textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Frost and patchy fog will burn off within the next few hours.

- Additional frost expected tonight and Friday night, with freezing temperatures possible away from Lake Michigan.

- Pop-up showers continue during the afternoon hours today and Friday. Some graupel could mix in with the rain.

- Additional shower & thunderstorm chances Sunday night through the middle of next week.

UPDATE

Issued 652 AM CDT Thu Apr 30 2026

Patchy fog is becoming locally dense in low lying areas this morning, but will burn off within the next hour or two as temperatures rise. A Fog Advisory has been issued to account for this threat for Washington, Jefferson, Waukesha, Racine, Kenosha, and Walworth Counties. Widespread frost has been observed across inland areas away from far southern Wisconsin where cloud cover has lingered overnight, but will also burn off within the next few hours. A wave of showers will progress eastward through the day as a shortwave moves through once again, with showers becoming more numerous during the afternoon hours. An isolated graupel pellet is still possible.

MH

SHORT TERM

Issued 1145 PM CDT Wed Apr 29 2026

Rest of Tonight through Saturday Night:

Synopsis/Mesoanalysis: A broad upper trough will remain entrenched across the western Great Lakes through the first half of this weekend. Embedded small-scale perturbations will progress through the broad area of troughing, combining with daytime heating to support additional periods of pop-up rain showers across southern Wisconsin both Thursday and Friday afternoon. Hazards aren't expected in any additional shower development, though a few graupel pellets could mix in with the rain drops. Conditions will dry out on Saturday as shortwave ridging moves in from the Northern Plains. Broad high pressure over the Canadian Great Plains will maintain north-northwest breezes across the region through Friday night, resulting in continued below normal temperatures. Anticipate areas of frost development during the overnight periods tonight, and once again on Thursday night and Friday night. Frost Advisories remain in effect for parts of southern Wisconsin tonight, with additional headlines anticipated through the end of the week. Be sure to bring any cold-sensitive plants indoors during overnight periods.

Rest of Tonight: Any last showers will push out of east-central Wisconsin after midnight, giving way to at least partly clear skies across southern Wisconsin. Clearing skies will combine with light surface winds to cool overnight lows. Temperatures in the low-mid 30s will combine with the aforementioned light surface winds to support areas of frost, with the most widespread potential generally expected to the north of I-94 and west of I-41. Expected coverage of more widespread frost potential has increased in the evening forecast update, with Fond du Lac, Dodge, Washington, Jefferson, Dane and Waukesha Counties being added to the pre-existing Frost Advisory between 12 AM and 8 AM. Be sure to move any cold-sensitive plants inside in any of these locations. Ongoing in current obs, brief pockets of shallow fog could precede frost development, with the expectation for a relatively quick transition to frost as a very shallow near-surface moist layer deposits out.

Thursday: Fair-weather cumulus clouds will quickly blossom from late morning into the afternoon as the surface heats beneath an overall cold column overhead. With time, expect that said cumulus will grow deep enough to support hit & miss shower development across the area. Not anticipating any hazards in this activity, though an overlap of very weak MUCAPE & very cold temperatures aloft could support some graupel pellets in any deeper updrafts. No impacts are anticipated.

Thursday night: Expecting colder overnight lows relative to tonight, with another round of frost development forecast over southern Wisconsin. Anticipating that widespread frost coverage will be higher compared to tonight, with a larger part of the area likely needing a Frost Advisory. Will be addressing the need for Thursday night frost/freeze headlines in the Thursday afternoon forecast update.

Friday: Another round of diurnal rain showers is forecast, though coverage might be a touch lower compared to Thursday. Some graupel pellets could mix in with rain once more given still very cold temperatures overhead.

Friday night: Anticipating another round of widespread frost development, with additional frost headlines likely. Details regarding the precise timing & placement of headlines will be refined in coming forecasts.

Quigley

LONG TERM

Issued 1145 PM CDT Wed Apr 29 2026

Sunday through Wednesday:

Synopsis: Shortwave ridging will be short-lived/confined to the day on Sunday, with a renewed area of mean troughing becoming established from the Hudson Bay to the western Great Lakes through most of the long term period. Positioning of the trough will place southern Wisconsin in line for additional shortwave & surface frontal passages Sunday night through the middle of next week, with each shortwave/surface front passage bringing chances for additional showers and thunderstorms. Near or slightly below normal temperatures & only modest moisture returns are expected to keep thunderstorms below severe levels, though trends will continue to be monitored over coming forecasts.

