791
FXUS63 KGRB 130347
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1047 PM CDT Sun Oct 12 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Gusty south/southeast winds will result in conditions hazardous
  to small craft on Lake Michigan through early Monday afternoon.

- Above average temperatures continue early this week, becoming
  slightly cooler mid-week.

- Light rain arrives tonight, lasting through Monday morning. Next
  widespread rain chances this weekend.

&&

.DISCUSSION...
Issued at 159 PM CDT Sun Oct 12 2025

GOES visible satellite and current obs show a north-south
oriented frontal boundary sitting over the northern Plains this
afternoon. Radar shows weak returns associated with agitated
cu popping across the forecast area, though there is no evidence
of any precip making it to the surface. Have thus decided to omit
near-term PoPs due to low confidence. Some CAMs try to pick up on
a signal for sprinkle activity over our western tier of counties
later this afternoon as an 850 mb LLJ draws moisture up ahead of
the front, though this activity would remain isolated in nature.

Rain chances... The decaying front is progged to make it into
Wisconsin late tonight, bringing with it widespread chances for
light rain late this evening through Monday morning. Thunder
chances will be near zero as instability fails to build along the
front. Unimpressive dynamics and deeper moisture still look to be
an issue as Canadian high pressure and reservoir of dry air build
in from the northwest. As such, grand ensemble continues to show a
meager 20 to 40% chance for receiving 0.25" of rain over north-
central Wisconsin. Omega block then establishes itself over the
CONUS mid-week, keeping us mostly dry heading into the weekend.
Only exception will be the potential for some sprinkles Tuesday
afternoon as weak shortwave energy rides along the upper ridge.
Long-range guidance then suggests the arrival of a more robust
system this weekend as a (closed-off?) upper low and lee cyclone
trek through the Midwest.

Temperatures... Temperatures remain above average today as a
steady stream of WAA affects most of the state. Most areas have
made it into the mid to upper 60s this afternoon, though cloud
cover has been a hindrance for some. This trend continues through
tomorrow, with a combination of downsloping post-frontal winds
and plentiful sunshine resulting in highs flirting with 70 degrees
near the Fox Valley. Stronger CAA then arrives on Tuesday, dipping
temperatures back into the 50s and 60s. Additional frost headlines
may be needed toward the end of the week, mainly as overnight
lows fall into the low to mid 30s over portions of far northeast
Wisconsin where the growing season continues. Will continue to
monitor in the coming days.

Marine... Winds ramp up out of the southeast this afternoon as the
pressure gradient tightens up ahead of approaching low pressure.
As a result, conditions hazardous to small craft are expected
along the nearshore waters of Lake Michigan through early Monday
afternoon as waves build to 3 to 5 ft. Gusts to 25 mph will be
possible during this time.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1046 PM CDT Sun Oct 12 2025

Scattered light showers ahead of a cold front will shift across
the area overnight. Showers will end before daybreak Monday over
central WI, and from the Fox Valley to the lakeshore by mid
morning. Rainfall amounts at any location will be light.
Conditions will mainly be VFR, except for a brief interlude of
MVFR cigs late tonight into Monday morning for portions of central
to north-central WI (mainly RHI).

Southeast winds veer south late tonight, gusting to around 20
kts at times. 40-50 kt low-level jet crossing the area will also
result in LLWS at all TAF sites through late tonight. As the rain
ends with the passage of the cold front Monday morning, winds will
become light out of the northwest.

&&

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

&&

$$

DISCUSSION.....Goodin
AVIATION.......JLA