691
FXUS63 KGRB 012337
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
637 PM CDT Tue Sep 1 2026

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Warm and humid conditions continue for the remainder of today
  with highs reading in the upper 80s to low 90s.

- Scattered strong/severe storms possible late tonight into
  Wednesday morning over portions of central to east-central
  Wisconsin. Main threats with any stronger storms will be
  damaging winds and up to 1" hail.

- Above normal temperatures and periodic rain/storm chances will
  continue into the weekend.

&&

.DISCUSSION...
Issued at 1048 AM CDT Tue Sep 1 2026

Meteorological fall is off to a warm start as early afternoon
temperatures have climbed solidly into the mid 80s, with dewpoint
readings in the low 70s in/around the Fox Valley. As such, heat
indices have risen into the upper 80s to low 90s across much of
east-central Wisconsin.

Storm chances tonight/Wednesday morning... Focus for the near-term
revolves around severe storm potential late tonight into early
Wednesday morning as shortwave energy and tandem front traverse
the Great Lakes. Storms should develop on the nose of a 40 to 45
knot LLJ over central Wisconsin between around 06 and 10Z
Wednesday, diminishing in coverage as they track further east
throughout the morning. Current thinking is that storms would
remain mostly elevated, though cannot rule out damaging wind
threat given 40+ knot wind at the top of the dry layer. Hail would
be a secondary threat given marginal lapse rates and skinny CAPE
profile. Locally heavy rain will be possible with storm activity,
though excessive rainfall potential should be held down due to
progressive storm motion. Greatest chance (40 to 50%) for
receiving 0.5" of QPF will be confined to central Wisconsin in
proximity to axis of higher PWATs.

Extended... Majority of the extended will be characterized by
periodic rain/storm chances and above normal temperatures as
warming ridge builds over the CONUS. However, storm
timing/predictability remains low thus far given the nature of the
synoptic pattern and model uncertainty surrounding retrograding
ridge. This will in turn affect potential cooldown heading into
next week, though signs point toward entering into a more
north/northwesterly flow regime.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 636 PM CDT Tue Sep 1 2026

A mix of a few VFR cumulus clouds and other mid and high clouds
will continue to spread across region through the late afternoon
and evening hours. Isolated to scattered showers and storms will
continue to develop and move east along/near a warm front
situated across southern MN/WI, slowly working into the area
overnight, mainly after 06z. A larger complex of showers and
storms may impact the area after 08-09z, but there is still come
uncertainty on just how large/intense this area will be or if it
will track far enough north to impact the TAF sites. Have used
TEMPO groups to highlight the greatest threat for storms at
AUW/CWA where chances for thunder are the highest, and PROB30
groups at GRB/ATW/MTW where chances are lower. Used a TEMP group
for shower chances at RHI overnight. The main threat from the
storms will be brief reductions in ceilings/visibilities, gusty
winds and torrential downpours.

Patchy ground fog will be possible overnight across far
northeast/east WI where clouds will be slowest to arrive and
dewpoints are the highest. Outside of gusty winds in/near any
storm, winds will remain under 10 kts.

&&

.FIRE WEATHER...
Issued at 1048 AM CDT Tue Sep 1 2026

Combination of dry air, subsidence/mixing from high pressure, and
warm temperatures may result in elevated fire weather conditions
developing over north-central Wisconsin later this afternoon. RHs
have already dipped down into the mid 30s across the sandy soil
regions in the far north, and should continue to decrease into
the low 30s and even upper 20s over the next several hours. Gusts
to 25 mph will be possible during this time. However, moisture
from prior rainfall should keep fuels from reaching critical
thresholds. Looking forward, extreme drought continues to expand
over portions of northwest Wisconsin, with little to no chances
for soaking rainfall currently in the forecast. Will continue to
monitor fire weather conditions throughout the month, especially
after we get our first frost/freeze.

&&

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

&&

$$

DISCUSSION.....Goodin
AVIATION.......Bersch
FIRE WEATHER...Goodin

NWS GRB Office Area Forecast Discussion