textproduct: Green Bay

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.