FXUS63 KGRB 211020

AFDGRB



Area Forecast Discussion

National Weather Service Green Bay WI

520 AM CDT Sat Mar 21 2026



Updated aviation portion for 12Z 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 12Z TAF Issuance

Issued at 520 AM CDT Sat Mar 21 2026



High clouds streaming in across the region prevented much in the

way of fog from forming across the TAF sites early this morning,

with only a smattering of MVFR VSBYs noted. There is a slight 

chance for rain or snow across the far north this morning; 

however, this should remain well north of KRHI. Otherwise, VFR 

conditions are expected for the rest of today.



A cold front will sink south tonight, bringing a swath of light

rain and MVFR/IFR conditions to the TAF sites from north to 

south. As colder air filters in behind the cold front 

precipitation may transition to snow at KRHI; however, any 

snowfall amounts would be de minimis.



Winds will gradually veer to south/southwesterly throughout the

day, picking up slightly this afternoon. Gusts between 15 and 20 

knots will be possible. LLWs will become a concern late this 

morning and afternoon as winds just off the surface increase to

around 40 knots outof the southwest.



&&



.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.......Kurimski

HYDROLOGY......Kurimski