751
FXUS63 KGRB 290404
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
1104 PM CDT Sat Jun 28 2025

Updated aviation portion for 06Z TAF issuance

.KEY MESSAGES...

- Strong or severe storms are possible overnight, with strong wind
  gusts the main risk across north-central and central WI. The
  storms are expected to weaken as they move into northeast
  Wisconsin late tonight.

- A cold front is expected to move across the region Sunday
  afternoon and evening, bringing additional chances of
  thunderstorms. Some of these storms could become strong or
  severe with damaging winds and large hail.

- Thunderstorms could bring locally heavy rainfall to the
  area through Sunday night, with rainfall rates of 1 to 2
  inches per hour resulting in localized flooding especially
  in urban areas.

- Temperatures and humidity will trend back above average this
  weekend, with near to above average temps continuing into next
  week.

&&

.DISCUSSION...
Issued at 248 PM CDT Sat Jun 28 2025

Short Term...Tonight and Sunday

The complexities of summer forecasting are in full swing this
afternoon as there are many differing solutions in the evolution
of thunderstorm development tonight. Current expectations are
for thunderstorms to develop across Minnesota and move east-
southeast into Wisconsin during the late evening and overnight
hours. The greatest risk of thunderstorms will be across north-
central and central Wisconsin as the models have the storms
weakening, and in some cases dissipating by the time they reach
northeast Wisconsin towards 12z. Bufkit soundings indicated
strong winds over 40 knots in the low levels on the Rhinelander
sites through 3 am Sunday, which the storms could tap. The GFS
sounding also indicated as least 1,000-2,000 J/KG and wet bulb
zero heights around 11,000 feet to support hail. Locally heavy
rainfall should also be expected. Lows tonight should fall into
the 60s.

On Sunday, the evolution of the overnight convection along with
outflow boundaries will impact the amount of heating during the
day. Some of the models have the early morning convection decaying
while other meso models lingered scattered showers and storms
through the morning. The cloud cover and rain could impact high
temperatures which will be in the 80s to lower 90s, warmest
readings across east-central WI where heat indices will reach
the middle to upper 90s. The threshold for a Heat Advisory is
100F. A cold front will move across the area Sunday afternoon
and evening, bringing an increased risk of severe storms. The
Storm Prediction Center Day 2 Outlook has much of the area in
a Slight Risk. Bufkit soundings off the GFS were showing
2,000 to 4,000 J/KG of CAPE although shear values were not
too impressive around 20 knots. Damaging winds is the main
risk, although some large hail can`t be ruled out.

Long Term...Sunday Night Through Saturday

Next week... Decaying low pressure and coincident trough will
bring our next chances for showers/storms, mostly diurnal in
nature, Monday morning and afternoon. Isolated storms will be
possible as modest instability and steep lapse rates build out
ahead of the cold front, although deeper moisture will struggle to
make it up into Wisconsin as high pressure builds over the
northern Plains. When paired with early morning FROPA and
subsidence behind the front, this should help keep storm coverage
at bay during the afternoon. This being said, a strong or severe
storm would not be out of the question Monday afternoon due to
favorable synoptic setup and sufficient deep-layer shear.
Inverted-V soundings and elongated hodographs would support gusty
winds and hail as the primary threats. Northwest flow regime then
sets up along the leading periphery of an upper-level ridge,
bringing a brief reprieve from wet weather to much of the Great
Lakes through mid-week. Some ridge rider activity then looks to
be possible toward the end of the week, although predictability
within the longwave flow regime remains challenging. Result ends
up being low-end PoPs with slight chance thunder during the
Thursday/Friday timeframe, although this is wont to change
throughout the week. Otherwise, steady-state temperatures in the
upper 70s and 80s prevail through the end of the work week,
ushering in a period of seasonable summer weather. Any deviation
to above/below average will likely hinge on frontal timing and
location, as well as cloud cover.

&&

.AVIATION...for 06Z TAF Issuance
Issued at 1103 PM CDT Sat Jun 28 2025

Prevailing conditions will remain VFR through Sunday. The main
concern will be the potential for periods of showers and storms
moving across the state at times. The first round is expected to
push into central and north-central WI after 06z. There is a
potential for gusty winds and heavy rain with these storms. Though
a lower risk, some of the storms could reach the Fox Valley and
far northeast WI after 10z so have continued to include PROB30 to
cover this. Some fog may form CWA/AUW/RHI in wake of the overnight
storms.

There may be a break in showers and storms for the rest of the
morning, though there are now indications more showers and storms
could develop, especially over the north. The approach of a cold
front and building instability will then result in another round
of scattered strong to severe storms mid to late afternoon. These
storms could produce strong wind gusts. Have included a mention for
storms in all TAF sites except MTW. Brief MVFR conditions will be
possible during these storms. Showers will linger in wake of the
storms into the evening as the cold front crosses the area.

&&

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

&&

$$

DISCUSSION.....Eckberg/Goodin
AVIATION.......JLA