634
FXUS63 KGRB 300449
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1149 PM CDT Sat Aug 29 2026

Updated aviation portion for 06Z TAF 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 06Z TAF Issuance
Issued at 1149 PM CDT Sat Aug 29 2026

Isolated to scattered showers are possible into Sunday morning,
with TEMPO/PROB30 groups to cover this activity. 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 IFR/LIFR conditions 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.

Surface winds will generally be light, below 10 knots through the
TAF period.

&&

.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.......Kurimski
MARINE.........Bersch