textproduct: Milwaukee/Sullivan

KEY MESSAGES

- A Winter Weather Advisory north of I-94 corridor for 1-3 inches of snow and up to an tenth of an inch of ice accumulation tonight into Sunday morning. This advisory will then continue into the afternoon over central Wisconsin for continued light freezing rain potential.

- Thunderstorms capable of hail are possible Sunday late morning into the afternoon, mainly along and south of a Lone Rock to Mequon line.

- A Winter Storm Watch remains in effect from late Sunday afternoon through Monday. Snow accumulations between 5 to 9 inches and locally higher may occur along with a light glaze of ice. Wind gusts to 45 mph will cause blowing snow and visibility restrictions.

- Gale Warning, Storm Watch, and Heavy Freezing Spray Watch are now in effect for varying periods from Saturday night through Tuesday morning.

SHORT TERM

Issued 342 PM CDT Sat Mar 14 2026

Tonight through Monday:

Light echoes have been appearing on radar through the day as warm advection aloft touches off attempts at precipitation. The precipitation has been sporadically reported at the surface, though most of it has been evaporated by low level dry air. Some scattered light snow can't be ruled out as this band lifts northeast through the rest of the afternoon.

The precipitation mentioned above is in association with a baroclinic zone draped from the Dakotas into northern Illinois. As we head into tonight, low pressure will move into the high plains over Nebraska and increase 850-700mb WAA and frontogenesis over the upper Midwest. More substantial snow will then begin over the area, starting our expected prolonged winter weather event.

This afternoon, we are still confident in the storm unfolding in 3 phases, though the details of phase 2 and 3 still continue to shift this afternoon.

Phase 1: Confidence is high in the evolution of this phase and not much has changed since yesterday. Snow is expected to begin over east central Wisconsin after 7pm tonight and generally spread in coverage to as far south as a line from Milwaukee to Lone Rock. With time, warm advection aloft and at the surface will change this band of snow to mixed precipitation, and then rain over the area. Temperature profiles overnight will favor an overlap of snow and freezing rain mainly for counties north of the I-94 corridor. Little, if any wintry precip is expected from Milwaukee to Madison. The overlap of precip types will lead to 1 to 3 inches of snow accumulation and then ice accumulations up to a tenth of an inch tonight into Sunday morning. A Winter Weather Advisory remains in effect tonight into Sunday morning for counties north of I-94 for this phase.

Phase 2: The low is then still expected to approach from the west and pass along the southern border of Wisconsin Sunday afternoon into Sunday evening. As the low approaches, warm air at the surface will advect northward and generally stall just north of I-94 during the late morning and into the afternoon, creating a sharp frontal boundary and sharp temperature gradient. Temperatures in the 50s will exist south of the boundary and 30s north. Temperatures over central Wisconsin will still be around freezing, which will support a more prolonged period of freezing drizzle and freezing rain. With this more prolonged period of freezing precip potential, we have extended the Winter Weather Advisory for central Wisconsin into the afternoon to run up against the Winter Storm Watch, which starts at 4pm. Ozaukee and Washington Counties will still drop from the WW Advisory at 10AM, as they will likely transition to all rain with surface temperatures near 40, ending the freezing precipitation potential.

Thunderstorms are also possible, potentially starting as early as 8AM in southwestern WI, as MUCAPE of 500 to 1000 J/kg moves into the areas along with a prefrontal trough feature. A line of thunderstorms extending from Lone Rock south toward the WI/IL border is expected to then move from west to east over the area through 1PM. Models do generally show MUCAPE decreasing as storms move toward the lakeshore, but given mid level lapse rates around 7 C/km, some hail may occur. Following this first round, additional thunderstorms may occur as the cold front or triple point of the low move through later in the afternoon, but the CAPE profile is expected to be much skinnier and weaker, diminishing any potential for stronger storms.

Phase 3: Snow is still expected with phase 3 but the end time of impacts and snow amounts remain variable with the morning and afternoon model runs. Synoptically, as the surface low moves southeast of the area Sunday afternoon, cold air will wrap in behind the low pressure system and into the deformation zone of the low. This will support rain changing back over to freezing rain and mixed precip Sunday afternoon, and then over to all snow Sunday night. Wind is also expected to become very gusty, up to 45 mph as a sharp pressure gradient moves over the area.

From here models diverge, showing differences in snow totals overnight Sunday into Monday as well as differences in end timing. Some models like the HRRR and RRFS would end snow over the region as early as 6 to 9am, which would leave most of Monday windy, but dry. This would decrease potential winter impacts for Monday and lead to less of a need for local closures during the day. Models like the ECMWF and GFS however would linger snow into the early afternoon, which would change the flavor of local impacts.

