445
FXUS63 KGRB 110827
AFDGRB

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

Forecast discussion for routine morning forecast 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 06Z TAF Issuance
Issued at 1058 PM CDT Thu Jul 10 2025

Showers from the evening will give way to clearing skies and some
fog over central WI overnight. Also could see patchy fog over
north-central WI. Have continued to carry MVFR VSBY with TEMPO
groups for IFR VSBY at AUW/CWA and RHI. Though fog will lift
around daybreak, IFR stratus could linger into mid morning.
Over east-central WI, no fog is expected, but a small chance of
some showers may arrive after 07-08z as steadier showers over
southern WI graze the area while lifting across south half of Lake
Michigan. The showers will be done shortly after daybreak. In
wake of any showers, expect MVFR CIGS to prevail much of the day
as easterly flow keeps stratus persistent, except over far north-
central WI with only scattered to broken mid and high clouds are
expected.

Based on recent model trends for Friday, have refreshed TAFs to
keep all sites dry through early afternoon. Did intro PROB30 for
some thunderstorms over central WI terminals (AUW/CWA) late in the
day as next wave arrives with increasing instability. By Friday
evening, most of the area will see scattered showers with small
chance of thunder. Conditions on Friday evening will mainly be
VFR central WI to north-central WI, while MVFR will grudgingly
hold over east-central WI sites (GRB/ATW/MTW).

&&

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

&&

$$

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