Suamico, Wisconsin Weather Forecast Discussion

808
FXUS63 KGRB 230012
AFDGRB
Area Forecast Discussion
National Weather Service Green Bay WI
712 PM CDT Mon Sep 22 2025
Updated aviation portion for 00Z TAF issuance
.KEY MESSAGES...
- Isolated showers and thunderstorms through early this evening.
- Areas of fog may develop on land again tonight. The fog could
  impact the Tuesday morning commute over portions of the area.
- Marine fog will be dense at times into Tuesday morning.
&&
.DISCUSSION...
Issued at 213 PM CDT Mon Sep 22 2025
Showers and Thunderstorms: Earlier convection that brought 30-40
mph wind gusts and heavy rain to Waushara County have shifted out
over Lake Michigan and has resulted in effective instability being
dampened out into early this afternoon. Instability is trying to
increase recently, but SBCAPES are still mainly less than 400j/kg
over the area. A few lightning strikes have developed northwest of
Green Bay, but higher res guidance/CAMs that are handling current
trends best, point to only isolated showers and storms through
end of peak heating late this afternoon. Risk of stronger storms
has diminished as greatest instability and re-inforced frontal
boundary have set up farther south over southern WI. SPC marginal
risk for severe is now completely out of our southern forecast
areas. Some potential for a few more showers and storms to drift
in late over the north from ongoing storms over Upper Michigan. By
mid to late evening, risk for storms will be finished over the
area as wave of sfc low pressure shifts east and a more stable
northeast flow spreads in from Lake Superior and Upper Michigan,
along with northern Lake Michigan.
Late tonight into Tuesday, cyclonic northeast low-level flow and
weak secondary shortwave dropping across may spur on a few more
showers over northeast and east-central WI. Minimal thunder expected
as instability will be on the wane, shifted farther south and east.
Dense Fog/Visibility: Fog that shrouded much of northeast WI and
the waters of the bay and Lake Michigan has cleared out. Exception
is over northern Lake Michigan and the bay around Washington
Island, where areas of fog remain. Models that are handling
fog/current visibility trends best point to fog lingering over
northern portions of the lake, with another round of expansion
over land areas later this evening and especially overnight.
Signal is not as definitive as what occurred for last night and
soundings point to mix of stratus and fog as there is a bit more
wind late tonight to mix very low levels. Will mention in HWO and
let evening shift assess potential for another Dense Fog Advisory.
Outlook beyond Tuesday...No high impact weather is expected as
pattern turns less active. Models and ensembles are back and forth
with how far north midweek low pressure system tracks. Blended
guidance has trended a bit lower for pops on Wednesday, but still
have some slight chances over east-central WI. Greatest instability
remains well displaced to the south/southeast, which should limit
the potential for thunderstorms during this period. By the end of
the week, a ridge is forecast to develop over Wisconsin, which
should bring dry conditions through the weekend. This ridging is
expected to continue into the start of next week. Temperatures
are forecast to remain at least slightly above normal right
through the first half of next week. Normal highs now are in the
upper 60s to near 70.
&&
.AVIATION...for 00Z TAF Issuance
Issued at 711 PM CDT Mon Sep 22 2025
Besides a low deck and fog slowly expanding over northern Door
County, VFR conditions prevailed across the region. This low deck
and fog will continue to expand southwestward late tonight, in
addition to a low deck dropping south from Lake Superior. As this
is occurring, there are also subtle indications of a few showers
developing in east-central WI roughly between 04 and 07z. Given
the low confidence, used a PROB30 at GRB/ATW/MTW. Otherwise, the
main impacts at all TAF sites for the remainder of the night and
into Tuesday will be the low stratus and fog with IFR/LIFR
conditions. Conditions will gradually improve from IFR to MVFR by
midday Tuesday, and eventually to VFR by late Tuesday afternoon.
However, RHI may continue to see MVFR cigs through all of Tuesday.
&&
.GRB WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION.....JLA
AVIATION.......Kruk

NWS GRB Office Area Forecast Discussion