textproduct: Duluth

KEY MESSAGES

- Two rounds of thunderstorms are possible today. The first round this morning into early afternoon (10-30% chance) may be strong to severe with 70 mph wind gusts and quarter size hail the main threats. There is a 30-60% chance of another round of storms this afternoon through the overnight period mainly over northwest Wisconsin. Those storms may produce wind gusts to 80 mph, hail to 2 inches in diameter, one or more brief tornadoes, and minor flash flooding.

- Warm and muggy conditions continue through the week, but do not anticipate needing Heat Advisories.

- Several rounds of showers and storms are forecast Thursday through early next week. Some of those storms may be strong to severe with the greatest risk after today found on Thursday.

UPDATE

Issued at 416 AM CDT Wed Jul 1 2026

Not much has changed with overall forecast overnight. There remains a conditional risk of severe thunderstorms potentially in two rounds. First round would be later this morning into early afternoon and the second round would be late this afternoon through the overnight.

Thunderstorms developed late last night and persist early this morning along and north of a quasi-stationary front draped over northern Nebraska to far northwest Iowa to near Houghton, MI. As of 0830Z (3:30 AM CDT) storms were located from SE South Dakota across SW Minnesota into NW Iowa. The strongest storms appear to be north of the surface front near FSD. CAMs (particularly the HRRR) are at least aware of the storms this morning, an improvement over the past several days. HRRR wants to dissipate the existing storms quickly while developing another area of storms farther east. WRF-ARW and NAMNest feature storms persisting and coverage increasing east along the Iowa/Minnesota line over the next few hours. With the development of strong storms in NE Iowa over the past hour, they might be onto something. The RAP features an convectively-driven enhancement in the 850 mb winds propagating into central Minnesota by 14Z. The REFS mean also includes this feature while the stronger 850 mb jet remains along/south of the front in northern Iowa.

A gradient of MUCAPE exists from SW Minnesota northeast to western Upper Michigan, roughly along the front. If a sufficient cold pool can develop, strong to potentially severe storms could ride along the gradient toward NW Wisconsin by 15Z. CAPE is forecast to build quickly south of the boundary today with ample heating and good low-level moisture. By early afternoon, pending the evolution of overnight convection, MLCAPE values of 2000-4000 J/kg are forecast along and south of the front. The front itself may wobble slightly north in response to early morning convection. If the storms persist, they may begin to strengthen again by the time they move into the WI/MI border area. Overall the potential for severe weather this morning is low, probably less than 5%. If severe storms do occur, they will be capable of damaging winds up to 70 mph and large hail to quarter size.

The second potential for storms arrives this afternoon through the overnight. Storms are expected to develop along or near the front. Initiation is most likely to occur to the south and west of our forecast area with storms eventually propagating into northwest Wisconsin. Ample instability and 30-40 knots of 0-6 km bulk shear will support supercells initially with gradual upscale growth into a forward-propagating MCS expected. There is also a chance storms may develop along or near the front in NW Wisconsin this afternoon before the upstream convection arrives. The kinematic and thermodynamic parameter space is a little more concerning than with the morning storms. While the potential for severe storms is conditional depending on the placement of the front, how morning convection resolves, and mesoscale forcing placement, the hazards are greater. The storms will be capable of wind gusts of up to 80 mph (in the case of an MCS) with 40-70 mph the more likely range. They will also be capable of hail up to 2 inches in diameter (in the case of supercells or embedded supercells) with a more likely range of penny to ping pong ball size. Brief tornadoes are not out of the question given clockwise curvature in the low-level hodograph (0-3km). The hodographs become less favorable for mesocyclone maintenance above 3 km, hence the brief nature of possible tornadoes. Heavy rain which could lead to localized flash flooding is also a concern.

Conditions today won't be quite as warm as Tuesday. Moderate HeatRisk (level 2 of 4) is forecast over a portion of northwest Wisconsin with maximum heat indices in the 80s to low 90s across the Northland. High temps will range from the low to upper 80s. With the front mainly to our east and south, lower dewpoints are forecast which is the main driver of the lower risk of heat- related illness. Thus no heat-related headlines are expected today.

Please see the discussion below from yesterday after for details beyond tonight.

