NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 061130
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 AM CDT Sat Jun 6 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Warm moist airmass moving over Lake Michigan may bring a period
  of marine dense fog across our nearshore zones this morning,
  which could affect boaters. Patchy fog will also be possible
  over land.

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

- Next chance for widespread showers will be Monday into Tuesday.

&&

.DISCUSSION...
Issued at 1247 AM CDT Sat Jun 6 2026

Tranquil conditions on tap for today as subsidence behind early
morning showers has effectively cleared out skies to our west.
Daytime instability should produce a fair weather cumulus field
across much of the area late this morning through this afternoon.
Highs will be around 5 to 10 degrees above normal, reading in the
low to mid 80s.

Fog... CAMs continue to latch onto a signal for fog, locally
dense, re-developing over land and water this morning as warm and
moist airmass continues to lift north. Marine Dense Fog Advisory
remains in effect, though there remains uncertainty with how far
into our nearshore zones the fog will make it due to offshore
flow.

Temperatures... Warming trend continues for next week as heat
ridge builds and Hudson Bay high sets us up under southerly flow
regime. Result will be a prolonged stretch of 90+ degree days,
with little relief into the overnight periods. Confidence remains
high (generally 60 to 90%) for seeing highs in the low to mid 90s
Wednesday through Friday as ample moisture transport increases
dewpoints solidly into the 60s and even 70s. As such, heat indices
will largely read in the mid to upper 90s, with several readings
in excess of 100 degrees possible across portions of central
Wisconsin to the Fox Valley. Widespread major (level 3 out of 4)
risk for heat-related impacts are forecast during this period,
which would affect those without a means for cooling or
hydration. Though still too soon to say with certainty, will need
to monitor the potential for headlines as we head into early next
week.

Extended... Next chances for widespread precip arrive Monday into
Tuesday as a fairly potent shortwave migrates through prevailing
southwesterly flow and up into the Midwest. Can expect some
periods of heavy rain during this time as PWATs approach 2" (99th
percentile), though any organized convection is not anticipated
given the lack of upper support. Probabilistic guidance currently
shows a decent signal (40 to 70%) for receiving 0.5" or rain over
central Wisconsin through Monday night. Accompanying the heat and
humidity during the latter part of the 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. 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 428 AM CDT Sat Jun 6 2026

Patchy fog, locally dense, will persist through this morning, with
vsby reductions down to IFR possible. Have included in the TAFs
via PROB30 mention over the central Wisconsin terminals where fog
has been ongoing overnight. Fog should then lift a few hours
after sunrise, with vsbys significantly improving. Otherwise, fair
weather cu field with bases at around 5 to 6k ft is set to
develop later this morning, persisting into this evening as
daytime instability wanes. Winds will start out of the northwest
at around 5 knots, shifting to easterly this evening. Exception
will be near MTW, where a southeast lake breeze develops during
the afternoon.

&&

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

&&

$$

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