888
FXUS63 KGRB 051130
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 AM CDT Fri Jun 5 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Scattered showers and storms are expected over much of the area
  this afternoon and evening. Some storms could become strong or
  severe, with damaging winds and up to 1" hail being the main
  concerns.

- Above normal temperatures persist for the next week. Chance for
  highs in the 90s increases early next week, along with
  potential for moderate to major heat-related impacts.

&&

.DISCUSSION...
Issued at 109 AM CDT Fri Jun 5 2026

Rain/storm chances... Severe weather threat remains on track for
this afternoon/evening as driving shortwave treks over the
northern Plains and cold FROPA makes it into Wisconsin. Subsidence
behind a line of showers over northeast Wisconsin late tonight
has been efficient in clearing out skies to our west, which, if
trends hold, would be conducive for destabilization this
afternoon and evening. Increasing bulk shear (30 to 35 knots) and
steepening lapse rates (7 to 9 C/km) occur during this time as
well, which could lead to development of some stronger updrafts as
they coincide with peak heating. CAMs seem to latch onto a signal
for convective initiation to occur somewhere over central
Minnesota late this morning, before rapid upscale growth into a
line segment/QLCS occurs Friday afternoon before reaching
northeast Wisconsin. In this scenario, damaging wind gusts would
be the primary concern as the low-level jet ramps up. Hail up to
1" would be a secondary concern given steep lapse rates and
elongated hodographs. Periods of moderate to heavy rain will
accompany any stronger convection as PWATs reach around 1.5" (90
to 95th percentile), with WPC highlighting mainly east-central
Wisconsin in their Excessive Rainfall Outlook.

Temperatures... Temperatures will remain well above average over
the course of the next week as synoptic flow re-amplifies and
building heat ridge/Hudson Bay high set us up under southerly flow
regime. Potential for heat-related impacts drastically increases
during the early to middle part of next week, with probabilities
for 90-degree highs sitting at a widespread 50 to 80%. Ample
moisture transport from an open Gulf will likewise cause dewpoints
to rise solidly into the 60s, which would put us under a level 2
out of 4 (moderate) risk for heat-related impacts early next week,
increasing to level 3 out of 4 (major) by mid-week. Warmest
periods look to be Wednesday and Thursday afternoons, when heat
indices are forecast to exceed 100 degrees across portions of
central Wisconsin to the Fox Valley. Though still too soon to say
with certainty, will need to monitor the potential for headlines
as we head into early next week.

Extended... Accompanying the heat and humidity next week will be
a reservoir of instability that builds over much of the upper
Midwest. However, predictability for any rain/storm chances
remains low this far out as mid-level ridge sits right overhead.
Most of the ridge rider activity looks to stay off to our west,
so convective initiation in our neck of the woods would likely
hinge on smaller scale forcing mechanisms given the general
absence of upper support. This being said, cannot rule out
periodic chances for some stronger diurnal storms given the
magnitude of destabilization likely to occur during peak heating.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 630 AM CDT Fri Jun 5 2026

Patchy light showers linger around GRB/ATW/MTW early this
morning, but VFR/MVFR conditions prevail. Ceilings at AUW/CWA/RHI
should gradually improve over the next few hours.

Another round of scattered thunderstorms will likely (70% chance)
develop across western Wisconsin this afternoon and move over the
central Wisconsin airports starting around 21Z, so TEMPO groups
were introduced there. Somewhat lower confidence in thunder at
GRB/ATW/MTW after 00Z so PROB30 groups were maintained. Any
thunderstorms will bring a threat of small hail, gusty/variable
winds, and heavy rain bringing brief IFR/LIFR conditions.

Otherwise, a period of IFR ceilings/visibility will be possible
at AUW/CWA/RHI overnight.

&&

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

&&

$$

DISCUSSION.....Goodin
AVIATION.......KS

NWS GRB Office Area Forecast Discussion