537
FXUS63 KGRB 051846
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
146 PM CDT Fri Jun 5 2026

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- Scattered showers and storms are expected to cross the area from
  west to east through this evening. Some storms could become
  strong or severe, with damaging winds and up to 1" hail being
  the main concerns.

- Warm moist air moving across Lake Michigan will bring a period
  of marine dense fog across the nearshore zones, which may affect
  boaters.

- Above normal temperatures persist for the next week. High
  temperatures in the 90s along with humidity will increase the
  potential for moderate to major heat- related impacts.

&&

.DISCUSSION...
Issued at 146 PM CDT Fri Jun 5 2026

Storms This Afternoon/Evening...
Active weather will be the main focus of the forecast today.
Upstream development in Minnesota associated with a mid-level
shortwave is readily visible on both satellite and radar; and this
will be the main feature to watch for any stronger storm
development. Instability ahead of this feature has proved
sufficient for some isolated convection, mainly in the Upper
Peninsula, but will need to watch for at least isolated convection
developing out of the cumulus field across the northwoods. As the
storms progress into the region, modest lapse rates, weak shear,
and convergence along the shortwave could serve to provide a brief
hail threat, mainly limited further west where instability and
lapse rates will be greatest as the shortwave arrives. Wind then
becomes the more likely threat further east as scattered
thunderstorm activity heads into the and through the Fox Valley,
with CAMs suggesting the possibility of some brief bowing segments
embedded in scattered thunderstorm activity. Timing on storms
remains fairly similar to previous forecasts, with an arrival in
the mid to late afternoon for central and north-central Wisconsin,
and more of an evening timeframe for the Fox Valley. PWATs during
this time period remain fairly high (>1.5"), so moderate to heavy
rainfall will be possible within any convection., which may also
make for some fairly high localized rainfall totals for areas that
see the stronger storms. High end amounts could produce spots
with over an inch of rainfall.

Fog...
Fog over the marine zones will be in place this afternoon and
evening as the warm and moist airmass lifts northwards. Would
expected improvement as winds shift ahead of and along the
convection that will arrive from the west.

Temperatures...
Above normal temperatures will persist through the weekend into
next week, but a surge of even warmer temperatures will likely
(60-80% chance) bring high temperatures into the 90s by the middle
of next week. As this will be a several day stretch of warm high
temperatures and low temperatures also remain in the 60s, heat
related impacts are expected to see a major increase next week.
Warmest periods look to be Wednesday and Thursday afternoons,
where some of the higher potential 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 18Z TAF Issuance
Issued at 1257 PM CDT Fri Jun 5 2026

Lingering MVFR/VFR stratus and cumulus clouds will affect portions
of the region through the afternoon, especially along the Lake
Michigan shoreline and in north-central Wisconsin where increasing
instability has brought back some additional cumulus formation.

A round of rain and thunderstorms is then anticipated to cross the
region in the late afternoon and evening from west to east,
crossing into Wisconsin out of Minnesota. A few stronger storms
may be embedded within the line, with some hail potential in the
early afternoon turning to mostly a wind gust concern by the time
the storms reach the Fox Valley and lakeshore TAF sites. Exact
location of the stronger storms remains more uncertain at this
time, so kept the PROB30 group for now, but would expect to see
changes over to TEMPO and possibly prevailing as the storm
trajectories become more certain over the next TAF issuance.

Behind the storms, currently expect some clearing and better
flying conditions going into Saturday, so have VFR return by the
morning hours.

&&

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

&&

$$

DISCUSSION.....Uhlmann
AVIATION.......Uhlmann

NWS GRB Office Area Forecast Discussion