538
FXUS63 KGRB 072358
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
658 PM CDT Mon Jul 7 2025

Updated aviation portion for 00Z TAF issuance

.KEY MESSAGES...

- Seasonal summer weather is expected this week. Shower and
  thunderstorm chances expected late tonight through Tuesday
  evening, and Friday into Saturday. Heavy rainfall possible
  with the late week system.

&&

.DISCUSSION...
Issued at 238 PM CDT Mon Jul 7 2025

High pressure dominated our weather this afternoon, with SCT-BKN
stratocumulus, light winds and comfortable temperatures in the
70s.

Forecast concerns include shower/thunderstorm chances late tonight
through Tuesday evening, and again Friday into Saturday.

Precipitation Trends Late Tonight through Tuesday Evening...based
on the latest CAMs, will have the highest pops (Likely category)
impacting the forecast area late tonight through Tuesday morning.
The forcing during this period will be provided by the RRQ of a
weak jet streak, weak WAA and a modest influx of moisture (PWATs
1.2-1.7 inches) and elevated instability. Convection looks to be
more scattered during the afternoon and evening, as a short-wave
trough brushes through northern WI and a weak surface low/front
moves through. Daytime instability will be on the marginal side
(CAPE 800-1300 j/kg) due to extensive cloud cover, so the threat
of severe storms looks to be low.

Precipitation Trends Late Friday into Saturday... The late week
system appears to have a bit more dynamic forcing, with a
negatively-tilted short-wave moving through Friday afternoon and
night. In addition, PWATs will increase to around 2 inches in C/EC
WI, so at least locally heavy rainfall is expected. Current
probabilistic guidance is not too excited about heavy rainfall,
with only around a 10 percent chance of 1+ inches of rain. Suspect
these probabilities will come up a bit as we get closer to the
event. Have extended pops into Saturday, as an upper trough
crosses the region.

Seasonal temperatures are expected through next weekend, with
highs hovering a few degrees below to a few degrees above normal.

&&

.AVIATION...for 00Z TAF Issuance
Issued at 658 PM CDT Mon Jul 7 2025

VFR conditions will continue this evening with few/scattered
stratocumulus clouds in some spots, along with some high clouds
spreading over the region. An area of showers and embedded storms
is forecast to arrive at RHI/CWA/AUW by 08z-10z/Tue and
GRB/ATW/MTW by 11z-13z/Tue. Continued the TEMPO groups for
thunderstorms at each site, with the most favorable 4-hour time
period for occurrence. MVFR to possibly IFR ceilings/vsbys are
expected with the showers/storms. After the initial area of
showers and isolated storms moves through, isolated showers or
storms will be possible the rest of the afternoon with MVFR/VFR
ceilings. Included PROB30s for this threat.

Winds will remain light and variable early this evening, shifting
mainly to the south/southeast later tonight. Winds will shift to
the west/northwest on Tuesday, but remain mainly under 10 kts.

&&

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

&&

$$

DISCUSSION.....Kieckbusch
AVIATION.......Bersch