NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 041130
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 AM CDT Thu Jun 4 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Scattered showers/storms return today, lasting into the weekend.
  Limited potential for strong storms this afternoon, with better
  chances for strong or severe storms Friday afternoon.

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

&&

.DISCUSSION...
Issued at 1226 AM CDT Thu Jun 4 2026

Rain/storm chances... Convection in the vicinity of the frontal
boundary over western Minnesota continues to trek along early
this morning, though it should diminish within the next couple of
hours as it outruns better instability and encounters drier air.
Re-development of scattered showers/storms will then be possible
later this morning into early this afternoon as better moisture is
drawn north by high pressure shifting off to the east. Remain
somewhat critical for severe potential this afternoon as cloud
shield from aforementioned convection will hinder better
instability from building. Also seems to be somewhat of a disjoint
between upper forcing and deep layer shear, so any stronger
storms will hinge upon upstream development. As such, wind looks
to be the primary threat with any stronger storms, though any
severe threat would be little to none.

Better chances for any strong/severe storms comes Friday afternoon
and evening as driving shortwave treks over the northern Plains
and FROPA makes it into Wisconsin. Mid-level convergence and
increasing deep-layer shear (35 to 40 knots) would provide a
stronger base for convective activity, as abundant moisture
interacts with instability reservoir (1,500 to 2,000 J/kg) near
the surface low. However, greatest uncertainty will once again
revolve around cloud cover from sub-severe morning convection,
and whether or not sufficient destabilization will be able to
occur. This being said, lingering boundaries/outflow from said
convection may provide enough surface lift to get a couple of
stronger updrafts going later Friday afternoon. In this scenario,
steepening lapse rates and pseudo inverted-V profiles would
support gusts to 60 mph and up to 1" hail as the primary hazards.
Accompanying the severe threat on Friday will be the potential
for heavy rain as PWAT axis reaches around 1.5 to 1.75" (90th
percentile) and dewpoints climb into the mid 60s. Probabilistic
guidance continues to show a fairly widespread 40 to 70% chance,
locally higher, for receiving 0.5" of rain, with a 30 to 50%
signal for 1". Would lean more pessimistic toward the higher
totals, as these would be more likely with training and/or slow-
moving storms. As it appears now, storm motion looks to be fairly
progressive.

Temperatures... Temperatures will remain above average over the
course of the next week as synoptic flow eventually re-amplifies
and building heat ridge/Hudson Bay high set us up under southerly
flow regime. Highs this afternoon will read several degrees higher
than yesterday, peaking in the mid to upper 80s from the Fox
Valley and up into far northeast Wisconsin. However, dewpoints in
the mid to upper 50s should hold down the overall heat risk to a 1
out of 4. Potential for heat-related impacts then drastically
increases during the early to middle part of next week, with
probabilities for 90-degree highs sitting at around 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. Cursory glance indicates that a level 3 out of 4
(major) risk may be possible toward the end of next week, though
this is beyond the current forecast period.

Fire weather... Fire weather concerns will continue to diminish
with the arrival of scattered showers/storms later this morning
into this afternoon. A slower arrival of the rain may allow RHs to
dip down into the low to mid 30s across portions of far northeast
Wisconsin this afternoon, though critical thresholds are not
expected to be met.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 507 AM CDT Thu Jun 4 2026

VFR conditions prevail through this afternoon, before BKN to OVC
MVFR cigs arrive later this evening. SCT showers and embedded
storms will precede the lower cigs early this afternoon, falling
from a mid cloud deck. Showers should arrive to the western sites
by around 20Z, diminishing in coverage by the time they reach the
eastern sites by around 06Z Friday. Have opted to include a
PROB30 mention for -TSRA in the RHI, AUW, and CWA TAFs where
thunder appears most likely. Attempted to provide further timing
resolution for shower arrival via PROB30 groups for all sites. Any
showers or storms that pass over a terminal may briefly reduce
vsbys to MVFR. Otherwise, winds increase out of the southwest this
afternoon, gusting between 15 and 20 knots.

&&

.GRB WATCHES/WARNINGS/ADVISORIES...
Beach Hazards Statement from 2 PM CDT this afternoon through
late tonight for WIZ022-040-050.
&&

$$

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