Marine Weather and Tide Forecast for Duluth, MN

UPDATE
Issued at 819 AM CDT Fri May 23 2025

Increased cloud cover across the Arrowhead of Minnesota, western Lake Superior, the Apostle Islands, and into Iron county with a fairly expansive area of low level cloud cover propagating to the southwest around the surface high pressure system. The main impact are cooler high temperatures in the 50s for the aforementioned areas and a bit higher relative humidity values as well.

DISCUSSION
Issued at 359 AM CDT Fri May 23 2025

Not much change since yesterday morning. High pressure at the surface and a cutoff low aloft anchoring a high-latitude Omega Block persists today and Saturday. Very dry conditions will continue as air from the Canadian Shield advects into the Northland. Afternoon minimum RH values will be between 20 and 35 percent where skies stay clear to partly cloudy. In the eastern Arrowhead and eastern portions of northwest Wisconsin clouds will restrict temperatures and see min RH values between 30 and 45 percent. A few sprinkles or light rain showers are possible this afternoon due to weak cold air advection aloft and cyclonic flow. Highs today will be in the low to upper 60s, except for portions of the eastern Arrowhead and northwest Wisconsin where a lake breeze will limit temps to the middle 50s to around 60 degrees. Areas of frost are possible once again tonight and another Frost Advisory will likely be needed. Similar conditions are expected for Saturday. There will be a little more afternoon instability to support isolated to scattered rain showers. Greatest chance for precipitation will be in the Arrowhead. Several models hint at a few storms being possible along the lake breeze in the afternoon. Storms are not anticipated to be severe, though cloud to ground lightning will be a concern. Afternoon RH values will be dry once again. Highs will trend a few degrees warmer than today.

The blocking pattern aloft is forecast to break down on Sunday.
That will not break us out of the doldrums. The main branch of the subtropical jet will remain well to our south. By early next week a split flow pattern will emerge pushing the southern branch of the subtropical jet even farther south and taking a northern branch into northern Canada. Temperatures will continue to trend a few degrees warmer each day through the holiday weekend. Low RH values and small chances of sprinkles will persist.

The split flow pattern will remain in place through the remainder of the forecast. As a result, no noteworthy changes in the forecast are anticipated. Longer term models suggest a more active pattern will develop during the first week of June. As of this morning, that appears to be the next best chance for widespread appreciable rainfall.

AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
Issued at 624 AM CDT Fri May 23 2025

VFR conditions are expected through early Saturday morning.
There is a 10% chance of VFR rain showers at INL, HIB, and DLH this afternoon. Winds will be gusty from late morning through the afternoon. Fog may develop at DLH and HYR early Saturday morning. Fog is more likely at BRD and HIB where wind should be calm during the early morning hours.

MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/
Issued at 359 AM CDT Fri May 23 2025

High pressure will continue to be the main feature of the forecast over the next several days. Winds will generally be 10 knots or less with gusts of 17 knots or less. No hazardous conditions are expected over the next 7 days.

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

DLH WATCHES/WARNINGS/ADVISORIES
MN...Frost Advisory until 9 AM CDT this morning for MNZ010>012-018- 019-025-026-033>038.
WI...Frost Advisory until 9 AM CDT this morning for WIZ001>004- 006>009.
MARINE...None.