NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 311828
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
128 PM CDT Tue Mar 31 2026

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Rain showers expected this morning through the mid-afternoon. A
  few thunderstorms are possible, mainly in east-central WI. If a
  stronger storm were to develop, hail would be the main threat.

- Winter weather impacts are likely Wednesday into Thursday, with
  both ice and snow accumulations possible. However, confidence in
  amounts remains low due to uncertainty in storm track. Another
  chance for winter weather impacts is forecast Friday into
  Saturday.

- Hydro concerns arise this weekend into early next week
  following the passage of two moisture rich systems.

&&

.DISCUSSION...
Issued at 510 AM CDT Tue Mar 31 2026

Rain/Storm Chances through this Afternoon...A low-level trough is
progged to move east across the region this morning into this
afternoon. Despite the surface low and surface warm front remaining
south of the forecast area during this time, some CAMs are depicting
isolated convection developing along the elevated CAPE and mid-level
lapse rate gradients over east-central WI sometime this morning
ahead of the low-level trough passage. If these isolated storms
develop, there is potential they could produce hail, similar to the
storms that occurred last night. As the low-level trough slides
east/southeast over the area at the same time, much of the forecast
area will see a broken line of rain showers. Any precipitation will
exit the forecast area to the southeast by around 4 PM this
afternoon.

Two Moisture Rich Systems Midweek and Late this Week...Following a
break in the precipitation from tonight through much of Wednesday, a
Colorado Low brings the next chance for precipitation late Wednesday
through late Thursday. With the Gulf open, this system will bring
warmer, moist air to the area, with PWATs of 1-1.25 inches. While
there is agreement for this system to bring winter impacts to the
forecast area, with indications of all p-types being possible at
some point, uncertainty remains in low track and surface
temperatures. The latest guidance does indicate a slightly northerly
track, which lowers the potential for snowfall amounts, but,
increases the potential for ice accumulations. As such, there is
generally a 30-50% probability for ice accumulations to reach 0.25
inches for locations in central and north-central WI. But, given the
remaining uncertainty, decided not to issue any winter headlines at
this time. If guidance continues to indicate a low track similar to
the latest runs, much, if not all, of the forecast area would be
under a winter headline with significant icing impacts being
possible.

Right on this system's tail will be another Colorado Low progged to
move over the region late Friday into Saturday. This system will
also bring warmer and very moist air to the region, as the Gulf will
still be open for business. Similar to the midweek system, there are
uncertainties in low track and thermal profiles.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 122 PM CDT Tue Mar 31 2026

Thunderstorms were shifting SE of the region early this afternoon,
and weather conditions are expected to be quiet for the TAF
period. The main concern will be low cloud trends. MVFR and
localized IFR condiitons were ongoing over the far north and east,
and these should erode later this afternoon or evening. Models are
hinting at another chance of low clouds later tonight into
Wednesday morning and have added some MVFR ceilings into the TAFs
during that period.

North winds will become NE-E and become gusty later tonight into
Wednesday.

&&

.HYDROLOGY...
Issued at 510 AM CDT Tue Mar 31 2026

Despite the uncertainty in p-types, the two well-saturated
systems this week will lead to hydro concerns, with a signal for
river and stream rises this weekend into early next week across
the forecast area. Minor flooding would likewise be possible in
low-lying and poor drainage areas.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION.....Kruk
AVIATION.......Kieckbusch
HYDROLOGY......Kruk