485
FXUS63 KGRB 132047
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
347 PM CDT Wed Aug 13 2025

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- A slight uptick in humidity Thursday, but still quiet weather.

- On and off chances for heavy rain and thunderstorms from Friday
  night through Monday. Strong or severe storms may also be
  possible at times.

&&

.DISCUSSION...
Issued at 345 PM CDT Wed Aug 13 2025

Quiet weather expected for the rest of today and tomorrow with
surface high pressure over the area today slowly shifting east
tomorrow. Most of the daytime cu which has formed today should
dissipate after sunset, but may linger in the far northeast
overnight. With mostly clear skies and light winds localized,
patchy fog is possible late tonight which could produce some lower
visibilities for drivers, primarily in central and north-central
WI.

Surface obs do not show any vsby restrictions from smoke today,
but there is a narrow area of near-surface smoke across WI as
noted by moderate air quality and smoke models. Kept a little bit
of smoke in the grids, based on the HRRR, through tomorrow as it
is noticeable by scent, and a very slight haze to the sky.

The pattern changes Friday and into early next week with an upper
ridge building across the Upper Mississippi River Valley and
southerly flow from an open Gulf. This will transport up a
significant amount of moisture, with Tds in the upper 60s/low 70s
and pwats generally ranging from about 1.6-2.1". At the surface, a
slow moving cold front will move sagging south across WI from late
Friday though Saturday night. And a LLJ is also pointed right at
the area Friday night into Saturday morning, and possibly again
late Saturday into early Monday. This setup is favorable for a
complex or two to develop and move across the general area, but
models often struggle to determine exact timing and placement
until much closer to the event. Given the high pwats, heavy rain
is likely within any thunderstorm complex/MCS. With CAPE values of
1500-2500+ J/kg strong to severe storms may be possible at times,
too.

Drier and less humid weather is likely to return in the Tue/Wed
time frame as models show the upper ridge breaking down and high
pressure building back at the surface.

&&

.AVIATION.../18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1157 AM CDT Wed Aug 13 2025

Scattered to broken mainly VFR cumulus will continue to develop
this afternoon. Have continued to omit any smoke mention for now
with upstream observations not showing any visibility
reductions. Overnight tonight/early Thursday, some patchy
IFR/MVFR fog/stratus may develop in spots, highest chances
(40-70%) across central and north-central Wisconsin and along
Lake Michigan. Light northerly winds will shift southerly on
Thursday.

&&

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

&&

$$

DISCUSSION.....KLJ
AVIATION.......JM