than current guidance suggests. Not expecting meaningful accumulations or impacts in the event that some wet snowflakes mix in with rain over east-central Wisconsin.

Monday Afternoon/Evening: Potential is increasing for pop-up snow showers as a second upper wave moves over the Lake Huron vicinity. Current expect the best snow shower potential to reside over east- central Wisconsin, where proximity to the encroaching wave will be greatest. Anticipate a strong diurnal contribution to activity given very cold temperatures aloft & breaks in the cloud cover through the early afternoon time frame. Forecast soundings depict deep mixing from the surface to/through the 700 mb level, with some modeled profiles hinting at some small CAPE in the event that sufficient surface heating is realized. Will thus need to watch for a more convective character in snow showers, which would act to boost snowfall rates. Hit & miss nature of the snow showers, in addition to potentially enhanced rates within them, could thus lead to rapid changes in visibility over short distances Monday afternoon & evening. Will thus be watching closely for possible commute impacts over coming updates.

Quigley

LONG TERM

Issued 1220 AM CDT Sun Apr 5 2026

Tuesday through Sunday:

Tuesday night through Wednesday: The next disturbance arrives over the western Great Lakes, bringing the next chances for precipitation to southern Wisconsin. Precip will begin Tuesday night as a wing of broad warm advection & affiliated frontogenesis spreads north across the region, with precipitation chances continuing into the day Wednesday as a surface cold front approaches & crosses southern Wisconsin. Overnight timing of the initial WAA/FGEN precipitation, in addition to cold antecedent temperatures, may support snow or rain/snow mix through Tuesday night, with the column becoming mild enough for all rain by Wednesday morning. Will thus need to monitor trends for some potential snow accumulation Tuesday night into early Wednesday morning. While most appreciable probabilities for 1"+ of accumulation remain over north-central and northeast Wisconsin, 40%+ probabilities of at least trace accumulations sag into our northern two tiers of counties. Will continue to monitor trends. LREF guidance hints at some weak (< 100 J/kg) MUCAPE building into the area ahead of the Wednesday PM cold front, so a few rumbles of thunder could mix in with rain on Wednesday. Currently expecting severe weather potential to remain over the central Great Plains, where instability is progged to be much higher.

Thursday through Sunday: Broadly divergent upper level winds & embedded mid-level waves will support continued periods of on again off again precipitation. Initial temperature forecasts appear mild enough for all rain. Could see a few thunderstorms mixing in with rain if sufficient CAPE can build into the western Great Lakes, though far greater storm potential will remain concentrated in the Great Plains where instability will be maximized.

Quigley

AVIATION

Issued 1220 AM CDT Sun Apr 5 2026

Mainly VFR flight categories prevail late this evening across southern Wisconsin. Expect CIGs to gradually lower through the second half of the overnight, with MVFR flight categories returning to all aerodromes by daybreak. Can't rule out a few more sprinkles or flurries through the predawn hours, though confidence in coverage & impacts in the vicinity of terminals remains too low to justify any mentions in the 06Z update. Will be monitoring radar trends through the overnight & make any amendments if necessary. Low stratus clouds will shift east of the region by early Sunday afternoon, allowing VFR flight flight categories to return areawide. Clouds will increase once more Sunday evening ahead of the next disturbance. Said disturbance will bring scattered rain to southern Wisconsin. Have accounted for this potential with PROB30 groups at all fields in the 06Z update. Will address the need for TEMPO and/or prevailing groups in coming forecasts.

Quigley

MARINE

Issued 1220 AM CDT Sun Apr 5 2026

1002 mb low pressure is moving toward the Ontario-Quebec border this evening, resulting in continued gusty northwest winds across the open waters of Lake Michigan. Said gusty winds will continue into Sunday morning as the low deepens to near 988 mb over Quebec. The potential for a few gale force gusts will continue through Sunday morning across the northern third of Lake Michigan. Continue to anticipate that that headlines won't be necessary given the isolated nature of any such higher gusts. Winds will taper Sunday afternoon & night as 1030 mb high pressure builds into the Great Plains. Scattered rain and snow showers ongoing through this evening will taper through the second half of the overnight hours tonight. Additional rain and snow showers are forecast Sunday night into Monday.

Northwest winds will increase once more during the day Monday as a small area of 1016 mb low pressure develops over Lake Huron. Similar to ongoing conditions, a few gale force gusts are possible over the northern half of the open waters during the afternoon hours, but are expected to be isolated and brief enough to preclude the need for any headlines. Trends will continue to be monitored. Winds will decrease Monday night into Tuesday as 1032 mb high pressure moves over and east of the open waters. Areas of moderate freezing spray are possible over the northern half of the lake Monday afternoon and evening.

1002 mb low pressure will form over the northern Great Plains & approach Lake Michigan Tuesday night into Wednesday, resulting in increasing southerly winds across the waters. Winds will remain gusty into Wednesday night as the low passes near or just north of northern Lake Michigan. Will be monitoring for more widespread gale potential during this time frame, with the need for headlines being evaluated as this portion of the period draws closer. Winds will taper during the day Thursday, when 1030 mb high pressure is forecast to move from the northern Great Plains toward Lake Superior. Showers and a few thunderstorms are expected Wednesday into Thursday, with severe weather potential appearing low at this time.

Small Craft Advisory conditions continue in nearshore zones through Sunday afternoon, with additional advisory conditions anticipated during the day on Monday. Will handle Monday's conditions with a new headline once the ongoing Small Craft Advisory expires. Winds and waves will taper Monday night into Tuesday. Wind gusts will increase once more Tuesday night through Thursday as low pressure approaches from the northern Great Plains. Expect that at least Small Craft Advisories will be necessary during this time frame, with gale potential being monitored over coming forecasts.

Quigley

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...Small Craft Advisory...LMZ643-LMZ644-LMZ645-LMZ646 until 1 PM Sunday.