textproduct: Milwaukee/Sullivan

KEY MESSAGES

- Patchy fog across southern Wisconsin will slowly diminish after sunrise.

- Warm temperatures are expected today across most of the area, as gusty southwest winds develop. Highs may rise into the lower to middle 70s over most of the area.

- Some chances (around 20 to 30 percent) for light rain to occur later Saturday night into Sunday morning, as a cold front shifts southward through and south of the area. Cooler temperatures and gusty winds are expected.

- Chances (mainly 20 to 30 percent) for precipitation returns to the area for middle to later portions of next week.

UPDATE

Issued 637 AM CDT Sat Mar 21 2026

Patchy fog across southern Wisconsin will slowly start to burn off after sunrise this morning. Over the next 30 minutes or so as temps and winds are at there lowest, the fog will be at its worst. Overall visibilities are around 4 SM or better so nothing super noteworthy for a Saturday morning.

As the low pressure system in North Dakota moves east this morning, a warm front will move across the state. This will be a dry frontal boundary, but will mark the shift to southwest winds and start of WAA. There remains small uncertainties in how warm it will be across southern Wisconsin based on the timing of the frontal passage. TLDR faster the front moves through the warmer it becomes and vice versa. Winds should be strong enough to keep the cooler air from Lake Michigan right along the shore line to just off shore. So there will be a tight temp gradient along the lakeshore counties. Not major changes to the forecast.

Patterson

SHORT TERM

Issued 1226 AM CDT Sat Mar 21 2026

Overnight through Tuesday:

Patchy fog should linger overnight into early Saturday morning, as a sharp inversion develops over these areas with a solid snowpack on the ground. Some dense fog may occur, mainly in low lying areas. The middle to high clouds that are moving through may deter some of the fog development. These clouds should move out of the area by later Saturday morning.

Warm air advection continues into Saturday, as winds shift from the southeast and south to southwest. Gusty southwest winds should develop by midday and should push to most of the lakeshore areas by middle afternoon. Areas toward Port Washington and Sheboygan may remain onshore until the southwest winds arrive by 00Z Sunday. This should allow for warm highs into the lower 70s to reach most of the lakeshore areas, with lower to middle 70s inland.

A cold front will push south through the area Saturday evening, with north to northeast winds increasing overnight into Sunday. Cold air advection will bring cooler temperatures into the area. A low cloud deck should push southward into the area during this time as well. There remains some low to mid level frontogenesis response that shifts southward through the area during this time.

Forecast soundings remain mixed with the amount of deep moisture available, so there is uncertainty with how much precipitation may occur. For now, kept the 20 to 30 percent chances for light rain later Saturday night into Sunday morning. A little light snow may mix in on the back end of the precipitation Sunday morning, though this potential is rather small (under 20 percent).

High pressure will then move across the region Sunday night and Monday, then to the east Monday night. South to southwest winds Tuesday may usher milder temperatures back into the area with some warm air advection.

Wood

LONG TERM

Issued 1226 AM CDT Sat Mar 21 2026

Tuesday night through Friday night:

Synopsis: Modestly cooler conditions will prevail Wednesday afternoon behind a late Tuesday/Tuesday night frontal passage. Significantly colder conditions continue to appear unlikely, with winds shifting out of the southeast by the afternoon hours. Loose consensus amongst the global ensemble suite suggests that broad low pressure will develop in the Central Plains Wednesday afternoon and night, with surface pressure falls elongating across the eastern half of the CONUS through Thursday night.

Said surface evolution thus continues to put a cold front on track to move through the western Great Lakes during the day Thursday. Precip chances return to the forecast Wednesday night into Thursday along and ahead of the front. Global guidance suggests that seasonably strong high pressure will settle into the western Great Lakes Thursday night through Friday night behind the departed front, resulting in a more noticeable cool down at the end of next week.

Wednesday Night into Thursday: Precip chances return to the forecast along and ahead of a passing cold front. Could see precipitation focus along pre-frontal warm advection Wednesday evening/night, with chances continuing into the day Thursday as the passing surface boundary. Current temperature forecasts and probabilistic p-type forecasts continue to point toward all rain, with trends continuing to be monitored in coming updates.

Initial forecasts from the LREF suggest that instability for convection will remain largely south of the region, which is the likely outcome if the surface progression currently projected by the ECMWF and Canadian ensemble systems verifies. It is worth noting, however, that the GEFS presents a deeper and more northeast progression of surface low pressure, which would open the door for a slower frontal passage and more time for instability to build into southern Wisconsin. Will be treating this solution as an outlier for the time being and leaving any thunder mentions out of the forecast, but will be watching for any changes over coming updates.

Quigley

AVIATION

Issued 637 AM CDT Sat Mar 21 2026

Patchy fog this morning will bring VFR to MVFR conditions, which should improve shortly after sunrise. MVFR visibilities of 4 to 5 SM will be few and far between.

Light and variable winds this morning will pick up and become due southerly for a few hours ahead of an approaching warm front. As this front passes winds will shift to southwesterly and become breezy. This front is expected to pass late this morning into early this afternoon. Dry and breezy conditions remain through this evening.

A cold front will pass tonight into Sunday morning bringing MVFR to IFR conditions. Ceilings will drop to around 1-3 kft ahead of the cold front and will move from north to south. There is a small chance (10 to 25%) for some light rain with this cold front. The better chances will be across eastern Wisconsin. The chances for rain diminishes as you head west. Winds will shift to the north to northeast behind this cold front at the end of the period. Rain may linger into the late morning.

Patterson

MARINE

Issued 1226 AM CDT Sat Mar 21 2026

Winds will become light overnight, as high pressure around 30.3 inches builds in from Ontario. The high will move east into Saturday, allowing winds to shift southeast to south. Low pressure around 29.5 inches developing in eastern Wyoming Saturday morning will move east southeast Saturday night to the south of Lake Michigan. This will allow southwest winds to shift to the north and northeast and become gusty later Saturday night into Sunday morning.

Gusty southwest winds this afternoon and early evening may reach Small Craft Advisory levels for the nearshore waters.

The low should move across central Illinois into Indiana Sunday, as it deepens to around 29.4 inches. A few northerly gales are possible Sunday, mainly over southern portions of the lake. Gusty north to northeast winds and building waves will likely reach Small Craft Advisory levels Sunday into Monday morning.

High pressure around 30.4 inches should then bring decreasing winds for Monday.

Wood

MKX WATCHES/WARNINGS/ADVISORIES

WI...None. LM...None.