textproduct: Duluth

KEY MESSAGES

- Scattered showers and storms this morning with areas of dense fog near Lake Superior

- Increased threat for strong to severe storms across northern MN and the South Shore this afternoon and evening. A Marginal Risk (1 out of 5) is now outlined for primarily a hail threat from 3PM to 8PM. However, there is some potential for surface based convection leading to damaging winds and an isolated tornado risk

- More severe weather possible Tuesday afternoon and evening with large hail in excess of ping pong ball size. Depending on where the boundary sets up we could see heavy rainfall moving across the region leading to increased flooding concerns across the South Shore and the Arrowhead.

DISCUSSION

Issued at 302 AM CDT Sun Apr 12 2026

Current Conditions:

Broad warm air advection continues over the region this morning with isentropic forcing for ascent producing rain showers with some embedded thunderstorms. The thunderstorms are confined to the tip of a low level jet running into NW WI. Storms within this area have remained elevated in nature with bulk shear of around 40 kts. Paired with mid level lapse rate of around 7.5C/km and some updraft helicity has lead to some small hail production. The low level jet will weaken and shift off to the east in the latter morning hours with rain chances tapering off.

Today:

Warm air advection will continue to overrun the area through the day as a surface low pressure ejects out of the Red River Valley into Northern MN. This surge of warmth will lead to highs climbing into the 70s across our south with cooler temperatures into the 40s and 50s as you get closer to Lake Superior. South to southwest flow through most of the day will keep low clouds engulfing the region and may lead to dense fog through the morning, especially for areas near Lake Superior.

Rain and thunderstorm coverage remains contested among the CAMs for today. The continued isentropic lifting for ascent will be present through the day which will maintain some low to medium PoPs. The aforementioned surface low will end up in phase with an upper level trough around peak heating over northern MN. This seems to be the best chance for some strong to severe storms to develop as this corridor will have adequate instability and shear. Sounding profiles would suggest the warm nose in place would likely lead to elevated thunderstorms with hail being the main threat. But there is a small window for some of these storms to become surface based along the frontal boundary. If storms do manage to become surface based then all modes of severe will be in play. Main threat window will be between 3PM and 8PM.

Monday:

Another active day will be on tap as another low pressure infringes on the Northland out of the Central Plains. A warm front will span west to east and slowly march north into our southern counties in the afternoon with dewpoints of 60F knocking on our door step. This corridor of high instability will have bulk shear values of 50-60 kts to help sustain supercell development. Mean storm flow is expected to be out of the southwest leading to some discrete cells initially that will congeal into a linear mode later into the event. However, evolution of the storm system remains a point of debate amongst the CAMs as they continue to flip flop with boundary location. If storms do manage to develop and move off this boundary into our region then hail looks to be the primary threat with wind being the secondary threat. LHP values of 16 combined with steep mid level lapse rates of 8.5C/km will be able to generate some large hail of at least golf ball size if not higher. One of the other big questions will be the progression of the low as it will drag the frontal boundaries either into our CWA or south. If it manages to push north then we could see some hefty rain rates into NW WI which may prompt some flooding concerns depending on how much moisture and snowmelt we record for today.

Tuesday:

Not completely quiet on Tuesday but less active then Sunday and Monday. An upper level trough slides in from the Northern Plains Tuesday morning which will produce some light rain. This system does not have much instability to work with so not expecting severe weather at this time. Weak elevated instability may lead to a few rumbles of thunder though. Tuesday night is when we get a bit of divergence in model depiction with the deterministic 00Z runs largely keeping surface high pressure over the Northland and shunting activity to our south. But a look at the AIGEFS and ECAIFS show a surface low moving across the Midwest and having its northern precipitation shield crossing into the Northland Tuesday night.

Midweek into the extended forecast:

Our perpetual active pattern has no quit in sight as additional systems work their way through the Midwest Wednesday through the weekend. Details and placements of the main synoptic drivers remain in flux but the late Friday into the weekend system looks to carry some cold air on its backside. This could reintroduce some snow fall back across the Northland with light accumulations Friday night as lows drop into the 20s. Any snow that does manage to fall will not linger long as we warm back into the upper 30s and low 40s for Saturday.

AVIATION /06Z TAFS THROUGH 06Z MONDAY/

Issued at 556 AM CDT Sun Apr 12 2026

Low ceilings and fog will likely be a mainstay for the morning as warm air advection floods the region from the southwest. Radar shows a line of storms along the MN/WI border that may clip HYR this morning. Afterwards broad scale lift across the region may lead to some showers at times through the afternoon and evening hours. A low pressure moving across northern MN this afternoon could also incite some thunderstorms that would be strong to severe based on the forecasted environment. The window for this activity is very short with activity quickly dwindling in the overnight hours. At which low ceilings will return once again.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 302 AM CDT Sun Apr 12 2026

Active weather pattern continues for Lake Superior with multiple chances for showers and storms. A low pressure moving across northern MN today will see an increase in southerly winds this afternoon along the South Shore that could briefly lead to a few gusts of around 25ks from. But not a lot of confidence that this will bleed over into the nearshore waters, best timing would likely be between 3-6pm. A cold front will cross over the Lake this evening with wind directions changing to out off the west and southwest by Monday morning. Another direction shift to out of the northeast as a low pressure moves across MN in the afternoon, this may lead to some funneling of the winds at the head of the Lake and warrant some Small Craft Advisories

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

FIRE WEATHER

Issued at 302 AM CDT Sun Apr 12 2026

No fire weather concerns at this time. Active weather pattern remains in place with multiple rounds of showers and storms keeping conditions moist through midweek.

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

HYDROLOGY

Issued at 345 AM CDT Sun Apr 12 2026

No changes to the Flood Watch for Bayfield, Ashland, and Iron counties in Wisconsin for this evening through early Wednesday morning. The watch remains medium confidence as it will be less the traditional sense for flash flooding potential and more into the potential for around 1-2" of rain over several days combined with the potential for 1-5 inches of snow water to melt out of the remaining snowpack. Given the convective nature of the precipitation, some pockets of locally higher and lower rainfall totals will be possible. The precipitation from this morning will set the stage for subsequent rounds of flooding potential. However, the QPF trends continue to shift further southeast with each model subsequent model run. The main threat still looks to be Monday night as a low pressure system moves across MN. A few of the deterministic models are painting 0.50-1.00" within a 12 hr period.

We will still need to monitor for river rise/flood concerns along the North Shore as well given the deeper snowpack to 12-24"+ of snow depth and snow water equivalents of 5-7"+ there. However, the trend has been for the heaviest rain to remain south of the North Shore. Additionally, despite temperatures forecast to be above freezing for several days in a row, Lake Superior will keep the North Shore high temperatures about 10-20F colder and low temperatures 5-15F colder than areas farther inland. This should slow the snowmelt process there relative to the South Shore. Should precipitation forecasts and/or temperature forecasts increase for the North Shore for tonight through Wednesday, then flood headlines may be needed.

As for river and stream concerns, the highest potential for minor flooding remains with the Tyler Forks near Mellen, which could see minor flooding by late Monday or early Tuesday depending on how heavy the first couple rounds of rain are. The Bad River and Nemadji Rivers also have some potential to rise into action stage in the Monday to Tuesday timeframe depending on heavy rain locations and amounts.

DLH WATCHES/WARNINGS/ADVISORIES

MN...None. WI...Flood Watch through Wednesday morning for WIZ002>004. MARINE...None.