textproduct: Milwaukee/Sullivan

KEY MESSAGES

- A Winter Weather Advisory has been issued north of the Interstate 94 corridor for snow accumulation of 1 to 3 inches and around a tenth of an inch of ice accumulation Saturday night into Sunday morning.

- Thunderstorms may occur Sunday morning into the afternoon. These thunderstorms may feature hail.

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

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

SHORT TERM

Issued 1145 PM CDT Fri Mar 13 2026

Tonight through Monday Night:

Quiet conditions tonight into Saturday as high pressure has moved in overhead. This will only persist for a short period before we start to see the signs of the next system beginning to push in. This event appears likely to feature multiple transition phases from Saturday through Monday.

Phase 1: A low pressure system will develop over southeast Wyoming later Saturday morning into Saturday afternoon. As it develops expect a tongue of moisture and WAA at 700-850mb to swing in to southwest WI to begin seeding the atmosphere with moisture. Saturation may not be fully expected Saturday afternoon given the dry lower levels but toward the late afternoon there may be enough saturation down to the surface to allow for some initial snow chances. However, saturation isn't truly expected until Saturday evening when a significant increase in 700-850 Fgen moves in. This will bring a significant boost to the snow, which at that time would be expected to be the predominant p-type with potential for heavier snow toward central WI. Then because we will be warm advecting, a warm nose in the temperature profile aloft will develop with gradually increasing surface temperatures. This will cause a transition from snow, to mixed precip/freezing rain, and then all rain across southern WI by around midnight. The warm nose mentioned may also bring significant midlevel dry air where this could significantly undercut precip chances in general, possibly clearing out precip for upwards of 2/3 of the CWA overnight Saturday into early Sunday morning. A Winter Weather Advisory has been issued to capture this first phase. Snow accumulation will range from 1 to 3 inches in the advisory area along with around a tenth of ice accumulation from freezing rain (up to quarter inch of ice possible in a worse case scenario where freezing rain sits over the same area for hours). Highest icing and snow amounts will be over central WI.

Phase 2: The low is then expected to approach from the west and pass along the southern border of Wisconsin through the day on Sunday. There may be a continued gap in our area from dry air where warmer temperatures begin nudging in significantly with breezy southerly winds and WAA where winter weather is minimalized across most of the CWA. There may very well be a very sharp temperature gradient over the northern portions of the CWA where snow/mixed precip remains a concern but is far more uncertain. The rest of the CWA would see some drizzle risk with the low but largely remaining dry (perhaps even seeing some clearing?). With CAMs and long term models bringing in warm temperatures, primarily along and south of I-94 at this time, MUCAPE is expected to increase to around 500 to 1000 J/kg across primarily south central and southeast WI. This will bring potential for some thunderstorms, especially as either the cold front or the triple point of the low moves through Sunday afternoon. Some of these thunderstorms may have small hail, few stones up to an inch possible but storms will be elevated. However, it is worth mentioning that the newest CAMs suggest some potential for storms even Sunday morning out ahead of the front as well. Still a lot of uncertainty in how this time period plays out.

Phase 3: Banded snow is then expected late Sunday afternoon into Monday as the deformation zone of the low moves in and cold air wraps into the area behind the front. There may be some freezing drizzle at the onset of this deformation band, but it should be transitory as snow pushes in directly behind it. The Sunday afternoon through Monday time period will feature the majority of the snow accumulation for southern Wisconsin with generally 5 to 9 inches expected, with the most in this range over central to east central Wisconsin. Along with the deformation zone, a very tight pressure gradient is expected to move over the region and winds will gust to 45 mph, leading to blowing snow and reduced visibility. Snow character is expected to be wet at the onset of the snow Sunday, but should change to a drier snow with time as cold air wraps into the area, especially Monday. For now, a Winter Storm Watch remains over the area from 4pm Sunday to 7pm Monday, given some remaining shifts in the snow band and some uncertainty regarding totals through that time period. Blizzard-like conditions will be possible with the backside of this system.

