367
FXUS63 KGRB 140257
AFDGRB

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

Updated aviation portion for 06Z TAF 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...for 06Z TAF Issuance
Issued at 955 PM CDT Wed Aug 13 2025

Few-Sct cu and stratocu linger through the night, especially over
far northeast WI. May also see higher clouds from the west. Fog
is possible late tonight with high pressure overhead, especially
over central and north-central where coolest temps are expected.
Kept the mention of LIFR vsby at RHI and IFR/MVFR at AUW/CWA.
Patchy, brief MVFR ground fog could occur elsewhere. Hint that
smoke over northern Lake Michigan and lower Michigan may try to
shift across northeast WI in the morning. May need to add to TAFs
eventually based on upstream observations. Not clear cut though.
Light and variable winds tonight will become southerly on
Thursday.

&&

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

&&

$$

DISCUSSION.....KLJ
AVIATION.......JLA