Sunday through Monday: Currently anticipating a pair of shower & thunderstorm chances across southern Wisconsin as two shortwaves & surface fronts move through the western Great Lakes. Currently favored periods are Sunday afternoon/evening and Monday evening/night, with precise trends being refined in coming forecasts. MUCAPE will be sufficient for a few thunderstorms in each batch of activity, with current progs from the LREF implying low enough values to keep activity sub-severe. Will nevertheless be monitoring trends over coming updates.

Tuesday into Wednesday: Additional showers & storms are forecast as another upper wave and surface front move through the region. Have largely maintained precip forecasts from that of the NBM, which depicts broad 20-40% probabilities over most of this time frame. Maintained these probabilities not because it will be raining for the entirety of the Tuesday-Wednesday time frame, but rather that high spread remains amongst global guidance regarding the precise timing of the upper wave and frontal passage. Anticipate that the range of mentionable precip probs will decrease as timing/placement trends clarify through this weekend.

Quigley

AVIATION

Issued 652 AM CDT Thu Apr 30 2026

Patchy fog with localized areas of dense fog in low lying areas has developed across portions of southeastern Wisconsin, with locally dense low- lying fog. Fog will burn off within the next couple hours. Expecting isolated showers to progress through the region this morning, becoming scattered to widespread this afternoon. Expecting VFR conditions to continue within these showers. Showers will taper off west to east overnight. A few MVFR ceilings could work their way into southeastern Wisconsin off Lake Michigan late tonight, but otherwise expect VFR conditions to continue.

Generally northwesterly winds throughout today, shifting to become northerly tonight, then becoming light and variable late tonight into Friday morning.

MH

MARINE

Issued 1145 PM CDT Wed Apr 29 2026

Widespread gales are not expected through the duration of the period across the open waters of Lake Michigan. Currently north-northwest winds will continue through the end of the week as 1002 mb low pressure shifts into the Canadian Maritime Provinces & 1022 mb high pressure builds into the northern Great Plains. Winds will trend south-southwesterly Saturday into Sunday as the aforementioned area of high pressure moves into the Ohio River Valley and 1000 mb low pressure forms over the Hudson Bay. Winds will briefly veer westerly Sunday night into Monday as a weak cold front crosses Lake Michigan. Showers and a few thunderstorms will accompany the front, with severe weather not anticipated at this time.

A second area of stronger low pressure near 992 mb will develop over the Lake Superior vicinity during the day Monday, ultimately shifting toward the southern Hudson Bay and Quebec on Tuesday. Progression of the low will allow winds to trend west-southwesterly Monday night through Wednesday. A cold front is forecast to cross the open waters Wednesday afternoon, bringing a northwest wind shift. Additional periods of showers and embedded storms are forecast Sunday night into the middle of next week, with widespread severe thunderstorms not expected at this time.

Widespread Small Craft Advisory conditions are not expected through the duration of the period in nearshore zones. West-northwest winds will continue tonight through the end of the week as high pressure builds in from the northern Great Plains. Winds will trend west- southwesterly this weekend as low pressure develops near the Hudson Bay. Winds will trend westerly Sunday night into Monday morning as a weak surface front crosses Lake Michigan. West-southwest winds return Monday afternoon into Wednesday as a second surface front approaches Lake Michigan from the west. Periods of showers & embedded thunderstorms are forecast Sunday night into Monday, Monday evening, as well as Tuesday into Wednesday. Severe weather is not anticipated at this time, though trends will continue to be monitored.

Quigley

MKX WATCHES/WARNINGS/ADVISORIES

WI...Frost Advisory...WIZ046-WIZ047-WIZ051-WIZ056-WIZ057-WIZ058- WIZ059-WIZ063-WIZ064-WIZ065 until 8 AM Thursday.

Dense Fog Advisory...WIZ059-WIZ064-WIZ065-WIZ070-WIZ071-WIZ072 until 9 AM Thursday.

LM...None.