208
FXUS63 KGRB 191134
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
634 AM CDT Sat Apr 19 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Widespread precipitation arrives Sunday afternoon/night into
  Monday with rainfall totals of 0.50-1.25" for most locations.
  Some river rises are expected, but widespread flooding not
  expected.

- The rain will mix with snow across north-central Wisconsin
  Monday afternoon and Monday night, but little to no accumulation
  is forecast.

- Cooler temps arrive to start the new week, but a warm up is on
  tap by Wednesday, with periodic rain chances through the week.

&&

.DISCUSSION...
Issued at 351 AM CDT Sat Apr 19 2025

Precip Amounts / Trends:

Light rain showers and mist/drizzle will exit the area early this
morning. A few lingering sprinkles/flurries will remain possible,
mainly over northern and far northeast WI today. No impacts
expected.

Low pressure and potent negatively tilted shortwave will move
across the Plains on Sunday and track into the western Great Lakes
on Monday. A large swath of rain will spread across the area from
south to north Sunday afternoon/evening as moisture (PWATs to
around 1") and isentropic lift increases. Precip tapers off on
Monday as the low departs. Rainfall totals of 0.50-1.25" are
expected for most of the area, highest across central WI, where
probabilities for over an inch have increased to 50-70%. As the
column cools on Monday, a switch over to a rain/snow mix or
possibly all snow for a time is expected across north central WI.
However, the bulk of the heavier precip will be exiting, which
will limit the likelihood of any accumulating snow. Probability of
a half inch of snow in Vilas Co is hovering around 50%, with the
chance of 2 inches or more only 5-15%. The higher totals would
occur if a slightly southeast track occurs and boundary layer
temps are a couple degrees cooler. Will hold off any snow
accumulation in the official forecast, as the wet/warm ground,
along with the strong mid-April sun, will make it difficult for
the snow to accumulate. If any accumulations were to occur, it
would mainly be on grassy surfaces with little to no impacts on
the roads.

Another system arrives Tuesday afternoon/evening, bringing more
rain chances to the area. This will be a weaker system with much
less moisture and forcing. Additional chances for rain, along with
a few storms, will occur in the mid-late week period. But quite a
bit of uncertainty exists on where a frontal boundary will set
up, along with with/when any low pressure systems would track into
the region. Had to stick with the broad-based 20-40% chances for
much of the mid-late week period until more there is more clarity
on how things will play out.

Hydro / Fire:

With parts of central and east central WI receiving 0.75-1.50" of
rain over the past couple of days, many rivers will be on the
rise. The additional rainfall late Sunday into Monday may keep
some river levels high, but widespread hydro issues are not
expected.

As drier air filters into the region this weekend, conditions will
start to dry out. RH`s are forecast to drop into the 30s and 40s
for much of the area, away from Lake Michigan. A few spots in the
sandy soil regions of central and north central WI could see RH`s
drop into the upper 20s during peak heating. But overall fire
concerns will be held in check due to recent rain / unsupportive
fuels, temps in the 50s, and winds staying mainly under 20 mph.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 634 AM CDT Sat Apr 19 2025

Other than an isolated sprinkle or flurry over northern WI this
morning, look for dry conditions. A mix of VFR/MVFR/IFR conditions
early this morning will improve to VFR by this afternoon.
Some lower clouds will be possible early Sunday morning as flow
turns to the southeast, but confidence is low on if they will
occur. Patchy fog will also be possible, especially north and
west of the Fox Valley.

West/northwest winds will gust up to 20 kts today then diminish
and become variable this evening. Winds will shift to the
east/southeast Sunday morning.

&&

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

&&

$$

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