374
FXUS63 KGRB 061752
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1252 PM CDT Fri Jun 6 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- A couple rounds of light rain today, with a small chance of
  showers on Saturday.

- A cold front and upper low bring a higher chance for rain and
  thunderstorms on Sunday and Monday.

&&

.DISCUSSION...
Issued at 425 AM CDT Fri Jun 6 2025

Radar imagery shows ongoing light rain stretching from northern
Iowa into central WI early this morning, which is gradually
progressing east. There is another area of rain from northeast SD,
stretching across central MN and into far northwest WI. Both of
these are in association with fgen around 700mb and weak mid-level
shortwaves. Models show this forcing slowly weakening over the
course of the day, which will also lead to less shower coverage.

Expect this first batch of showers to move east through mid-
morning while simultaneously weakening. Then, the northern batch
moves into central/north-central WI late this morning, tracking
east through the afternoon. This is also expected to gradually
weaken with diminishing coverage. This double-batch of rain setup
does lead to prolonged PoPs across much of the forecast area, but
overall precip will be light and expect totals from a trace to
0.10" in most places, up to around 0.25" in north-central WI
(probably of getting at least 0.25" is 25%). Not expecting any
severe weather, but with 200-300 J/kg of CAPE today a few embedded
thunderstorms cannot be ruled out. Any remaining showers this
evening will diminish for the most part, but a few very isolated,
short-lived showers or sprinkles remain possible through the night.

Precip chances are lower on Saturday as there is not much forcing
to work with. A few widely scattered showers are possible (10-30%
chance, highest west), mainly during the afternoon due to daytime
instability.

The main event continues to be Sunday into Monday as a cold front
moves across the state followed by a potent upper low. As the
front comes through midday, this will sweep the initial round of
showers and thunderstorms from west to east across the area.
Severe potential looks modest at the moment, with MUCAPEs
generally peaking around 800 J/kg before the front moves through.
The forecast area gets in the dry slot for a bit, followed by more
rain and perhaps some thunderstorms Monday into Monday night as
the upper low moves overhead. Pwats peak around 1.00 to 1.25" on
Sunday, which is near or slightly above sounding climatology. So
do not anticipate flooding to be a much of a concern from this
system.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1252 PM CDT Fri Jun 6 2025

Isolated showers with a few rumbles of thunder developed over
north-central WI early this afternoon where an area of clearing
occurred late this morning. Elsewhere, SCT to BKN VFR clouds
prevailed. Anticipate the isolated showers and few rumbles of
thunder to continue to pop-up across north-central and far
northeast WI through the heat of the day before dissipating around
sunset. Have only included a TEMPO group at RHI for thunder until
20z Fri, but may need to remove or extend this as conditions
evolve. The central WI TAF sites are likely to see isolated rain
showers through the afternoon, but the thunder potential is less
certain due to continued cloud cover. How far eastward the
isolated showers track is also less certain due to the prevailing
cloud cover over the east-central WI TAF sites. Decided to
continue using PROB30 groups at ATW and GRB for this reason.

There is still a possibility for an isolated shower overnight into
Saturday morning, but confidence is not high enough to include at
any TAF site due to said isolated nature.

Patchy fog is possible late tonight, mainly in north-central WI,
but this is looking less impactful than previously forecast.

&&

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

&&

$$

DISCUSSION.....KLJ
AVIATION.......Kruk