Kuroski

LONG TERM

Issued 1145 PM CDT Fri Mar 13 2026

Tuesday through Friday:

Looking further into the work week, there will be a few chances for additional precipitation. As the robust troughing from Sunday/Monday pulls east, the 500mb heights will slowly be rising. There will be a few shortwave troughs moving through the flow as a near stationary ridge remains parked over the western CONUS, which will bring us those precip chances. The first opportunity will be with a quick moving shortwave Tuesday night into Wednesday morning with a (40-55% chance). Ensembles seem to be handling this system well with the upper level and mid level troughing. The one thing to keep an eye on will be the winds and dewpoints. Until winds become southerly and we get some moisture advection the dewpoints depressions look to be pretty large, which may whittle away any incoming snow (virga likely until the low level moisten up). There is a signal that this will happen overtime. Snow will be the predominate precip type with temperature well below freezing.

The next potential for some precipitation is at the end of the extended for Friday. There is a lot of uncertainty with this next round which you can easily see in the deterministic guidance (GFS = shortwave, Euro = ridge, CAN = trough to east). This pattern continues when you look at the ensembles and is reflected well in the split among the cluster analysis. The EOF 1 and 2 show this well for days 6 and 7 with one having a monopole and the other a dipole distribution. All to say significant uncertainty in location, timing and strength in the 500 mb flow.

Beside this the only other item worth mentioning for the extended is the period of cold temperatures Monday night through Tuesday night. Monday night looks to be the coldest of the two nights with temperatures in the single digits, but Tuesday night brings temps in the teens. Thankfully this period of chilly temps seems short lived as temperatures should rise back to normal for Wednesday afternoon. near normal temps continue through the rest of the extended (highs in the 40s and overnight lows in the low 30s).

Patterson

AVIATION

Issued 1145 PM CDT Fri Mar 13 2026

VFR to MVFR conditions are expected through the period. VFR ceilings and visibilites will persist through Saturday afternoon. A scattered to broken mid level cloud deck that is overhead will be moving east southeast out of the area tonight with additional mid to high level clouds moving in from the west-northwest through Saturday. A few terminals may have a period of clear skies as these two cloud decks move through Wisconsin. The clouds will increase to a broken to overcast deck throughout the day Saturday. Heading into Saturday evening/night MVFR clouds around 1-3 kft will start to move in with incoming snow and mixed precipitation. Central and southwestern Wisconsin will have the best potential for those MVFR ceilings at the end of the period. Ceilings should continue to fall heading into Sunday night with MVFR to IFR conditions expected with both low ceilings and visibilities. These lower conditions should expand across southern Wisconsin Sunday.

Gusty northwest winds this evening are slowly diminishing. Winds will become light and variable early Saturday morning as a quick moving high pressure system passes through northern Wisconsin. East to southeast winds will set up behind the exiting high Saturday late morning. By Saturday afternoon east southeast winds will increase becoming breezy again. Winds will remain strong ahead of an incoming low pressure system through Saturday night. As the low pressure system tracks overhead there will be a quickly changing wind direction Sunday afternoon and brief lull in the gusts. Gusty northwest winds resume behind the low Sunday night.

Patterson

MARINE

Issued 1145 PM CDT Fri Mar 13 2026

Strong low pressure is pushing into southern Ontario tonight. Strong northwest winds continue this evening. Gusts have largely weakened below gale force as higher pressure nudges in from the west. Gales Warning will expire in the next hour.

East northeast winds will steadily increase Saturday night through Sunday, as a second low pressure system forms in the central Great Plains. The low will progress over far southern Lake Michigan Sunday night as it deepens, 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, across all of the open waters and nearshore waters late Saturday night through Monday night at various directions as the low progresses through the region. Gale Watches have been issued for much of Lake Michigan from Saturday night through Monday night. Where gale watches are not in effect is where a Storm Watch is in effect. The potential for storm force gusts is primarily for Sunday night and Monday for the northern two thirds of the lake. This is largely transitory but the potential for storm force gusts is fairly high at least at some point during this timeframe.

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 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 late Sunday night and linger into Tuesday behind the departing low, with areas of moderate to heavy freezing spray possible. Thus we have issued a Heavy Freezing Spray Watch as well.

Kuroski

MKX WATCHES/WARNINGS/ADVISORIES

WI...Winter Weather Advisory...WIZ046-WIZ047-WIZ051-WIZ052-WIZ056- WIZ057-WIZ058-WIZ059-WIZ060...7 PM Saturday to 10 AM 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.

LM...Gale Warning...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563- LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ777-LMZ779- LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 until 1 AM Saturday.

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.