436
FXUS63 KGRB 032340
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
640 PM CDT Thu Jul 3 2025

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Continued potential for showers and thunderstorms late tonight
  into Friday (July 4th). Marginal chance for severe weather
  tonight.

- Better chance for widespread rain and storms will occur Saturday
  and Saturday night. There is marginal chance for severe and the potential
  for heavy rainfall Saturday into Saturday night.

- Temperatures will be above normal through the holiday weekend,
  with very warm and humid conditions expected Friday (July 4th)
  and Saturday.

&&

.DISCUSSION...
Issued at 149 PM CDT Thu Jul 3 2025

Rain late tonight into Friday...
The weak frontal zone remains visible on satellite this afternoon
as an area of cumulus stretching from southwest Wisconsin to the
western portions of the state. As warm air advection kicks up
again late this afternoon and evening, this boundary will once
again lift into the region for the early overnight period.
Elevated showers and thunderstorms are then expected to develop
again, pushing into central Wisconsin from the southwest. Best
timing still remains from the overnight period around midnight
through the mid to late morning hours on Friday. Would expect the
best convective potential to be earlier in the overnight period,
with just some weaker storms or even just showers around by the
early morning period. Severe weather potential remains fairly
marginal, with relatively little instability and shear in the
region, but some brief wind gusts and small hail will be possible.
Any remaining convection will then slowly be suppressed through
the afternoon on Friday as ridging works its way into the region.
Maintained low pops further east as the ridging arrives, as some
meso models do allow for weak instability late in the day.
Regardless, mostly dry conditions are expected by firework time in
the early overnight.

Saturday...
The best chance for widespread rain and showers arrives on
Saturday as a cold front sweeps across the region from west to
east. Models have largely kept the slower arrival time, bringing
the front through mainly in the afternoon to evening period of
Saturday. As a result, 1-2 thousand J/kg CAPE will have a chance
to develop ahead of the front before storms arrive. Shear still
looks weaker but sufficient, around 20-30 knots, so some stronger
or a few severe storms will remain in the forecast. SPC currently
has most of northeast Wisconsin in the Marginal risk category for
severe weather, which makes sense. In addition to any severe
weather, ample moisture in the region will support a heavy rain
threat, with many areas seeing at least 40-60% of exceeding half
an inch of rain with the storms.

Rest of the Forecast...
Drier conditions then return behind the cold front Saturday, as
high pressure returns through early next week. The next hints of
some unsettled weather are not in the forecast until we get
towards the middle of next week.

Temperatures...
Above normal temperatures are expected through Saturday, followed
by near to a little below normal conditions through the middle of
next week. Very warm and muggy conditions arrive for Friday (July
4th) and linger over eastern WI into Saturday, with heat indices
into the lower to middle 90s. The heat and humidity will impact
outdoor activities for the 4th of July, but heat indices fall a
little short of advisory criteria at this point.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 631 PM CDT Thu Jul 3 2025

Isolated thunderstorms extended from just east of Wisconsin
Rapids to near Wautoma to Red Granite early this evening.
This cluster of storms could produce wind gusts to 35 knots
and small hail at KY50 until 02z. Otherwise, additional
thunderstorms are expected to develop alter this evening
and overnight. These storms are expected to develop around
or a few hours after 06z at KAUW/KCWA. Highest confidence
in storms are across central WI as models differ on timing
and eastward extent of the storms into the morning of 4th
of July. For the other TAF sites, went with a PROB30 group
due to the uncertainty in the amount of storms during this
time frame. Hot and increasingly humid conditions expected
for the 4th of July. Along with the heat and humidity, hazy
condiitons may develop at times.

&&

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

&&

$$

DISCUSSION.....Uhlmann
AVIATION.......Eckberg