723
FXUS63 KGRB 021143
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
543 AM CST Mon Mar 2 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- A more spring-like pattern sets up this week with chances for
  very light mixed precip tonight into Tuesday (15-30%), then
  mainly rain mid-week (20-55%) and again late in the week
  (60-80%). Chance for storms arrives on Friday, mainly south.

- A gradual warming trend begins today and continues through the
  week. Ice jam/floe, minor flooding and fog concerns may arise.

&&

.DISCUSSION...
Issued at 219 AM CST Mon Mar 2 2026

Precipitation Chances...Dry conditions will prevail today as high
pressure shifts east of the Great Lakes. Then, as a zonal flow
sets up across the CONUS, there will be periodic chances for
precip through the rest of the week and into the weekend as pieces
of shortwave energy and low pressures traverse the northern
CONUS. The first chance arrives late tonight into Tuesday morning,
as weak mid- level FGEN and WAA spread into the state. Overall
forcing will be lacking, with the better FGEN and moisture to our
south, along with some low-level dry air to overcome. NBM/HREF/REFS
probs of 0.01" running under 40%, with under 20% of more than
0.05", highest south. Will continue to only carry low-end PoPs of
15-30% south of Hwy 29. While any precip will be light, temp
profiles will be hovering near 0C up to ~5000 ft, with a warm nose
likely present for at least part of the period. This would bring
some freezing rain and mixed rain/snow into the picture. Any
impacts would come into play if the freezing rain (or possible
freezing drizzle if sufficient saturation occurs) were to occur,
but this threat looks too low right now to highlight.

The next chance for precip arrives late Wednesday into Thursday a
a slightly stronger shortwave/low pressure crosses the Great
Lakes. Still some disagreement on the strength and rain coverage,
but model consensus holds PoPs of 20-55%, highest across east-
central WI. Won`t include any thunder, but some weak instability
will sneak into into southern WI so will need to monitor for any
northward shift.

The strongest system is set to arrive Friday into Saturday as a
deeper trough and strong upper jet approach the region. Model
uncertainty remains regarding the details of the trough and jet
this far out, but NBM PoPs of 60-80% signaling a good chance for
rain, especially with strong SW flow setting up ahead of the
system and an open Gulf ushering in some pretty beefy PWATS over
an inch (near the 99th percentile) into the region. The ultimate
track/strength of the low will determine if/where pockets of
heavier rain can make it into our area. GEFS probs of over 0.5" of
rain only running between 15-40% south of Hwy 29 for now, but
will see if these values creep up. Will need to monitor how far
the warm front can get, as some heavier rain could set up along
it. Thunder threat has shifted northward into the Fox Valley, but
severe weather guidance/probs are focusing any severe threat south
of our area.

Temperatures...Zonal flow will usher in modified Pacific air into
the Great Lakes, allowing temps to slowly moderate through the
week. High will mainly be the 40s (a few upper 30s today), and
into the 50s for some spots especially on Friday and/or Saturday.
Friday is looking to be the warmest day of the week based on
current timing, with the potential for some spots to reach 60
degrees. The lack of snow cover over parts of the area would
favor the warmer air getting a little further north. However,
cloud cover could hinder temps, along with a SE flow over the
chilly waters of Lake Michigan holding temps down over far eastern
WI. NBM/LREF probs of 60+ are below 20% so will not have any 60s
in the forecast for now.

Fog Potential...Chances for fog will increase through the week as
dewpoints increase and snow melt adds to the low-level moisture.
The greatest potential for fog development will be across central
and northern WI where the greatest snowpack remains, and when
winds will be light with mostly clear skies.

Minor Flooding and Ice Jam/Floe Potential...In general, the
threat for flooding this week will be very low as temps will be
above freezing during the day and below freezing at night,
allowing for a slow melt which will chip away at the remaining
snowpack. The flooding threat would increase late Friday into
Saturday, if/where a heavier area of rain were to occur, as 10-20"
frost depths will limit how much rain will be able to soak into
the ground. The ice jam threat will increase through the week as
many rivers are still fully or partially ice covered and the
warmer temps and increasing flows will promote additional break
up. However, the ice jam threat will be reduced a little due to
the rivers running pretty low.

Gusty south/southwest winds today will increase the threat for
ice floes on Green Bay as well. Latest satellite imagery showing
some open water over pats of the northern Bay and some thinning /
possible breaks in the ice over the southern and central Bay. Hard
to tell if any of the ice south of Chambers Island is movable
right now, but will error on the cautious side and add this
threat to the HWO. Depending on how strong the system on
Friday/Saturday is, another threat for ice floes may develop,
especially with additional melting/thinning of the ice through the
week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 543 AM CST Mon Mar 2 2026

VFR conditions will prevail today as patches of mid-clouds move
across the region. A chance for mixed precip, including light
rain/snow and freezing rain/drizzle, arrives late tonight into
Tuesday morning. Uncertainty remains on where/if enough saturation
will occur for any mixed precip to occur, so have not included
any precip in this TAF issuance, but will bring in some MVFR
ceilings into central and north-central WI as the lower clouds
will arrive there first. Some patchy fog will be possible across
north-central WI overnight into Tuesday morning as well.

Any LLWS across far north-central WI will end early this morning.
South to southwest winds will increase this morning and gust to
20-25 kts through the afternoon, then becoming light and variable
tonight. LLWS may return overnight across north-central WI, but
will hold off on including as it looks too marginal.

&&

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

&&

$$

DISCUSSION.....Bersch
AVIATION.......Bersch

NWS GRB Office Area Forecast Discussion