363
FXUS63 KGRB 111131
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
631 AM CDT Fri Jul 11 2025

Updated aviation portion for 12Z TAF issuance

.KEY MESSAGES...

- Showers and thunderstorms will be possible at times this
  afternoon. Heavy downpours and gusty winds will be possible
  with any storm activity.

- A few strong to severe storms will be possible on Saturday.
  Gusty winds and isolated large hail will be the main hazards
  with any stronger storms.

- Next round of active weather arrives during the middle of next week.

&&

.DISCUSSION...
Issued at 325 AM CDT Fri Jul 11 2025

Mesoanalysis and convective trends... Isolated showers associated
with remnant MCV activity continue to percolate over central and
east-central Wisconsin early this morning as 700 mb vort max
tracks over the Great Lakes. The brunt of the action will remain
off to our south, however, as showers and storms ride a modest
low-level jet. Dissipating showers later this morning are then
likely to leave overcast skies and drier conditions in their wake.

This afternoon/evening... Southerly track persists for heavy
rain/severe weather potential today given disjoint between
driving shortwave axis and timing/location of weaker feature
coming out of the Intermountain West. This has resulted in a lower
confidence forecast regarding storm coverage and intensity this
afternoon, and therefore heavy rain potential as CAMs suggest
better dynamics being locked up to our south along pre-existing
outflow. This being said, would not be surprised to see a storm or
two fire off in central Wisconsin this afternoon as modest
instability builds out ahead of an approaching cold front. Though
severe storms are no longer expected, a low-end wind threat would
be supported by inverted-V soundings. Moreover, main swath of
precip may still nick east-central Wisconsin this afternoon/evening
given combination of favorably moist atmosphere (PWATs
approaching 2", or ~175% of normal relative to climo) and more
southerly track. Warm cloud processes will be dominant during this
time as well, with cloud depths exceeding 12k ft. Realistic
scenario would be additional rainfall amounts of around 1 to 1.5"
were this to pan out. Due to uncertainty in this outcome, have
opted to keep QPF on the lower end, with signals for convective
precip out over central Wisconsin where thunder is most likely.

Saturday... Better chances for strong/severe storms Saturday
afternoon will be tied to upper-level trough and attendant cold
front as they traverse the Great Lakes. Driving trough begins to
take on an increasingly negative tilt as it ejects across the
upper Mississippi Valley, increasing mid-level flow out of the
southwest and raising surface dewpoints into the upper 60s to low
70s. Narrow corridor of 1,000 to 2,000 J/kg MUCAPE thus develops
along the leading edge of the cold front early Saturday
afternoon, where convection is expected to initiate over central
and north-central Wisconsin. Gusty winds and isolated large hail
would be the primary concerns with any stronger storms.

Rest of the extended... Next chances for precip arrive sometime
mid-week as long-range guidance grabs onto a signal for a weak
boundary passing over the upper Midwest. More notable chances for
rain/storms then arrive end of week as more robust troughing digs
down from Canada. Models have yet to hone in on exact timing of
this feature.

&&

.AVIATION...for 12Z TAF Issuance
Issued at 628 AM CDT Fri Jul 11 2025

Similar to yesterday, remnant moisture from earlier showers
paired with light winds have allowed for patchy fog/low stratus
to develop early this morning, namely over the western TAF sites.
Given behavior of fog yesterday morning, will opt to briefly carry
over into the 12Z TAFs via reduced vsbys. Though fog is expected
to lift shortly after daybreak, MVFR to IFR stratus deck could
stick around through late morning. Will continue the trend of
keeping all sites dry until the afternoon.

Following a brief lull in activity during the morning,
isolated to scattered showers and storms arrive to central
Wisconsin early this afternoon, becoming more widespread into the
evening and dropping cigs down to MVFR/IFR. Will once again
include a TEMPO group for AUW and CWA where thunder seems most
likely.

&&

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

&&

$$

DISCUSSION.....Goodin
AVIATION.......Goodin