306
FXUS63 KGRB 080247
AFDGRB

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

Updated aviation portion for 06Z 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 06Z TAF Issuance
Issued at 946 PM CDT Mon Jul 7 2025

VFR conditions will continue this late evening, then isolated to
scattered showers and isolated storms with VFR/MVFR (possibly
briefly IFR at times) ceilings/vsby are forecast to arrive from
west to east after midnight. Continued the TEMPO groups for storms
across central and north central WI, where thunder chances are
highest, but storm coverage looks to be rather small. Went with
PROB30 for locations over the east. After the initial area of
showers and isolated storms moves through, isolated showers or
storms will be possible the rest of the afternoon and evening on
Tuesday with MVFR/VFR ceilings. Included PROB30s for this threat.

Winds will remain light out of the south/southeast overnight.
Winds will shift to the west/northwest on Tuesday, but remain
mainly under 10 kts.

&&

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

&&

$$

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