133
FXUS63 KGRB 241847
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
147 PM CDT Fri Jul 24 2026

.KEY MESSAGES...

- Hazardous boating conditions for small craft are expected on
  Lake Michigan and central Green Bay this afternoon through late
  tonight. There is also an increased risk of rip currents on
  Door County beaches adjacent to Lake Michigan.

- Heat and humidity will build across the region this weekend into
  early next week, with heat indices reaching the middle to upper
  90s on Sunday and Monday.

- Periodic chances for thunderstorms return late tonight through
  Monday. The highest potential for strong to severe storms is
  expected on Sunday afternoon and evening and possibly again on
  Monday.

&&

.DISCUSSION...
Issued at 145 PM CDT Fri Jul 24 2026

Tonight through Saturday night...

Lingering high pressure over WI will gradually get pushed out as
a front swings in from the west associated with a surface low
pressure in north central Canada. The front will swing in to the
western CWA Saturday morning with front weakening as it slides
southeast with the associated upper level shortwave. This will
carry some precip chances through the morning and perhaps
lingering into the afternoon. However, the best chances for
showers and especially storms will be focused further north. It
is worth noting that while models and CAMs do not show robust
convection but the underlying conditions suggest there is at
least a chances for some stronger storms due to elevated
instability in the morning and deep layer shear around 40-45kts
which is plenty to cause some severe concerns, primarily for
large hail concerns given the inversion in the low levels.

By the afternoon, as things become more unstable we will lose
most of the good surface and upper level forcing likely making
the afternoon into a largely dry period. A few CAMs pick up a a
few showers but clearly and lack of forcing and to some degree
moisture becomes a bit of a concern for any chances beyond the
morning. There is still a chance, which will need monitoring
given the good shear and instability, but the general trend
suggests drier. Into Saturday night there appears there may be
additional precip chances and even storm potential but there
remains quite a bit of uncertainty in the forcing with some mild
surface convergence and perhaps some upper level weak shortwave
energy, the question really becomes, will that be enough.
Elevated overnight showers across northern WI are more likely
overnight.

In addition, a Beach Hazards Statement remains in effect for
Door County from 4PM to 1AM tonight with waves around 3-4 feet
in the shoreline. There will be an increased risk for rip
currents along the shoreline later this afternoon and evening.

Sunday through Friday...

Focus then turns to Sunday and Monday which appear like decent
bets to produce some storms across parts of WI in the afternoon
and evening hours. They appear to be very similar days with very
similar forcings and environments at play. Sunday appears to be
slightly better given that it looks to have more going for it in
terms of forcing with a strong shortwaves and decent warm front
draped across the CWA with increasing LLJ and WAA into the
evening. Monday looks more focused along the front with less
support but likely enough support nonetheless. The instability
both days will likely climb to over 3000J/kg MUCAPE with
40-50kts of deep layer shear. Models have showed this mostly
impacting the eastern half of the CWA both days with more
westward extent Sunday. However, with all that we do know there
looks to be plenty of uncertainty still as we do not truly know
exactly where this front will set up and the progression of it
into Monday. This will be critical because storms will very
likely fire right along the boundary so where this boundary is
will determine where the impacts for storms will be. In any case
all hazards are possible with these events.

Increased uncertainty toward midweek but the upper levels
generally show the ridge reverting west a tad with weaker high
pressure over the region and several upper level shortwaves
rolling through. This suggests that things could very easily
become active for this period despite limited potential shown in
models at this time as no feature truly stands out at this
time.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1247 PM CDT Fri Jul 24 2026

Scattered to occasionally broken clouds are expected across the
region today as fair weather cumulus form across the area. These
should pose a minimal concern to aviation operations, so VFR will
stick around through the evening.

A cold front will approach from the north overnight, which could
bring some lower cloud across the north along with some
disorganized shower activity, affecting primarily RHI. Further
southwards these showers are expected to diminish rapidly, so
mention of showers was made at other sites for now.

Outlook...Scattered thunderstorms and lower flight categories are
possible at times over Saturday evening and again Sunday as a
warm and unstable airmass shifts into the region.

.KOSH...

Scattered 5-6 kft ceilings expected through the afternoon as fair
weather cumulus clouds hang around. These clouds should dissipate
again as we get into the late evening and overnight period.
Feature to watch overnight will be an approaching cold front early
Saturday, which should bring some disorganized showers into
northern Wisconsin. Currently expect these showers to dissipate as
they move southwards, with around 10-15% chance of some sprinkles
reaching the site, so did not add a mention of showers at this
time. That said, some increased cloud cover is possible fora brief
window in the afternoon. Fair weather cumulus then return for the
afternoon. Looking ahead of the current TAF period, Saturday
evening will also bear watching as it may include some pop-up
showers and scattered storms. Best signal remains west and
northeast of the area, but will need to monitor the forecast going
forward for convective potential over Oshkosh. Winds today will
remain out of the southwest at 5-10 kts with some brief gusts up
to 15 kts this afternoon before subsiding again tonight.

&&

.MARINE...
Issued at 145 PM CDT Fri Jul 24 2026

Winds will begin to increase this afternoon lower pressure beginning
to impinge on the high pressure that will increase the pressure
gradient over the northern portions of the lake. A relatively brief
period of higher winds on the northeast side of Lake Michigan is
expected. Small Craft Advisory in effect for much of the
nearshore and bay waters due to winds up to 25 kts and waves as
high as 4 feet from later this afternoon through much of
tonight.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
WI...Beach Hazards Statement from 4 PM CDT this afternoon through
     late tonight for WIZ022.
MARINE...Small Craft Advisory from 4 PM this afternoon to 4 AM CDT
     Saturday for LMZ521-541.
     Small Craft Advisory from 4 PM this afternoon to 10 PM CDT
     this evening for LMZ542-543.

&&

$$

DISCUSSION...
AVIATION...
MARINE...

NWS GRB Office Area Forecast Discussion