textproduct: Duluth

KEY MESSAGES

- Isolated showers and a couple embedded storms ending early this morning in Northwest Wisconsin.

- Patchy dense fog expected to develop early this morning and linger through shortly after sunrise today.

- Isolated showers/embedded storm or two could graze inland northwest Wisconsin this afternoon. Otherwise, dry weather today through Wednesday.

- Additional chances for scattered showers and storms possible Thursday into Friday. Can't rule out a few diurnal showers in the Arrowhead Saturday.

DISCUSSION

Issued at 127 AM CDT Tue Aug 18 2026

Current Overnight - Today:

Ongoing showers and the occasional embedded thunderstorm in northwest WI during the current overnight will gradually exit to the southeast early this morning prior to sunrise. These are occurring ahead of a cold front currently situated in central to northeast MN. Additional accumulations of largely 0.1-0.2" or less are expected. Behind this, some isolated showers/decaying storms currently near the southeast ND/west-central MN border track southeast during the early to late morning hours, and could graze our far southern areas from the Brainerd Lakes to inland northwest Wisconsin. Little to no accumulations expected as the majority of them are currently forecast to remain just south of the Northland. We could also get grazed by some isolated shower/weak embedded storm development in inland northwest WI this afternoon, but the potential remains around 20% or less.

Otherwise, expect some patchy fog development, some dense, through early this morning as calm winds and pockets of clearing skies combine with low-level moisture from recent rainfall. Fog dissipates shortly after sunrise today.

Today will be drier and seasonal in the wake of the cold front as high pressure begins to move in, with high temperatures in the low to upper 70s. Northwest winds gust up to 15-20 mph this afternoon then drop off quickly this evening. Cloud cover gradually diminishes from north to south this morning, though late morning-early evening diurnal cumulus then create partly cloudy skies.

Tonight - Early Thursday:

Mostly clear to clear skies set up Tuesday night along with light winds under high pressure in a cooler airmass. Due to this, we have dropped the low temperature a couple degrees into the low to upper 40s for most of the area and slightly warmer near Lake Superior. The typical cold spots could touch the upper 30s, and there is a 10% chance that those coldest spots could see some frost. Wednesday night will also be on the cooler side, but several degrees warmer (mid-40s to mid-50s) due to weak overnight southerly winds and some increasing cloud cover. Also can't completely rule out a 10-20% chance for a few showers in north-central and northeast MN Wednesday night into early Thursday as weak shortwave troughing energy moves through northwest flow aloft, but low-level dry air would likely preclude any precipitation aloft from reaching the ground.

High temperatures in the low 70s to around 80 F are forecast for Wednesday, and will be a touch higher on Thursday as low-80s are likely in the Brainerd Lakes east to northwest WI.

Thursday PM - Saturday:

Our next round of scattered shower and thunderstorms are favored to arrive in the Northland Thursday afternoon as a warm front moves through the area and cold front starts to move in late from the west. These fronts will be in association with a surface low pressure moving near or through the area. Then additional potential for showers and storms arrive on Friday as the cold front moves through the remainder of the Northland. The pattern at this time does not appear to favor strong to severe weather potential on Thursday PM or Friday, but that will depend on the timing of the warm sector of this system (late daytime Thursday or Thursday night) and how quickly the front moves through on Friday in relation to peak heating/instability. Since this system looks to be progressive without anomalous moisture (PWATs only around 1-1.25"), rainfall amounts should be on the more tame side as probabilities for >0.25" are only 30-60% and >0.5" at 20-40%. Localized areas that see thunderstorms could see amounts approach 1", but widespread soaking rainfall is not anticipated.

Showers may linger in the Arrowhead and parts of northwest WI on Saturday as some shortwave energy aloft moves through in association with an upper-low/trough in northern Ontario, with peak potential in the afternoon with peak daytime heating. However, little to no additional accumulation is expected.

Early Next Week:

Generally northwest flow aloft with ridging over the western CONUS and troughing to the east. This could bring a return of periodic rain chances through the Northland as waves of vorticity/energy aloft move through the northwest flow. However, poor agreement amongst ensemble members regarding amplitudes of these waves and their timing/locations relative to the Upper Midwest keeps forecast confidence low in this timeframe.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 630 AM CDT Tue Aug 18 2026

Patchy fog is expected to clear within the next 1-2 hours as daytime heating begins. VFR conditions are expected through the day into this evening, with northwest winds occasionally becoming gusty in the afternoon. Another round of patchy fog will be possible tonight as clear skies allows for excellent diurnal cooling to occur and winds become light.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 127 AM CDT Tue Aug 18 2026

Lighter northwest winds early this morning turn southwesterly by late morning through early evening, with gusts near Grand Marais to Grand Portage gusting to 20-25 kt along with waves of 1-3 ft this afternoon into early evening. Given this short window of stronger winds, a Small Craft Advisory has been issued. Winds shift to the northwest and become lighter again tonight into early Wednesday, then repeat the process of turning southwest Wednesday afternoon into early evening, albeit slightly weaker at 10-20 kt. Winds become light and variable Wednesday night and northeast on Thursday, but remaining fairly light at 5-15 kt. Scattered thunderstorm chances return by late Thursday/Thursday night.

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

FIRE WEATHER

Issued at 127 AM CDT Tue Aug 18 2026

Predominately rain-free weather for today and Wednesday behind a cold front as high pressure moves into the region. Can't rule out a 10-20% chance for stray showers grazing the Brainerd Lakes to northwest Wisconsin starting early this morning through late morning, with additional isolated shower chances in inland northwest Wisconsin this afternoon, but these chances could also remain south. Any accumulations would be minimal at best. Patchy fog, some dense, dissipates shortly after sunrise today. Cloud cover gradually clears from north to south through this morning, though scattered diurnal cumulus is expected to develop late this morning through early evening. Expect minimum RH this afternoon to dip to 30-45%, lowest in the northwest Wisconsin Pine Barrens and northeast Minnesota. High temperatures warm to 70-78 F today, warmest in southern areas. Northwest winds gust to 13-18 mph this afternoon into early evening then become light again tonight. Expect a cooler night tonight with lows in the 40s for most locations, with some upper-30s in the typical coolest spots. RH recovers above 90% tonight.

Deeper mixing is expected on Wednesday, though west to northwest winds will largely be under 15 mph. A couple pockets of 15-18 mph gusts can't be ruled out in the Arrowhead during the afternoon into early evening. Highs in the 70s to around 80 F are forecast. Given the deeper mixing, min RH dips to 30-40% for most locations on Wednesday. Portions of northwest Wisconsin, particularly the Pine Barrens, could dip into the upper 20s for min RH. Light winds return Wednesday night with RH recovering above 80-90%.

Another round of scattered showers and storms are likely late Thursday into Thursday night, and possible on Friday with a cold front. Amounts will largely be around 0.25-0.5" or less for most locations, though anywhere that gets thunderstorms could see very localized amounts up to around 1".

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 3 PM this afternoon to 7 PM CDT this evening for LSZ140.