textproduct: Green Bay

KEY MESSAGES

- Scattered non-severe storms this afternoon and early evening, mainly across northeast Wisconsin.

- Next more widespread rainfall potential (70-90% chance) late Tuesday and Wednesday, but severe weather is unlikely.

- Near to below normal temperatures and comfortable humidity will prevail through next week.

DISCUSSION

Issued at 1215 PM CDT Sat Jun 20 2026

Tonight-Sunday: Scattered showers/storms this afternoon

A weak mid-level trough embedded in northwest flow aloft will swing across the Upper Great Lakes this afternoon. With steep low level lapse rates beneath cool mid-level temps, isolated to scattered showers/storms will develop, with the greatest focus across far northeast Wisconsin. These will quickly diminish after sunset. With limited instability (MLCAPE < 500 J/kg), the threat for severe weather is quite low. Lightning and brief downpours will be the primary hazards, although with the cool thermal profiles, very small hail cannot be ruled out with any stronger cores.

Patchy fog may develop overnight with weak boundary layer flow and clearing skies, but widespread dense fog is not anticipated.

Sunday continues to trend dry with precipitation associated with a shortwave trough and surface low expected to remain mainly south of the area. However, although instability is even weaker than today, an isolated shower could not be ruled out across northern Wisconsin during the afternoon, but chances are less than 20 percent.

Monday-Saturday: Cool, highest rain chances mid-week

A northwest flow pattern will persist across the region this week into the coming weekend. This flow pattern will keep temperatures and humidity levels relatively low for late June with highs mainly in the 60s and 70s.

The highest rain chances (70-90%) over the coming week right now are forecast to be late Tuesday into Wednesday as a trough of low pressure passes across the Great Lakes. With the relatively dry, cool airmass, significant destabilization appears unlikely, keeping the risk of severe weather low. The risk of excessive rain also looks low, given the limited instability, but there are at least low to medium (20-50%) chances for 1/2 inch of rain or more. Lower (30- 40%) chances for showers and storms persist into Thursday as cyclonic flow aloft and cool mid-level temps reside over the Great Lakes.

Beyond this time, confidence is lower with respect to pattern details and precipitation potential for late week. However, there are some indications that the belt of stronger mid-level flow (80th percentile 500 mb winds relative to climo), which will be focused south of the area across the central plains to Mid-Mississippi Valley for much of this week, may retreat northward in conjunction with greater moisture/instability towards the Upper Midwest and northern plains late next weekend into the following week, providing a more favorable environment for storms.

However, overall, for this time of year, at least over the next week, the risk for more impactful severe weather is low.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1215 PM CDT Sat Jun 20 2026

Thicker IFR/MVFR stratocumulus will scatter with rising ceilings early this afternoon back to VFR. Isolated to scattered showers/storms will develop this afternoon, with the higher chances for rain across far northeast Wisconsin, where thunder probabilities are 30-40 percent. Chances for thunder at area TAF sites are generally only 15-30 percent, so did not include any thunder mention for this issuance.

With light winds overnight, patchy fog may develop for a few hours around sunrise on Sunday, especially across northern Wisconsin. Otherwise, VFR conditions will persist through the period with winds becoming light this evening.

GRB WATCHES/WARNINGS/ADVISORIES

WI...None. MARINE...None.