Models have also trended lower with snow in recent runs. The Euro ensemble currently only features a 30 to 50% chance of snow greater than or equal to 6 inches over southwest Wisconsin. More alarming still, the GFS ensemble features only a 10 to 30% chance of snow greater than/equal to 6 inches in this area. HRRR and RRFS runs also corroborate this trend. With the deformation zone of the storm featuring the lion's share of the expected snowfall for this winter event, the decreasing probabilities 6+ inches of snow in the GFS and ECMWF ensembles and CAM trends for a good chunk of our CWA gives us pause. We have elected to maintain the Winter Storm Watch until these details get ironed out in further forecast model runs. We envision some part of our CWA getting upgraded to a Winter Storm Warning heading into tomorrow (more likely toward central WI where higher snow totals and high winds will overlap) while the rest may only need a Winter Weather Advisory. CMiller

LONG TERM

Issued 342 PM CDT Sat Mar 14 2026

Monday Night through Saturday:

High pressure will build in from the northwest Monday night and Tuesday behind the departing low pressure system. Additionally, a colder airmass will continue to move in through Monday night, with the coldest temps of the month likely. Lingering moderate winds will add an extra chill to the air, with wind chills dropping to -5 to -15 later Monday night into early Tuesday morning. Despite a fair amount of sunshine under the high Tuesday morning into at least early afternoon, high temps will remain well below normal, only topping out in the low to mid 20s.

Low level winds will become southerly later Tuesday into Tuesday night as high pressure departs ahead of an approaching shortwave. Models are showing a decent amount of warm air advection aloft along and ahead of the wave Tuesday night into early Wednesday. Moisture will increase as well ahead of this wave, with a round of snow likely per latest models. Latest guidance would suggest snow would arrive from the west late evening, winding down west to east early Wednesday morning. Models range from 1-2" to about 2-4" with totals. These potential amounts and timing could result in impacts to the Wednesday morning commute. Plenty of time left for the details of this system to change though, given it's still a few days out.

Milder temperatures are expected to gradually build in during the second half of the week in response to upper ridging nudging in from the southwest. Mainly dry weather is expected during this period.

DDV

AVIATION

Issued 342 PM CDT Sat Mar 14 2026

Southeast winds will become easterly overnight and then modestly breezing into tomorrow ahead of low pressure. Tomorrow late morning into the afternoon, winds will then become southerly to light and variable for a time as the low pressure approaches and passes overhead, before winds come around to north and northwesterly following the low. Strong wind gusts are then expected Sunday night.

With the increasing moisture over the region, ceilings will decrease to MVFR to IFR overnight over most of southern WI save for near the WI/IL border. Snow and mixed precip is expected with the low ceilings.

Tomorrow ceilings will decrease to IFR everywhere, and some thunderstorms may occur through the daytime hours. A changeover to freezing rain and then snow is expected across the area late Sunday afternoon into Sunday night.

Southerly LLWS to 50 knots is also possible Sunday morning ahead of the low pressure. This will be possible along and south of a line from KMSN to KMKE.

CMiller

MARINE

Issued 342 PM CDT Sat Mar 14 2026

High pressure of 30.2 inches will slide east later today and easterly winds will steadily increase tonight through Sunday, as a low pressure system around 29.3 inches forms in the central Great Plains. A Small Craft Advisory may be needed for a few hours this evening prior to the start of Gale Warning. The low will progress over far southern Lake Michigan Sunday evening as it deepens to around 29.1 inches, resulting in strong northerly winds developing.

Strong winds will shift out of the northwest Monday, as the strong low continues to move into Ontario. Expect another prolonged period of gales and storm force gusts early Sunday morning through Monday night as the low progresses through the region. The best chance for storm force gusts will be across the northern two-thirds of the lake.

Prolonged snow is expected Saturday night through Monday, some of which could be heavy over northern portions of the lake. Sleet or freezing rain should mix in with rain and snow over central and parts of northern Lake Michigan Saturday night into Sunday, with mainly rain and perhaps a few thunderstorms in the far southern portions of the lake Sunday into Sunday evening. Snow is then expected over southern portions of the lake Sunday night into Monday night.

Freezing spray potential will increase Monday and linger into Tuesday behind the departing low, with areas of moderate to heavy freezing spray possible. The Heavy Freezing Spray Watch continues.

DDV

MKX WATCHES/WARNINGS/ADVISORIES

WI...Winter Weather Advisory...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056- WIZ057-WIZ058...7 PM Saturday to 4 PM Sunday.

Winter Storm Watch...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056-WIZ057- WIZ058-WIZ059-WIZ060-WIZ062-WIZ063-WIZ064-WIZ065-WIZ066- WIZ067-WIZ068-WIZ069-WIZ070-WIZ071-WIZ072...4 PM Sunday to 7 PM Monday.

Winter Weather Advisory...WIZ059-WIZ060...7 PM Saturday to 10 AM Sunday.

LM...Gale Watch...LMZ080-LMZ673-LMZ675-LMZ777-LMZ779-LMZ874-LMZ876- LMZ878...1 AM Sunday to 7 AM Tuesday.

Heavy Freezing Spray Watch...LMZ080-LMZ261-LMZ362-LMZ364- LMZ366-LMZ563-LMZ565-LMZ567-LMZ643-LMZ644-LMZ645-LMZ646- LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779-LMZ868-LMZ870- LMZ872-LMZ874-LMZ876-LMZ878...4 AM Monday to 1 PM Tuesday.

Gale Watch...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567- LMZ669-LMZ671-LMZ868-LMZ870-LMZ872...1 AM Sunday to 7 PM Sunday.

Storm Watch...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567- LMZ669-LMZ671-LMZ868-LMZ870-LMZ872...7 PM Sunday to 1 AM Tuesday.

Gale Watch...LMZ643-LMZ644-LMZ645-LMZ646...4 AM Sunday to 1 AM Tuesday.