DISCUSSION

Issued at 255 PM CDT Tue Jun 30 2026

A "cool" front is pushing eastward through the Northland this afternoon, currently from near Crane Lake to Brainerd. The airmass is a bit cooler and drier behind the front, with dewpoints in the 50s. The combination of gradient winds (with low pressure centered over southern Manitoba) and afternoon mixing as temps warm into the 80s is allowing for breezy southwest winds with gusts of 25-30mph. There is a slight CU field finally developing near INL and Lake of the Woods, but do not expect much up growth and showers are not expected behind the front.

Ahead of the front, we cannot rule out a shower or storm this afternoon and evening. The best chances for this will be across the eastern third of northwest Wisconsin, roughly east of a line from Ashland to Hayward. With drier mid level air spreading eastward, the chances for convection will remain low. Dewpoints are lagging behind expected trends, as some of that drier mid level air is already mixing down, keeping dewpoints in the 60s. Breezy southwest winds will continue, and while some low level moisture could advect northward, it will battle with the incoming drier mid level air. There is instability pooling ahead of the front, with shear values around 40kts. So, if a storm can develop or move into northwest Wisconsin, it could be strong to severe through early evening.

Better storm chances will exist Wednesday morning and likely again during the afternoon, as upper level wave pattern remains active and warm temperatures push instabilities upward over the Northland. Tonight, convection is expected to develop across southern MN and push northeastward, reaching northwest WI Wednesday morning, after 8AM. Convection will be in part driven by a low level jet, which should weaken after sunrise. There is some question on the trajectory of this activity, with it riding along the frontal boundary moving through the Northland now. It is possible the strongest part of what is expected to be a MCS will push more eastward, following better jet features, and remaining along and ahead of the front. This would bring showers to portions of northwest Wisconsin Wednesday morning into the early afternoon, but likely not strong to severe storms. Lingering boundaries could allow for development through the day, as daytime heating maintains shower and storm chances.

Another round of strong to severe storms is possible Wednesday night, with development to our south, pushing eastward into central Wisconsin. Will continue to carry higher POPs for Wednesday evening, as some activity could expand northward into the area overnight into early Thursday morning. For both rounds Wednesday and Wednesday night, all severe weather threats are possible.

For Thursday through the upcoming weekend, the upper level pattern becomes more zonal over the northern CONUS with strong ridging remaining centered over the Mid Atlantic. The Northland will remain warm with slightly less humidity. Waves within the zonal flow will allow for occasional rain or storm chances, enhanced by daytime heating in the afternoon and evening. High temperatures will remain somewhat steady in the upper 70s and 80s. While not every day will be a washout, anyone with outdoor holiday weekend plans should monitor the forecast closely.

AVIATION /12Z TAFS THROUGH 12Z THURSDAY/

Issued at 645 AM CDT Wed Jul 1 2026

An area of rain and thunderstorms over central MN as of 1130Z will continue to move northeastward and bring rain chances to BRD, HIB, and DLH this morning into early afternoon. The area of more intense thunderstorms farther south should move northeastward this morning and may pose a risk at HYR by 16-18Z per HRRR and RAP guidance. Opted for VCSH for the moment since forcing for the storms diminishes through the morning. Another round of storms may develop this afternoon and evening and could bring thunder chances back to HYR later tonight.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 1049 PM CDT Tue Jun 30 2026

Clear conditions over Lake Superior are expected to deteriorate over the night tonight as fog develops with the continued transport of warm, moist air from the south. A Dense Marine Fog Advisory is in effect until the mid morning. Winds out of the southwest will continue to be in the 10-15 kt range throughout the rest of the week, with gusts up to 20 kts along the far north shore Wednesday.

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

FIRE WEATHER

Issued at 1049 PM CDT Tue Jun 30 2026

Dry conditions are not a concern for the rest of this week with dewpoints expected to remain in the 60s. Temperatures will remain in the 80s as well for the remainder of the week, but conditions are not expected to feel as hot as earlier this week. This will lead to RHs mainly remaining above 40%, though a few spots in far northern Minnesota could see RH dip lower into the 30-35% range. Windy conditions continue out of the southwest with winds 10-15 mph and gusts up to 20 mph.

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

DLH WATCHES/WARNINGS/ADVISORIES

MN...None. WI...None. MARINE...Dense Fog Advisory until 10 AM CDT this morning for LSZ140>142.