Marine Weather and Tide Forecast for Suamico, WI

DISCUSSION
Issued at 432 AM CDT Wed Apr 23 2025

Clear to partly cloudy skies prevailed across the forecast area early this morning. The expected fog has been slow to form thus far, but suspect patchy fog will develop toward sunrise. Dry conditions held across GRB CWA, but a small cluster of storms with pea to nickel size hail was ongoing across Upper Michigan (ahead of a weak short-wave), and showers and storms had developed in a more moist and unstable air mass from Iowa into N IL.

Precipitation Chances: A cold front (currently over NW MN) will approach the region today, and edge into NC WI later in the afternoon. Ahead of the front, moisture will increase, with PWATs rising to around an inch in the Fox Valley/lakeshore areas during the afternoon. In addition, modest instability (CAPE of 300-800 j/kg and mid-level lapse rates of 7-7.5 C/km) will build ahead of the front, resulting in a gradual increase in showers and scattered thunderstorms during the afternoon. Deep layer shear is strong (45-65 knots), so isolated strong storms could form if enough heating occurs. SPC SREF 40+ dBZ paintballs show the best concentration of storms occurring south of a line from ISW-SUE between 2-7 pm, and a few models suggest a weak boundary (perhaps a warm front) lifting into the Fox Valley during this period. SPC has outlooked our far southeast counties in a Marginal Risk for large hail, and this looks reasonable. The showers and storms will linger across the southeast part of the forecast area into the evening, and weak instability/high PWATs lingering over our southern counties will support a small chance of showers and storms there into early Thursday morning.

The precipitation forecast is tricky for Thursday and Thursday evening, as high pressure may tend to suppress shower activity in far northern and eastern WI. However, several models develop a narrow frontogenetic band of showers somewhere over northern WI during the morning, with a gradual expansion of showers near this feature in the afternoon and evening. Have focused the highest pops over areas well northwest of the Fox Valley through the evening, but confidence was not high enough to forecast a completely dry forecast for GRB at this time. Model consensus continues to show the best potential for widespread significant rainfall occurring late Thursday night into Friday morning as WAA, a short-wave trough and 850 mb frontogenesis move through and low pressure tracks across N IL or S WI. We should see a diminishing trend in the precipitation Friday afternoon with dry conditions returning Friday evening and lasting through most of the weekend as a large high pressure system builds into the western Great Lakes.

A strong low pressure system is expected to lift northwest of the region early next week, and drag a cold front through WI on Tuesday. The chance of showers and thunderstorms will increase as the front approaches, and the pattern suggests potential for severe thunderstorms during the Monday afternoon through Tuesday period.

Gusty Winds Friday into Friday Night: Winds will be light to moderate through Thursday. The pressure gradient will increase between high pressure over Canada and low pressure tracking S/SE of the forecast area Friday into Friday night. Gusts to 25 to 35 mph can be expected, with the highest gusts occurring in the Fox Valley and lakeshore areas Friday afternoon and evening.

Temperatures: A warming trend is expected today, with highs reaching into the middle 60s to around 70. A modest drop in temperatures is expected after the cold front moves through tonight, and even more cooling is expected as widespread rain moves through Thursday night into Friday. This should cause temperatures to drop a little below normal by Friday. Partly cloudy skies will help boost readings back above normal over the weekend, with gusty S-SW winds ahead of a cold front pushing temperatures much above normal early next week.

AVIATION
for 18Z TAF Issuance Issued at 112 PM CDT Wed Apr 23 2025

An area of showers and thunderstorms moved through the east-central WI TAF sites this morning and will continue to exit northeast early this afternoon. Clouds have decreased across all TAF sites early this afternoon, however, SCT high clouds to the west are expected to continue spreading eastward through the afternoon.
Additionally, a SCT cu field is developing in portions of central WI, which may spread into the central WI TAF sites this afternoon.
There is a large amount of uncertainty in the potential for the redevelopment of showers or thunderstorms later this afternoon into early this evening before the arrival of a cold front late this evening. Given the latest guidance and trends, have opted to not include the mention of thunderstorms at any TAF sites. A wind shift from SW to N/NW is expected to occur with the cold frontal passage late this evening/tonight. Patchy fog may also develop prior to the cold frontal passage across the east-central WI TAF sites.

KGRB/KATW...Despite the latest guidance decreasing the potential for the redevelopment of showers or thunderstorms later this afternoon into the early evening, decided to include a PROB30 for -SHRA from 01-05z Thu, as this appears to be the best window for redevelopment before the cold front arrives. Should showers or thunderstorms develop, anticipate a brief drop to MVFR vsbys.

GRB WATCHES/WARNINGS/ADVISORIES
None.