022
FXUS63 KGRB 291839
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
139 PM CDT Sat Aug 29 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Large area of rain showers continues to spread across the area
  this afternoon, with additional isolated-scattered showers
  tonight. Rumble of thunder possible, mainly tonight.

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

- Warmer, more humid conditions, and thunderstorms chances arrive
  Sunday into early next week. There will be a threat for some
  strong to severe storms, but details on where and when remain
  elusive. Heat indices may rise into the 90s Monday afternoon.

&&

.DISCUSSION...
Issued at 139 PM CDT Sat Aug 29 2026

Showers/Storm Trends...Area of light to moderate rain continues
to trek across the region this afternoon as a mid-level shortwave/
trough and weak surface warm front move through. This area will
shift to the east by around sunset, with additional more isolated
to scattered shower activity expected later this evening into
Sunday morning as another frontal boundary lifts northward and
weak WAA/moisture advection occurs. Lack of instability has not
allowed for any thunder today. Slightly better chance for some
thunder tonight as elevated CAPE spreads in from the south/west,
so will continue with a slight chance of thunder. PWATs do climb
to around 2 inches overnight, but any heavier rain looks to be
very isolated with chances of over an half inch of rain under 50%.

On Sunday into Tuesday, most of the period is looking dry, but as
instability builds in the warm sector with a surplus of moisture
and instability, especially on Monday (MUCAPE of 2000-3000 J/kg),
along with the stationary boundary in the region and possible
weak shortwaves crossing the region, storms will be possible at
times. But a weak cap will help keep a lid of storm activity. Not
surprisingly, CAMs and other models are all over the place with
location/timing of storm chances. AI/ML highlighting much of the
area for an increased threat for severe storms somewhere in this
timeframe, but pinning down when will be challenging. So a lot of
if`s, but if anything can form, it could be on the strong or
severe side with gusty winds and hail possible, along with
torrential downpours. Will need to monitor these features and
trends over the next few forecast runs to better assess the
severe weather threat.

Temps & Humidity Levels...The clouds and rain kept high temps
below normal today, mainly in the 60s to low 70s. As the warm
front lifts north, temps will climb 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 with a few spots topping out
around 90. The south flow will usher in humid conditions on
Sunday 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 18Z TAF Issuance
Issued at 1219 PM CDT Sat Aug 29 2026

Large area of light to moderate rain will continue to spread
across the region this afternoon, with mainly VFR and MVFR
conditions. As this first area of rain exits to the east late this
afternoon, additional showers are possible this evening into
Sunday morning, but coverage looks to be more isolated-scattered.
Will use TEMPO/PROB30 groups for this secondary area of showers.
While a rumble of thunder can`t be ruled out, thunder chances
remain very low (under 20%) so will not include in any TAF. Brief
MVFR conditions are possible at GRB/ATW/MTW, but VFR should
prevail for most/all of the TAF period. The VFR/MVFR conditions
will continue for AUW/CWA with some IFR conditions possible around
sunrise on Sunday. At RHI, look for conditions to drop to IFR/LIFR
overnight and into Sunday morning. CIGs and VSBYs will slowly
improve Sunday morning. Some patchy fog will be possible
overnight into early Sunday as well, lower VSBYs at times,
especially across central and northern WI.

Winds will generally be out of the south or southeast through the
TAF period. A few gusts to ~15 kts are possible this afternoon,
with winds under 10 kts expected tonight into Sunday morning.
Marginal LLWS is possible, mainly south of Hwy 29, this evening
into early Sunday as southwest winds increase to 30-35 kts.

&&

.MARINE...
Issued at 139 PM CDT Sat Aug 29 2026

Southerly winds will steadily increase late tonight into Sunday,
with sustained winds at 10 to 20 knots along Lake Michigan. These
persistent southerly winds will build wave heights to 2 to 4 feet
along the Lake Michigan nearshore waters, with some 5 ft waves
possible, possibly bringing hazardous conditions for small craft.
The onshore wave action could also generate an enhanced risk of
rip currents along Lake Michigan beaches. Due to slightly lower
winds, the wave forecast has decreased a little, hovering around 4
ft, so will wait to see the latest wave model forecast before
deciding on any Small Craft Advisories or Beach Hazard Statements.

&&

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

&&

$$

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

NWS GRB Office Area Forecast Discussion