888
FXUS63 KGRB 290742
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
242 AM CDT Sat Aug 29 2026

Forecast discussion for routine morning forecast issuance

.KEY MESSAGES...

- Rain showers to spread across the area this morning into this
  evening. Most locations to see at least 0.20" with the greatest
  potential for localized heavy rainfall (0.50-1") across the
  Northwoods.

- Hazardous boating and swimming conditions on Lake Michigan from
  late tonight through Sunday evening.

- Becoming warmer and more humid Sunday into early next week. Heat
  indices may rise into the 90s Monday afternoon.

- Thunderstorms possible at times from Sunday into early next
  week. It is too early to determine if any of the storms would
  become severe from Sunday through Tuesday.

&&

.DISCUSSION...
Issued at 241 AM CDT Sat Aug 29 2026

Precipitation Trends...The forecast area remains on tracks to see
widely scattered rain showers today as a mid-level shortwave/trough
and weak surface warm front sweeps across the region. Although deep-
layer shear will be around 30-40 kts, a lack in instability (only
around 100 J/kg) will limit thunderstorm chances to only a few
rumbles of thunder at times. As the main area of rain gradually
departs the region to the northeast late this evening, another warm
front will begin to lift into central and east-central WI. Models
seem to be in decent agreement this front will produce additional
isolated/scattered showers and perhaps some elevated storms in these
areas before these showers/storms and the showers in far northeast
WI exit by Sunday morning. PWATs will mainly be in the 1.50-1.75
inch range, but will increase to 1.75-near 2.00 inches with the
arrival of the secondary warm front. CAMs/short-range models
indicate the axis of heaviest rain (0.50-1.00 inches) will be across
the Northwoods, while mid to long-range models indicate the axis
will extend from central into east-central WI. However, ensembles
are trending towards the short-range model solution. Leaned more
towards this solution given the agreement/trends.

The warm front will gradually lift north on Sunday and become nearly
stationary over the area on Monday as an upper-level ridge resides
overhead. This will leave the forecast area in the warm sector with
a surplus of moisture and instability, especially on Monday (MUCAPE
of 2000-3000 J/kg). Models are in disagreement in precip chances for
Sunday, but the greatest chances should remain focused along the
warm front as it lifts north. For Monday, despite the surplus of
moisture and instability, mid-level capping may prevent any
convection from developing. However, there are some signs of a cold
front/shortwave moving over the area sometime later in the day on
Monday, which would present the opportunity for showers and
storms, including strong/severe, to develop. Will need to monitor
these features over the next few forecast runs.

Depending on where/when the aforementioned cold front moves over
the region, models are in some agreement with the front dropping
somewhere over the state and remaining nearly stationary, leading
to additional chances for showers and storms on Tuesday. Another
shortwave then looks to move over the region sometime midweek,
bringing more chances for showers and storms.

Temperatures...Highs will be a few degrees below normal today due to
the anticipated rain/cloud cover, with values in the low to mid 70s.
Temperatures will then rise above normal on Sunday into the upper
70s to mid 80s, and even warmer on Monday and Tuesday with highs in
the mid to upper 80s, due to the persistent southerly flow. This
flow will also result in the return of humid weather on Sunday and
Monday as dew points increase 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. Mother Nature is reminding us
summer isn`t over yet.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1034 PM CDT Fri Aug 28 2026

Clouds will thicken and lower overnight ahead of an approaching
mid level shortwave. Patchy fog is possible over far northeast WI
late tonight, with minimal impacts to the terminals.

Rain chances increase Saturday morning as the aforementioned weak
shortwave and warm advection move into the region. Rain arrives
at KRHI/KAUW/KCWA between 10Z-12Z Sat, reaching KGRB/KATW/KMTW
around 14Z-16Z Sat. MVFR ceilings and visibilities will develop in
steady rain with IFR ceilings possible across north-central
Wisconsin. Thunder chance remains 

NWS GRB Office Area Forecast Discussion