NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 301211
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
711 AM CDT Sun Aug 30 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Isolated to scattered showers and storms throughout today and
  this evening. There is a low chance for additional showers and
  storms on Monday. If storms develop on Monday, they may become
  strong or severe, but details are uncertain at this time.

- Hazardous boating and swimming conditions on Lake Michigan
  through late this afternoon.

- Warmer, more humid conditions today and Monday. Heat indices
  may rise into the 90s Monday afternoon.

&&

.DISCUSSION...
Issued at 302 AM CDT Sun Aug 30 2026

Precipitation/Storm Trends...Isolated showers prevailed across the
region early this morning along an 850mb warm front/low-level WAA
gradient gradually lifting northeast across the region. Anticipate
this shower activity to continue into the afternoon, mainly across
the Northwoods. A few rumbles of thunder are possible within this
shower activity, mainly during the afternoon when a couple hundred
J/kg of CAPE will be present. Meanwhile, a weak surface front will
slowly lift into central and east-central WI throughout the day.
Just like with any warm front, CAMs are all over the place with if
convection will develop along this warm front. If any convection
develops along the front, central and east-central WI are the most
likely areas to see any shower/elevated storm activity. The surface
warm front will then lift north over the area tonight into early
Monday, allowing for additional shower/elevated storm activity to
continue overnight across the entire forecast area. Cannot rule out
the potential for a strong elevated storm capable of producing gusty
winds with MUCAPE between 1000-2000 J/kg and effective shear around
30 kts during the evening and overnight. These storms would be also
produce brief heavy downpours with PWATs around 2 inches during this
time.

After the shower/storm activity ends Monday morning, much of the day
should remain dry with weak capping in place. However, by late
Monday afternoon/evening, a surface low will track across northern
WI/Upper MI, which may spark some convection along its trailing weak
cold front in central and north-central WI if there's enough forcing
to break the weak cap. Models are not in agreement with this
convection developing, likely due to the capping. But will continue
to monitor this for severe weather potential as MUCAPE would be
around 1500-3000 J/kg and deep-layer shear of 30-40 kts.

Dry conditions return for Tuesday as the aforementioned cold front
weakens and sags south over southern WI. A couple shortwaves then
look to move over the region through the remainder of the work week,
bringing chances for showers and storms at times.

Temperatures/Humidity...As the warm front lifts north today, temps
will climb above normal for central and east-central WI into the
upper 70s to mid 80s, while temps will top out in the mid 70s across
the north due to the precip chances. Temperatures will be even warm
on Monday and Tuesday with highs in the mid to upper 80s, with a few
spots topping out around 90. The persistent southerly flow will
usher in humid conditions today and Monday as well, with dew points
increasing into the upper 60s and low 70s. Depending on cloud cover
and precip chances, heat indices on Monday may rise into the low to
mid 90s.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 711 AM CDT Sun Aug 30 2026

A low stratus deck, with LIFR cigs and IFR/MVFR vsbys, was
observed in north-central WI this morning, with MVFR cigs at the
central WI TAF sites, while the remainder of the area saw VFR
conditions. Additionally, isolated showers were observed across
north-central and far northeast WI this morning.

Anticipate conditions to gradually improve at the RHI TAF site to
IFR by mid-morning, and to MVFR by this afternoon, with the
isolated showers at times. Conditions will then briefly improve to
VFR at the RHI TAF site this afternoon before quickly falling back
to LIFR by this evening. The MVFR cigs in central WI this morning
may occasionally rise to VFR at times before becoming VFR during
the afternoon. The MVFR cigs will then return to the central WI
TAF sites late tonight. For the east-central WI TAF sites, VFR
conditions are expected through this TAF period, with the
exception of a brief period of MVFR cigs at the GRB TAF site this
morning.

Outside of the isolated showers across north-central and far
northeast WI this morning, there are indications of showers
becoming a bit more in coverage during the afternoon that may
reach all TAF sites. Used PROB30 groups when confidence is
highest.

Surface winds will be under 10 knots through the TAF period with
winds from the south in east-central WI and from the east in
central and north-central WI. Winds will become easterly at all
TAF sites overnight. There is also a period of LLWS anticipated
late tonight, impacting the central and east-central WI TAF sites.

&&

.MARINE...
Issued at 302 AM CDT Sun Aug 30 2026

Southerly winds around 10 to 20 kts this morning through this
afternoon will lead to increased waves along Lake Michigan to
around 2 to 4 ft, with some 5 ft waves. As winds turn more
easterly late this afternoon/evening, waves and winds will
subside. The onshore wave action will also generate a moderate to
high risk of rip currents along Lake Michigan beaches. Although
these conditions are marginally hazardous to small craft and
beachgoers, decided to issue Small Craft Advisories and Beach
Hazards Statements for today given the increased water traffic
this weekend.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement until 5 PM CDT this afternoon for WIZ022-
040-050.
&&

$$

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