textproduct: Duluth

KEY MESSAGES

- Dangerous swimming conditions expected for the beaches of the Twin Ports today and Monday. - Frost is forecast beginning tonight and continuing through Wednesday night. The coldest night will be Monday night into Tuesday morning, when sub-freezing temperatures are forecast.

DISCUSSION

Issued at 305 AM CDT Sun Sep 20 2026

Early this morning, a weak cold front continues to push south across the Northland, We will see lingering low clouds and fog which dissipate after sunrise. Today, gusty northeast winds are expected to develop, as the cold front sags to our south and high pressure moving in from the north tightens the pressure gradient. Wind gusts of up to 35 mph are possible for the Twin Ports and South Shore areas during the daytime, with wind gusts of 20 to 25 mph farther inland. These winds will lead to another day of High Risk for rip currents for the Twin Ports beaches. A Beach Hazards Statement will again be needed for Sunday and also likely again Monday. This surge will also bring cooler and drier air into the region, with high temperatures near Lake Superior only in the upper 50s, with 60s elsewhere.

We have been seeing signals for isolated lake effect showers in the CAMs for today, but I suspect we do not yet have enough temperature difference between the surface and 850mb for true lake effects. Later today, the drier air moving in from the northeast will shut off this potential completely.

Clouds will clear from northwest to southeast tonight into Monday. Together with the high pressure building in with lighter winds and the cooler airmass, means a small area of frost is possible for the Minnesota Borderlands and interior Arrowhead by early Monday morning. Frost headlines may be needed for these limited areas pending the exact sky cover trends today and this evening. Monday will feature mostly sunny skies but cool conditions with a repeat of 50s near Lake Superior and low-mid 60s elsewhere. The northeast winds will likely give us another day with elevated rip current risk along the beaches of the Twin Ports.

The coldest night this week will be Monday night into Tuesday morning, with mostly clear skies, and light winds with the surface high pressure ridge overhead. This will lead to excellent radiational cooling overnight, which should produce widespread frost over much of the region, with even some sub- freezing temperatures in our local cold spots. Frost and Freeze headlines will likely be needed. Tuesday will remain sunny and cool with with high temperatures moderating slightly but still on the cool side. Another round of frost is possible Tuesday night into Wednesday morning with continued dry, calm and clear conditions.

A gradual warming trends begins on Wednesday as the surface high pressure ridge slides east of the area, allowing warmer air and more moisture to move back into the area. A shortwave may bring some precipitation chances back into the area on Thursday, but otherwise the forecast is generally dry for the rest of the work week, with high temperatures rising into the 60s and low 70s by Friday and Saturday. Next weekend there are some indications we may have some precipitation chances, but confidence remains low with an upper level ridge in place and generally weak features.

AVIATION /12Z TAFS THROUGH 12Z MONDAY/

Issued at 647 AM CDT Sun Sep 20 2026

A weak cold front has sagged south into northwest Wisconsin as of early this morning. Along the front, there is an area of MVFR to VFR ceilings which are being dragged south along with it. Away from the front where there are few to no clouds, we are getting some fog development, with visibilities ranging from LIFR to IFR. Another area of stratus with IFR to MVFR ceilings has sagged into far northern MN, affecting KINL and is approaching KHIB. The fog should gradually dissipate this morning, but the stratus may take longer and have not returned INL to VFR until 18z. Once this stratus lifts or sags south of the area, I expect the remainder of the TAF period to have VFR conditions. Winds will increase out of the northeast today, and will be strongest at DLH with gusts around 20 kts. Winds to diminish around 00z to 10kts or less.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 305 AM CDT Sun Sep 20 2026

Winds will increase significantly this morning for most of western Lake Superior. Northeast winds of 15 to 25 knots are forecast, with gusts reaching 25 to 30 knots in the southwest arm and along the South Shore. Waves will build to 4 to 7 feet. Small Craft Advisories are in effect. A short period of gales to 35 knots is possible but not likely from Silver Bay to Duluth and along the South Shore. Winds decrease Sunday evening, but expect lingering swell into Monday from 1 to 3 feet under continued northeast winds of 10 to 20 knots and gusts of 20 to 25 knots for the South Shore and southwest arm during the day on Monday. Additional Small Craft Advisories may be needed. The northeast winds continue on Tuesday, but speeds will be lighter.

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

FIRE WEATHER

Issued at 305 AM CDT Sun Sep 20 2026

Fire weather concerns remain low through the forecast period. Minimum relative humidity values today will remain above 50 percent, even as winds increase out of the northeast and become gusty. The strongest winds will be found near Lake Superior, where winds of 10 to 15 mph may gusts as high as 25 mph. Elsewhere, winds will be 5 to 15 mph with gusts up to 20 mph. The generally cooler conditions will continue into Monday with highs only in the 60s and with minimum RH values generally between 40 and 50 percent. Otherwise, we have a period of no precipitation through Wednesday, with gradually lowering minimum RH values, moderating temperatures and lighter wind speeds.

See the Fire Weather Forecast product for a more thorough breakdown of fire weather conditions.

DLH WATCHES/WARNINGS/ADVISORIES

MN...Beach Hazards Statement from 10 AM CDT this morning through this evening for MNZ037. WI...Beach Hazards Statement from 10 AM CDT this morning through this evening for WIZ001. MARINE...Small Craft Advisory until 10 PM CDT this evening for LSZ121- 143>148-150. Small Craft Advisory until 4 PM CDT this afternoon for LSZ140.