Marine Weather and Tide Forecast for Marinette, WI

DISCUSSION
Issued at 116 PM CDT Sat May 9 2026

The latest RAP analysis and satellite/radar imagery show a deep upper trough centered from Hudson Bay to the central Great Lakes early this afternoon. Embedded shortwave energy is pushing a cold front across Lake Michigan with scattered light shower activity exiting to the east. Partial clearing is spreading across northwest Wisconsin and this clearing trend should continue east through the rest of the afternoon. Looking further upstream, a ridge of high pressure is positioned over the Plains and is gradually shifting eastward. Forecast concerns revolve around fire weather potential, frost potential, and light rain chances.

As skies clear this evening and winds become light under the influence of the approaching surface ridge, favorable radiational cooling conditions will develop. This will set the stage for frost development. While there is some concern that the pressure gradient may stay tight enough to keep temperatures up slightly, consensus guidance is insistent on lows in the middle 30s for areas west of the Fox Valley. Consequently, a Frost Advisory has been issued for much of central Wisconsin and west of Outagamie and Winnebago counties.

On Sunday, clouds will redevelop with the heat of the day.
Marginally unstable conditions off Lake Superior combined with weak shortwave impulses could lead to widely scattered light showers or sprinkles across far north- central and northeast Wisconsin Sunday afternoon, though amounts will be negligible.
Another round of frost appears likely Sunday night as high pressure settles directly over the state.

The next significant weather maker arrives on Tuesday in the form of a dynamic clipper system. Confidence in precipitation has increased significantly, with rain chances now exceeding 80 percent. Mid-level lapse rates of 6.5 to 7 C/km will support modest instability, making isolated thunderstorms a possibility over central and northeast Wisconsin. Showers may linger into Tuesday night, particularly across the far north, before the system exits to the east.

A shift in the large-scale pattern is expected late next week as the persistent eastern trough flattens and a warming ridge over the western United States shifts eastward. This will result in a pronounced warming trend starting Thursday, with high temperatures likely reaching the 70s to near 80 degrees by next Saturday. This warmer airmass will lead to increasing instability by the end of next weekend, though uncertainty remains regarding the timing of the next round of organized precipitation.

AVIATION
for 18Z TAF Issuance Issued at 1208 PM CDT Sat May 9 2026

A deep upper trough will be present across the region over the next 24 hours. High-based fair weather clouds with bases ranging from 4.5 to 6 kft AGL early this afternoon will increase to 8-9 kft by 21-22Z. Deep mixing will result in gusty northwest winds between 22-27 kts at all terminals through 23z.

Clearing skies are expected this evening as nocturnal cooling sets in and winds diminish. Winds will remain light from the west to northwest overnight. While VFR conditions will prevail at most sites, some scattered MVFR lake effect clouds may drift into far northern Wisconsin near the U.P. border late tonight.

On Sunday, VFR clouds will redevelop by mid-morning. Widely scattered light showers or sprinkles are possible after 15z, primarily north of a KRHI to KGRB line. Winds will become gusty again from the northwest by late morning, reaching 15-20 kts.

Confidence is high in VFR flight categories through the period.

FIRE WEATHER
Issued at 116 PM CDT Sat May 9 2026

Elevated fire weather conditions are the primary concern through the remainder of the afternoon. A dry airmass is in place behind the departing cold front. Deep mixing will allow dewpoints to drop, resulting in minimum relative humidities in the 25 to 35 percent range away from the immediate Lake Michigan shoreline.
Combined with northwest wind gusts of 25 to 30 mph, conditions will be favorable for fire development. Winds will diminish this evening with the onset of nocturnal cooling, providing some reprieve. Low afternoon humidities are also expected on Sunday and Monday though winds will be less than today.

GRB WATCHES/WARNINGS/ADVISORIES
Frost Advisory from 3 AM to 8 AM CDT Sunday for WIZ030-031- 035>037-045.