Marine Weather and Tide Forecast for Suamico, WI

DISCUSSION
Issued at 347 AM CDT Sat Jun 21 2025

Severe Weather Potential This Morning...
Clusters of storms tied to warm air advection on edge of very unstable airmass and within 50kt of effective shear have produced occasional large hail from north-central to far northeast WI. This activity will continue to shift east-northeast. Attention is on southern portion of bow echo MCS that produced wind gusts upwards of 90 kt earlier tonight into western MN. As the bow pushed into stabilizing flow off Lake Superior, it has become weaker. However, tracking the feature to the east-southeast it will interact with much greater instability as it pushes into at least north-central WI this morning, arriving after 5 am. Will have to see if this intensifies again or mainly stays sub-severe. 0-1km shear is not alligned favorably with the line and DLH radar points to outflow outpacing the main line, so that could be a negative factor in getting damaging winds to the sfc from here on out as the environment is generally elevated. These storms will shift east out of the area after 8 am this morning. Tail of the complex may kick of few isolated additional storms through midday, so hung onto slight chances through that time.

Dangerous Heat Through Monday...

After storms exit today, heat and humidity this weekend will be the primary focus. Boundaries left over from storms this morning could impact how high temps temps get today, especially over the north. As has looked like for many days now, highs this afternoon and Sunday afternoon will reach the lower to middle 90s and with dewpoints in the lower 70s, heat index values will push into the 95 to 105 range. The peak of the heat will occur on Sunday for the entire area, firmly beneath upper ridge and dome of hot air aloft.
Nighttime lows tonight and Sunday night dropping into the mid to upper 70s (even near 80 in some locations across the Fox Valley to the lakeshore) will provide no relief to the heat. Heat Advisories continue with no changes. Eventually, could see Door County added for Sunday potentially and the end of the advisory to be trimmed over the north on Monday as cold front and convection chances keep max heat index values lower there. Given the active weather ongoing this morning, will let later shifts make that call.

It will be quite breezy today as southwesterly winds increase to 30 to 40 mph. Kind of atypical to see these strong winds with the heat and humidity, but looking upstream, dewpoints in at least the lower 70s do make sense.

Active Weather Continues Next Week...

Ridge centered across the Ohio Valley into the eastern Great Lakes early in the week will flatten over the course of the week.
This will result in a trend towards cooler, more seasonable conditions locally across the area with time. No change in previous thinking with NAEFS showing a signal for precipitable water values over the 90th percentile relative to climo across parts of the Upper Midwest for much of next week on the periphery of the ridge. Deterministic models show the potential for heavy rain as main sfc front is stalled across the area. Surface boundary placement, timing/location of shortwave troughs and extent of instability will impact where more organized heavy rain/severe weather potential may exist.

Monday still looks to the be the greatest risk for severe storms as the cold front crashes into the heat and humidity. Still some concern that stronger shear lags the front and MLCAPEs of 1000-2000J/kg. At the least would be pulse type storms, but certainly risk of more organized type activity. SPC has most of area in a Slight Risk.

AVIATION
for 12Z TAF Issuance Issued at 648 AM CDT Sat Jun 21 2025

Showers and storms will cross northern WI, including RHI, through mid morning. Otherwise, mix of MVFR and VFR clouds will give way to scattered to broken mid clouds later today. Skies will be mainly clear tonight. Low-level jet to 40 kts overhead results in low- level wind shear through mid morning. Southerly winds will increase today, with gusts up to 35 kts during peak mixing of the afternoon.
South winds will remain gusty tonight, with gusts 20-25 kts most of the night.

GRB WATCHES/WARNINGS/ADVISORIES
Heat Advisory from noon today to 7 PM CDT Monday for WIZ005- 010>013-018>021-030-031-035>040-045-048>050-073-074.

Beach Hazards Statement through Monday evening for WIZ022-040- 050.