FXUS63 KGRB 211812

AFDGRB



Area Forecast Discussion

National Weather Service Green Bay WI

112 PM CDT Sat Mar 21 2026



Updated aviation portion for 18Z TAF issuance



.KEY MESSAGES...



- Snowmelt will cause increased flows and rising levels on rivers

  and streams. Several rivers may reach bankfull or even minor 

  flood stage beginning this weekend.



- Rain (30-50% chance) tonight into Sunday morning. Rain may 

  briefly mix with snow or sleet before ending, but little or no 

  accumulation is expected. 



- Well above normal temperatures expected today, especially in

  central Wisconsin, where highs could reach well into the 60s and

  possibly 70 (20-40% chance). Mild readings into the 50s are 

  also anticipated next Tuesday and Thursday.



- A wintry mix of precipitation possible during the middle of 

  next week, especially Wednesday into Thursday.



&&



.DISCUSSION...

Issued at 1255 AM CDT Sat Mar 21 2026



Some patchy fog and stratus will impact the region this morning

with light winds and low-level moisture from melting snow. Once

the fog dissipates, there will be a small (10-30%) chance for 

rain or freezing rain this morning in response to isentropic lift 

in a moisture starved air mass.



Today will likely be the warmest day of the week as an 

approaching low pressure system from the Northern Plains brings a 

warm front and associated surge of very mild air into the forecast

area. This warmth will primarily be felt in central Wisconsin, 

where there is a 60-80% chance of highs greater than 65 degrees 

and a 20-40% chance of highs hitting 70 degrees across the far 

southwest corner of the region. Farther north and east, a 

combination of low clouds (north of the warm front) and SE-S winds

off Lake Michigan will keep readings in the 40s and 50s.



As the low shifts east, a cold front will sweep through the

forecast area during the late afternoon/evening. Models show

strong mid-level FGEN forcing with this system, which should

bring a band of light rain through the area tonight into early 

Sunday. This band should sag southeast with time, with the lagging

influx of colder air only leading to a brief period of mixed 

precipitation (mainly sleet/snow) on the northwest periphery of 

the precipitation band. Therefore, not expecting much (if any) 

snow accumulation. Most of the precipitation should be gone by 

Sunday afternoon.



High pressure will then provide mainly dry weather and more

seasonable temperatures from Sunday afternoon through Monday

night. Another clipper system will move through during the middle

of next week. This system looks fairly similar to this weekend's

system, with potential for a light mix of rain/snow, especially

Wednesday into Thursday. Mild days occur ahead of the clipper on

Tuesday, and within a dry slot on Thursday, with potential for

50s both days.



&&



.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 1255 AM CDT Sat Mar 21 2026



As temperatures warm across the region, the snowmelt will result

in increasing flows and rising river levels. Some rivers could

reach bankfull or even minor flood stage starting this weekend.

The lack of a prolonged significant warmup points to a more

gradual rise in area rivers as opposed to widespread rapid rise

flooding. That being said, the flooding situation will be

monitored closely given how much water is locked up in the

current snowpack across the region. Modeled snowpack temperature

from the NOHRSC site points to widespread ripening of the

snowpack (and higher susceptibility of melting/runoff) over the

area today.



&&



.GRB WATCHES/WARNINGS/ADVISORIES...

None.



&&



$$



DISCUSSION.....Kurimski

AVIATION.......Kieckbusch

HYDROLOGY......Kurimski