textproduct: Duluth

KEY MESSAGES

- There is a slight risk (level 2 out of 5) for scattered strong to severe thunderstorms Friday late afternoon and evening.

- Cooler fall weather moves in Saturday and into the foreseeable future.

- Widespread rain and thunderstorms are likely Monday and Monday night. Severe weather is not expected. Localized minor flooding can't be ruled out.

DISCUSSION

Issued at 137 PM CDT Thu Sep 10 2026

Quiet weather abounds this afternoon with weak ridging aloft. As a surface high departs and moves into the central Great Lakes tonight, we will remain under an upper level ridge, which will be strengthened by a developing low-level jet tonight under warm southwest flow. Wind speeds will increase overnight, and fog is not expected to be a concern tonight.

On Friday, warm air and moisture advection will continue with a trough and developing surface low moving our way from the west. A trailing cold front associated with a low up in Canada will combine with the warm air and moisture advection to trigger showers and thunderstorms. The trend for storm initiation continues to be later, favoring storm development around 6 PM or so. Plenty ingredients will be in place for some severe storms, including: a cold front, up to ~2 kJ/kg MUCAPE (initially surface-based), favorable 30-40 kt 0-6 km shear (with some low- level streamwise vorticity ingestion possible which could result in a low-end tornado threat), and overall plenty of moisture with PWATs inching up into the 1-1.75" range. The timing of storm initiation will be crucial, as a delay may result in a very narrow window for surface-based convection in the early evening. Large hail and damaging winds are still looking to be the main threats, especially if storms become largely elevated by starting later into the afternoon/evening. If they can get going early enough, a low-end tornado threat exists. The rain/storms should be progressive enough to minimize flooding risks, but with plenty of moisture available, any brief training of storms could result in some very localized and short-duration minor flooding, especially in developed areas. Storms are expected to move out with the cold front a bit after midnight.

The gates will open to more fall-like temperatures following the cold front into Saturday with cool northwest flow developing. Highs are likely only to reach the 60s in Minnesota and low 70s in northwest Wisconsin. We will remain in this cool air mass through the weekend with otherwise pretty quiet weather. Saturday and Sunday nights are looking rather chilly with high pressure slowly passing through at the surface. At this point, probabilities for temperatures cold enough for frost (~36 degrees) are about 10-15% for the usual cold spots. So, can't completely rule it out, but the chances are very low at this time. With that said, lows in the upper 30s are looking likely for the usual cold spots and low 40s for most other places.

Going into Monday, it's looking like we'll get a nice surge of moisture and warm air advection with Gulf of America origins. This should lead to more of a widespread light to moderate rain with some thunderstorms as well (though instability isn't currently looking overly impressive for anything strong or severe). There is some potential for locally heavy rainfall just north of the surface warm front, and there's some uncertainty where that might set up. Wisconsin is looking to be the main target right now, but whether means northwest Wisconsin or central Wisconsin is still up in the air. There could be some localized minor flooding issues with this, and part of that will depend on how much rain falls with Friday evening's storms (as of now, it looks like northeast Minnesota has the best chances, which is good news as that would spread the moisture somewhat evenly). Overall, this should be good news for ongoing drought with a good half inch of rain minimum for most places and >1" of rain very possible especially in northwest Wisconsin.

Another reinforcing cold front will pass through going into Tuesday. Some fall-style wraparound showers are possible Tuesday, then high pressure is likely to bring quiet but cool weather Wednesday and Thursday.

AVIATION /00Z TAFS THROUGH 00Z SATURDAY/

Issued at 624 PM CDT Thu Sep 10 2026

High pressure is departing the region this evening with VFR conditions across the Northland. Overnight, a low level jet ramps up out of the SE leading to widespread low level wind shear. The jet weakens tomorrow morning with the left over winds filtering down to the surface for a breezy day. Later in the forecast period expect showers and storms some of which may be strong to severe.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 137 PM CDT Thu Sep 10 2026

Some brief wind gusts around 20-22 kt are possible up near Grand Portage, otherwise wind gusts below 20 kt with south and slightly variable flow expected through this afternoon. Wind direction will be slightly variable into tonight as well, but trending southwesterly by morning and increasing in speed gradually overnight. Gusts are expected to increase to the 20-30 kt range early Friday morning and persisting through Friday night with occasional areas where gusts may drop a little below that. There's a ~30-40% chance for some gales near Grand Portage mainly Friday afternoon. Small Craft Advisories and a Gale Watch have been issued late tonight through late Friday night. In addition, showers and storms are expected late Friday afternoon into Friday night. A few strong to severe storms capable of wind gusts to around 40 kt and large hail to around quarter size are possible (there is a level 2 out of 5 risk for scattered severe storms from the Storm Prediction Center).

Winds will shift westerly to northwesterly going into Saturday. Small Craft Advisories are expected to be needed through around Saturday evening with gusts in the 20-30 kt range. A brief break in strong winds is expected Sunday, but then another potent weather system will bring rain, thunderstorms, and more strong winds Monday into Tuesday. Winds will be at least hazardous for small craft and gales are possible as well.

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

FIRE WEATHER

Issued at 137 PM CDT Thu Sep 10 2026

Minimal fire weather concerns anticipated in the next week. Some dry weather this afternoon with some similar conditions expected in northwest Wisconsin Friday, but overall increasing moisture, clouds, and rain chances are expected later Friday afternoon and evening. Some appreciable rainfall amounts are expected from thunderstorms especially in northeast Minnesota through Friday night with totals generally in the half inch to one inch range, but with locally higher amounts expected from thunderstorms. Lesser amounts are expected in northwest Wisconsin with around a tenth to two tenths of an inch, but some scattered wetting rains around a quarter of an inch are possible.

Dry and cooler weather is expected over the weekend with some breezy conditions Saturday. RH may dip into the 40-50% range for some, but with rain expected prior, fire weather conditions should be minimal. Another round of widespread rain is likely Monday into Monday night with a wetting rain likely for most and accumulations over an inch quite possible, especially in northwest Wisconsin.

High pressure will develop around mid-week with some dry and quiet weather. RH is not expected to fall much below 50%.

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

DLH WATCHES/WARNINGS/ADVISORIES

MN...None. WI...None. MARINE...Small Craft Advisory from 4 AM Friday to 4 AM CDT Saturday for LSZ121-141>148-150. Small Craft Advisory from 4 AM to 7 AM CDT Friday for LSZ140. Gale Watch from Friday morning through late Friday night for LSZ140.