textproduct: Duluth

KEY MESSAGES

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

UPDATE

Issued at 232 AM CDT Fri Sep 11 2026

Overnight and this Morning:

Quiet weather for the rest of tonight and through much of the day today, as southwesterly winds increase ahead of an approaching storm system. Winds will be breezy with gusts of 25-30 mph by this afternoon. Although clouds will be increasing, highs will still reach the upper 70s to lower 80s, with mid 70s along portions of the North Shore, under strong warm advection.

Severe storm potential for this Afternoon-Evening:

The airmass will become increasingly unstable through the afternoon, as moisture and warm air advects northward ahead of the approaching surface low and cold front. The parameter space remains unchanged from what was highlighted in the previous discussion below. What we will need to continue to watch is the strength of the cap around 750mb, as that will prevent development through much of the afternoon. As surface temps hit the low 80s, at the time where shear values are increasing, isolated cells could develop. These storms would pose the largest tornado threat, along with large hail. Storm mode will transition to more linear into the early evening, with the primary threat becoming damaging winds. This line will push eastward through the evening hours, with scattered showers hanging around portions of the Arrowhead and northwest WI for a few hours past midnight.

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 /12Z TAFS THROUGH 12Z SATURDAY/

Issued at 641 AM CDT Fri Sep 11 2026

Very widely scattered showers out there this morning, and have added some isolated pops, to reflect the isolated nature of any activity this morning. Do not expect impacts at any forecast terminal.

Skies are VFR this morning, and expect VFR conditions through much of the day, before impacts arrive from an approaching cold front. Winds will continue to increase from the southwest this morning, with gusts to 25kts by this afternoon. A period of LLWS is also possible this morning, as low level winds are elevated.

Strong to severe storms are expected to develop across the region this afternoon into the evening. Expect a period of convection at each terminal, most likely after 12/00Z. Will likely need refinements to timing this afternoon. With the rain and storms, vis and cig reductions can be expected, most like to MVFR or high end IFR cigs. A wind shift to the northwest is also expected late in the forecast period, behind the cold front.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 232 AM CDT Fri Sep 11 2026

Winds are increasing this morning, from the south to southwest, as a weather system approaches from the west. Expect gusts of 20-30 kts this morning and persisting through tonight with occasional areas where gusts may drop a little below that. Small Craft Advisories have been issued through late Friday night. There is a low chance for some gales (winds around 30kts) for a couple hours near Grand Portage this afternoon, but confidence in meeting those winds is low. Showers and storms are expected late this afternoon into tonight. 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 232 AM CDT Fri Sep 11 2026

Increasing moisture, clouds, and southwest winds expected today, as a strong weather system brings rain and storms to the region this 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 northwest winds 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 around 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 until 4 AM CDT Saturday for LSZ121- 140>148-150.