Green Bay, Wisconsin 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

667
FXUS63 KGRB 251920
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
220 PM CDT Fri Jul 25 2025

Forecast discussion for routine afternoon forecast issuance

.KEY MESSAGES...

- 30-50% chance for thunderstorms Sunday night into Monday. Any
storms could be strong to severe.

- Turning hot and humid again Sunday and Monday. Heat Advisories may
eventually be needed with potential for heat indices  exceeding 100
degrees.

&&

.DISCUSSION...
Issued at 219 PM CDT Fri Jul 25 2025

Short Term...Tonight and Saturday

Zonal, confluent midlevel flow over the upper Great Lakes is
promoting surface high pressure today. This is leading to tranquil
conditions with some fair weather cu. Also, wildfire smoke from
Canada continues to stream into the area, resulting in vsby reduced
to around 5 miles in some spots. The high will continue shifting
east of the area tonight into Saturday, setting up modest return
flow, and allowing smoke to advect out of the area by Saturday. This
should lead to a boost in the high temps by a couple degrees
relative to Friday, with highs mainly in the mid-80s and heat
indices 85-90. A loosely organized corridor of vorticity maxima,
coincident with an east-west-oriented plume of anomalous PWAT
values, will remain to our south on Saturday. This will continue the
drier trend for the majority of our area on Saturday, although a
shower or two along the northern fringe of the moisture corridor
can`t be ruled out over the southern tier of counties in the CWA.

Long Term...Saturday Night Through Friday

Main forecast issues are potential for high heat indices Sun-Mon and
convective potential Sunday night into Monday. A large midlevel
anticyclone will be located across much of the southern US Sunday,
and will expand northward a bit on Monday. Meanwhile, southwesterly
flow at 850 mb will strengthen modestly, advecting a warmer airmass
into the Great Lakes from the central Plains. NAEFS mean 850 mb
temps Sun/Mon are in the lower 20s (C) over the forecast area, which
is +1 to +2 sigma even for late July, and are near the daily maximum
on the SPC sounding climo. NBM high temps are in the upper 80s
(north) to lower 90s (south), and lower 70s dewpoints look to remain
over roughly the southern half of the CWA, where there is a
possibility of heat advisory criteria (100F heat indices). Monday
could be even a couple degrees warmer with the high dewpoints
remaining (although they may mix out into the upper 60s north).
However, there is a bit more uncertainty with convection and cloud
cover.

Thunderstorm chances appear nearly nil during the daytime Sunday as
forcing for ascent remains far upstream and forecast soundings
suggest significant capping. Sunday night into Monday, there is
fairly good confidence in one or more convective complexes
developing within extreme instability over northern Minnesota as it
is overspread by a belt of faster 500 mb flow and a shortwave
trough. There is considerable uncertainty in the track of any such
convective complex, but given the high theta-e airmass overspread by
steeper midlevel lapse rates from the west, any MCS propagating into
NE WI would carry some severe risk.

Tuesday onward, the ridge expands into the northern Rockies, while
the northern extent of it is flattened by lower heights approaching
south-central Canada and the upper Great Lakes. That should spell a
return to a more seasonable airmass as high pressure sets up over
the northern Plains and funnels cooler air in from the north. A few
more showers or storms can`t be ruled out Tuesday with the low-level
front still in the vicinity, with consensus supporting a drier end
to the week.

&&

.AVIATION...for 18Z TAF Issuance
Issued at 1234 PM CDT Fri Jul 25 2025

SCT MVFR cumulus field has developed early this afternoon as pesky
low stratus from this morning continues to erode with daytime
heating. However, biggest impact to aviation will be near-surface
wildfire smoke pivoting across the eastern half of the state this
afternoon. Vsbys have degraded to around 6 SM across the eastern
TAF sites, and will continue to do so throughout the afternoon.
Impacts from smoke will take a little longer to make it to AUW and
CWA, though should get there late this afternoon. Smoky/hazy
conditions could linger until as late as the end of the TAF period
(18Z Saturday). Tried to provide resolution where possible,
including timing of thickest smoke.

.OSH... SCT daytime cu field with bases at around 2 to 3k ft are
encroaching on OSH early this afternoon. Near-surface smoke plume
has resulted in vsbys dropping to around 6 SM, which are expected
to further degrade (4 to 5 SM) throughout the afternoon. Otherwise,
winds to be predominantly out of the east at around 5 knots,
veering south Saturday morning. Slight chance precip (15 to 20%)
arrives late Saturday morning from remnant MCV activity currently
out over Kansas and Missouri, though have not included in the OSH
TAF due to low confidence.

&&

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

&&

$$

DISCUSSION..... WFO MQT
AVIATION.......Goodin