NWS-Green Bay Forecast Discussion

						FXUS63 KGRB 261035
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
535 AM CDT Tue May 26 2026

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Hot record to near-record temperatures expected this afternoon,
  with highs in the upper 80s to lower 90s.

- 50 to 70% chance for showers and thunderstorms this afternoon
  and this evening across central and east-central Wisconsin, with
  some strong to marginally severe storms possible with large
  hail and strong winds.

- Isolated thunderstorms are possible Wednesday afternoon across
  central Wisconsin. A few storms could become strong to severe
  with large hail and damaging winds.

- Above normal temperatures are expected through early next week,
  with highs forecast mainly in the upper 70s and 80s.

&&

.DISCUSSION...
Issued at 110 AM CDT Tue May 26 2026

A cold front, currently situated across the northern Great Lakes,
will slowly sink south into northern Wisconsin this afternoon,
central Wisconsin tonight, then through southern Wisconsin on
Wednesday.

Ahead of the cold front a very warm airmass will be in place as
high temperatures today soar into the upper 80s to the lower 90s,
with the highest temperatures just west of the Fox Valley. These
hot temperatures will reach record to near-record values as many
locations records are around 90 degrees. Despite the hot
temperatures expected, dew points will only be around 60 degrees
which will keep heat index values manageable.

The warm temperatures will allow instability to build across the
region this afternoon, as SBCAPEs rise to 1500 to 3000 J/kg.
Despite the abundant instability, effective shear is only expected
to be 10 to 20 knots with a fairly weak wind field aloft. Forcing
is not all that impressive in the middle and upper levels, with
the main lifting mechanism expected to be the fairly shallow back
door cold front expected to slowly sink south through the evening.
That being said, model soundings do show an inverted-V in the
lowest levels of the atmosphere with DCAPE values around 1000
J/kg, which is conducive for downbursts, as well as decent CAPE
profiles in the hail growth zone. This points to marginal pulse
severe storms later this afternoon into early this evening when
instability is maximized across the region.

Precipitation chances will fall off precipitously as the evening
wears on as the front sinks south and instability wanes. Dry
weather is then expected through Wednesday morning with additional
chances for showers and thunderstorms (20-30% chance) Wednesday
afternoon across central Wisconsin as a weak shortwave tracks
through the western Great Lakes. There will be a reservoir of
1000-2000 J/kg of SBCAPE as this shortwave tracks through central
Wisconsin with a bit better bulk shear values around 30 knots.
Although storms will be more isolated in coverage, any storms that
develop could be marginally severe storms given the better shear
and still decent instability.

High pressure then settles in across the region later this week,
which is expected to keep the region dry through the upcoming
weekend and even through the early part of next week.

After the hot temperatures expected today, temperatures will fall
a bit but still remain above normal for the rest of the week and
into the early part of next week.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 535 AM CDT Tue May 26 2026

A cold front will sag south across the area today, with scattered
showers and thunderstorms developing during the mid to late
afternoon, and continuing across central and east-central
Wisconsin through the evening. Kept the TEMPO groups for mostly
likely 4-hour period for thunderstorms for the TAF sites. Dry
weather is then expected overnight.

South to southwest winds will gust to around 15 kts at times
today, but will turn northeast in the wake of the frontal passage
this afternoon/evening. Light winds below 10 kts are then expected
overnight. KGRB VWP indicates some LLWS is present across east-
central Wisconsin, but should mix out shortly after TAF issuance.

&&

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

&&

$$

DISCUSSION.....Kurimski
AVIATION.......Kurimski