textproduct: Green Bay

KEY MESSAGES

- Snowmelt will cause increased flows and rising levels on rivers and streams. Several rivers may reach bankfull or even minor flood stage within the next couple days.

- Rain, mixed with sleet at times, is expected late tonight into Sunday morning. Locally slippery road conditions are possible, especially in northern WI. - Temperatures will cool to near normal tonight into Sunday, then rise to above normal again during the middle of the work week.

- A wintry mix of precipitation is possible during the middle of next week, with best chances occurring regionwide Wednesday night into Thursday.

DISCUSSION

Issued at 232 PM CDT Sat Mar 21 2026

After a slow start due to extensive cloud cover, temperatures climbed into the middle 50s to lower 60s across the southwest part of the forecast area early this afternoon. Farther northeast, lingering clouds and southeast winds off the cold waters of Lake Michigan were holding temperatures in the upper 30s and 40s. Daytime mixing was producing breezy conditions, with south winds gusting to 20 to 30 mph.

A clipper low pressure system will move through the region this evening, causing a cold front to sweep through the forecast area. Models show strong mid-level FGEN forcing with this system, which should bring a band of post-frontal precipitation through the area late tonight into early Sunday. Precipitation type is a bit tricky, with a fairly strong, but eroding warm layer aloft that gets undercut by post-frontal CAA, and boundary layer temperatures that are initially supportive of rain, but cool substantially overnight/early Sunday. Feel that the most likely p-types will be rain and sleet, but can't rule out spotty light freezing rain and snow. Regardless, don't envision any significant snow or ice accumulations, with locally slippery road conditions expected as temperatures drop below freezing in northern WI. The precipitation is expected to taper off in our southeast counties by mid to late morning, with overcast conditions becoming SCT-BKN in the afternoon. High temperatures drop back to normal or a little below, with highs only in the 30s to middle 40s.

High pressure will then provide mainly dry weather and seasonable temperatures Sunday night and Monday. Small precipitation chances occur across mainly northern WI from late Monday night through Wednesday, with perhaps more widespread precipitation occurring as another clipper system and cold front move through Wednesday ngiht into Thursday. A wintry mix of rain/snow is expected through this period. Mild temperatures are expected mid-week, with highs reaching into the 40s and lower 50s from Tuesday through Thursday. High pressure brings mainly dry conditions and seasonable temperatures Friday and Saturday.

AVIATION

for 18Z TAF Issuance Issued at 1258 PM CDT Sat Mar 21 2026

Showers were ending in far NE WI and mid-level clouds were rapidly eroding from west to east early this afternoon. Low stratus still covered parts of far NE WI, but this should mix out due to daytime heating and wind within a couple hours. Gusty S-SW winds will increase this afternoon, then diminish by sunset. Areas of LLWS will occur in spots, especially at RHI, GRB, ATW and MTW, then diminish by early evening.

Quiet weather will prevail this afternoon and early evening. A cold front will sink south tonight, bringing MVFR/IFR stratus. A band of light rain mixed with sleet will develop behind the front and shift south through early Sunday. The precipitation should start shortly before midnight in the far north, and exit the far south by mid-morning Sunday. Brisk north winds will also develop in the wake of the front, with gusts reaching 20 to 25 kts late tonight into Sunday morning.

Expect ceilings to gradually rise Sunday morning, though most places should remain in the MVFR category through 18z.

HYDROLOGY

Issued at 232 PM CDT Sat Mar 21 2026

As temperatures warm across the region, the snowmelt will result in increasing flows and rising river levels. Modeled snowpack temperature from the NOHRSC site points to widespread ripening of the snowpack, and higher susceptibility of melting. However, the lack of a prolonged significant warmup (and nighttime temperatures dropping below freezing most nights) points to a more gradual rise in area rivers as opposed to widespread rapid rise flooding. Some rivers will likely reach bankfull or even minor flood stage within the next couple days.

The flooding situation will be monitored closely given how much water is locked up in the current snowpack across the region. Fortunately, no significant precipitation events are expected over the next week, so nearly all of the runoff will be attributed to melting snow.

GRB WATCHES/WARNINGS/ADVISORIES

None.