927
FXUS63 KGRB 041130
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
630 AM CDT Tue Aug 4 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- A cold front will bring chances for scattered showers and storms
  through this evening. The severe threat remains low. Isolated
  showers may continue into Wednesday.

- Elevated wildfire smoke may become near surface at times today
  and tonight. Moderate (yellow category) air quality readings are
  forecast during this time.

- Warmer and more humid conditions build into the area over the
  weekend, along with periodic chances for showers and storms
  Friday through Sunday.

&&

.DISCUSSION...
Issued at 1214 AM CDT Tue Aug 4 2026

Rain/storm chances... Latest surface obs show a cold front
associated with a broken line of showers/storms draped over
eastern Minnesota as of early this morning. Front will continue to
impinge on northwest Wisconsin over the next couple of hours,
though shower activity should become more scattered upon reaching
the forecast area mid-morning. Robust capping and remnant dry air
to around 800 mb from departing high pressure should keep showers
mostly isolated through early this afternoon, before CAMs show
re-development occurring along the front during peak heating as
the cap erodes. Though the severe threat is low, skinny CAPE
profiles (1,000 to 1,200 J/kg) and near inverted-V profiles would
suggest gusty winds as a potential hazard with any storms as
daytime mixing taps into 25 to 30 knot winds at the top of the dry
layer.

Convergence along the front ramps up across southern Wisconsin
early this evening as PWATs in proximity to the surface low
increase to near 2". As such, most recent suite of model runs
retains the axis of heaviest precip off to our south, with NBM
probabilistic guidance only showing a 20 to 40% signal for
receiving 1" of rainfall localized to east-central Wisconsin.
Light shower activity may continue into Wednesday as the low
tracks over southern Michigan and cyclonic flow lingers, though
most areas should remain dry.

Late week rain/storm chances... As the synoptic pattern de-
amplifies and zonal flow establishes itself across the CONUS mid-
week, expect a brief dry period through Thursday. Flattened upper
trough and attendant surface low then approach the Midwest on
Friday, bringing our next widespread shower/storm chances that
last through the weekend. Predictability in storm coverage and
intensity remains low this far out, as these will likely hinge on
how western ridge evolves throughout the week and how much
associated heat/humidity we can get into our neck of the woods.
Cursory glance at ML guidance paints a broad swath of 5 to 15%
probs over the upper Mississippi Valley for Days 5 and 6, though
this will continue to be monitored in the coming days.

Smoke... As post-FROPA winds shift to the west later this
morning, shower activity along the front may help mix elevated
smoke plume down to the surface at times through this evening. No
significant reductions in visibility are expected, though air
quality may degrade to moderate (yellow category).

&&

.AVIATION...for 12Z TAF Issuance
Issued at 450 AM CDT Tue Aug 4 2026

Clouds will continue to lower and thicken along the cold front
throughout the morning, bringing MVFR cigs to the central and
north-central TAF sites by around 14Z. Though coverage is progged
to diminish upon approaching the forecast area, FEW to SCT
showers are expected to linger in/near AUW, CWA, and RHI through
around 18Z. Have thus opted to include TEMPO groups for -SHRA
accordingly. Re-development of showers/storms will then be
possible this afternoon mainly across east-central Wisconsin,
though confidence in storm coverage is low. Have nevertheless
included PROB30 mention of -TSRA for GRB, ATW, and MTW for when
thunder is most likely this evening. Cigs will likely remain low-
end VFR during this time.

LLWS may linger across central and north-central Wisconsin for
the next couple of hours as 850 mb jet tracks northeast. Winds
then increase ahead of the front this afternoon, gusting to 20
knots at all terminals. Winds decrease and veer to the west by
this evening.

&&

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

$$

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

NWS GRB Office Area Forecast Discussion