325
FXUS63 KGRB 111812
AFDGRB

Area Forecast Discussion
National Weather Service Green Bay WI
112 PM CDT Fri Jul 11 2025

Updated aviation portion for 18Z TAF issuance

.KEY MESSAGES...

- Showers and thunderstorms will be possible at times this
  afternoon into tonight. 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 18Z TAF Issuance
Issued at 110 PM CDT Fri Jul 11 2025

A mix of MVFR and VFR ceilings will continue this afternoon and
evening. A stray shower will possible this afternoon and early
evening across central and north central WI as daytime
instability builds. Otherwise, look for ceilings and vsbys to drop
later this evening and overnight (to IFR/MVFR) as a MCV spreads
showers/storms across much of the area. Still some disagreement
where the heaviest rain will fall (likely somewhere east of a
Stevens Point to Iron Mtn line), along with the best chance for a
storm, so have keep the storm chances in PROB30s for now. The
showers associated with the MCV will end early Saturday morning,
with isolated to scattered round of quick moving showers and
storms expected Saturday afternoon.

&&

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

&&

$$

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