Marine Weather and Tide Forecast for Superior, WI

UPDATE
Issued at 705 PM CDT Tue May 20 2025

Winds have trended down slightly near the head of Lake Superior, with gusts at KDYT currently at 45 to 50 mph and a MnDOT sensor on the Blatnik bridge still gusting to around 50 mph. With these winds slowly easing relative to the stronger gusts earlier today, the High Wind Warning on the land side at the head of Lake Superior has been replaced with a Wind Advisory and the Storm Warning at the head of Lake Superior in the nearshore waters has been replaced with a Gale Warning.

DISCUSSION
Issued at 238 PM CDT Tue May 20 2025

This afternoon, a low-pressure system will track towards the Ohio River Valley is bringing moisture and a band of light rain to southwestern parts of the Northland. Meanwhile, high pressure over Hudson Bay is pushing drier air into the northern Great Lakes. This dry air is causing relative humidity to plummet to values of 12% in Ely and similarly across the Arrowhead region north of US 2, and to 20-25% in northwestern Wisconsin east of a line from Ashland to Hayward. PWATs are hovering around 0.10" across the International Border. Luckily instability is minimal with a very warm and stable layer aloft.

The interplay between these systems has tightened the pressure gradient, resulting in strong east to northeast winds of 15-25 mph, with gusts reaching 40-45 mph across most of the Northland.
Higher gusts are possible near the shores of western Lake Superior where gusts have been near 65 mph. These windy and dry conditions are creating critical fire weather concerns in portions of northeast Minnesota and near-critical conditions in parts of northwest Wisconsin this afternoon.

As the low-pressure system continues its eastward trek this evening, an intensifying low-level jet will help expand the band of light rainfall northward and eastward across more of the Northland and northwestern Wisconsin. This moisture is expected to bring light rain as far north as the Twin Ports, with lower chances extending from Grand Rapids to Hibbing. However, due to the drier air in the north, significant rainfall accumulation is unlikely on the northern edge of this system. Through tonight, rainfall amounts will vary, with an inch or more possible from the Brainerd Lakes to Pine City and Siren, tapering to less than a tenth of an inch from Spring Lake to Hibbing and Bayfield.

Looking ahead, this low will move eastward, while another low retrogrades across southeast Canada, reinforcing drier and slightly cooler air, particularly in the Arrowhead. Expect sunny skies and warming afternoon temperatures through the week, though mornings will be chilly, with patchy frost possible on Thursday and Friday. Fire weather may remain a concern - mainly due to low RHs as wind speeds will be much lower.

Temperatures rise through the week becoming fairly close to normal by Sunday.

AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
Issued at 1258 AM CDT Wed May 21 2025

Although easterly winds have weakened tonight, gusts of 20-30kts remain possible overnight, mainly at DLH, where strong winds near the head of Lake Superior continue. Weaker gusts are possible at other terminals. East to northeast winds increase Wednesday morning, with gusts of 25-30kts near Lake Superior, including DLH, and gusts of 17-25 kts further inland.

A northwest to southeast oriented rain band continues to slowly push westward tonight as drier air arrives from the northeast.
Light rain within the band will be accompanied by MVFR cigs and/or vis. This rain band, currently over HIB to DLH to HYR will become more oriented from BRD to HYR through the day Wednesday, with rain ending through the afternoon. Current IFR conditions at BRD will likely improve to MVFR as showers become more prominent.

Low level wind shear is possible overnight across portions of the area with strong winds off of the surface.

MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/
Issued at 705 PM CDT Tue May 20 2025

The Storm Warning at the head of Lake Superior was replaced with a Gale Warning as winds have decreased, with KDYT latest gusts to 43 knots. Expect gale-force winds to persist through the evening across western Lake Superior, and linger through Wednesday morning for the North Shore and at the head of the Lake.

Previous Discussion: Strong northeast winds continue through early Wednesday morning. Storm force winds and gales are expected across all of Western Lake Superior. Winds decrease slowly Wednesday, turning northerly and calming down into Thursday.

For the open water discussion, refer to the NWS Marquette Area Forecast Discussion at weather.gov/mqt.

DLH WATCHES/WARNINGS/ADVISORIES
MN...Wind Advisory until 1 AM CDT early this morning for MNZ012- 019>021-037.
WI...Wind Advisory until 1 AM CDT early this morning for WIZ001-002.
MARINE...Gale Warning until 1 AM CDT early this morning for LSZ121- 146>148-150.
Gale Warning until 10 AM CDT this morning for LSZ140>142.
Gale Warning until 1 PM CDT this afternoon for LSZ143>145.