textproduct: Duluth

KEY MESSAGES

- Patchy fog this morning

- Conditional severe threat for late afternoon and evening. The greatest threat potential has shifted further south but our southern half of the CWA could still see some large hail develop between 4PM - 1 AM.

- Active pattern continues with rain showers across northern MN for Tuesday and more storms possible in NW WI Wednesday.

- A bigger system may be on the horizon for Friday which will advect warm and moist air back into the region setting the stage for some severe storms once again.

DISCUSSION

Issued at 235 AM CDT Mon Apr 13 2026

Current Conditions:

Widespread stratus is sinking in from the north blanketing the region this morning with some areas of patchy fog. Notably is the warm temperatures we still have in place with our current lows at 2 AM sitting in the 40s and 50s. Cloud cover is largely expected to endure through the morning with some scattering possible in the afternoon.

Today:

Another potentially 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. High res guidance still shows a lot of variation when it comes to the overall coverage with little run to run consistency. The latest trend has largely shifted the brunt of the impacts further south with SPC pulling the enhanced risk out of our CWA leaving us with a slight risk across our southern counties. This will all be predicated on how the warm front moves. The majority of the guidance keeps the boundary anchored to our south where the better chances for severe weather will be seen. However, even if the boundary stays to our south we could still see some development on its northern periphery with storms forming on the cool side and clustering through the evening hours. The convective parameter space does not look to have changed to much, with LHP values of 16 combined with steep mid level lapse rates of 8.5C/km will be able to generate some large hail around golf ball size. Timing has slightly shifted to later in the afternoon and early evening hours as both ridging aloft and capping will work against convective initiation. While there remains a large spread in solutions the best timing looks to be 4 PM along the boundary (which may be to our south). The end of the threat period is expected to be around 1 AM. The key to this whole forecast will be monitoring the warm front, there is even potential for storms to become surface based along the boundary which could result in a few tornado spin ups and damaging winds. But as of right now most guidance keeps this boundary to our south.

Tuesday:

Monday's low pressure system broadens and moves into central WI. A trailing inverted surface trough will end up in phase with an upper level trough moving out of the Red River Valley Tuesday morning. This combination with some added divergence aloft from an upper level jet will lead to some rain showers cruising across northern MN. There is some weak instability in the morning so a few rumbles of thunder can't fully be ruled out, but this instability does not linger long as these showers travel east through the afternoon. Overall, not expecting much in the way of impacts from these additional showers.

Midweek into the extended forecast:

The active pattern doesn't stop on Wednesday with another system working its way across the Midwest. A deeper trough will dig down into the Central Plains as a surface low slides across southern MN. This low will have a warm front branch into our region once again that will help to incite some showers and storms in the afternoon. Early look at the parameter space shows some weak MUCAPE to support some elevated storm development. Bulk shear will be around 45 kts to help sustain some storm development with mid level lapse rates increasing in the late afternoon and evening as the upper level trough pivots. Some hail productions can't be ruled out at this time.

By Friday we are looking at a very elongated system moving across the Plains that will likely draw in some gulf moisture. The surge of southerly winds will push our high temps into the 60s and 70s. Early AI NWP outlooks are painting NW WI for potential severe thunderstorms, which seems reasonable given the timing of the frontal passage among the deterministic guidance. On the backside of this system we will see a reintroduction of cold air from the NW with overnight lows dropping below freezing. Lingering moisture could wrap around into some snow showers. Given our warm temperatures through the forecast it is very questionable whether any of this would be able to stick. And even if it does we quickly warm back up into the 40s for Saturday and some 50s for Sunday.

AVIATION /06Z TAFS THROUGH 06Z TUESDAY/

Issued at 554 AM CDT Mon Apr 13 2026

Satellite shows a LIFR/VLIFR stratus deck engulfing the Northland this morning with some pockets of fog. The latest guidance holds onto this stratus deck through most of the forecast period with some potential for some MVFR conditions in the afternoon. There are some chances for showers and storms this afternoon again, but confidence is not very high in the overall coverage that we will see for this activity. High res models show very little consistency with placement of features. What we do know is that a warm front will be draped through MN, if that boundary manages to push far enough north we could see some strong to severe storms develop. For now, trends would suggest that HYR could see this action but the other terminals may be too far from the boundary and could just end up with some showers and a few embedded thunderstorms.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 235 AM CDT Mon Apr 13 2026

Areas of dense fog across the Lake this morning. This is expected to persist until late morning when it starts to erode. A low pressure moving across southern MN into central WI today will lead to an increase in northwesterly winds. Small Craft Advisories have been issued for this evening and go into Tuesday. Primary concerns are northeast winds gusting to 25 kts and building waves to 4 ft.

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

FIRE WEATHER

Issued at 235 AM CDT Mon Apr 13 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 342 AM CDT Mon Apr 13 2026

Over the past 72 hrs we have had a few swaths of 0.25-0.50" over our existing snowpack into the Arrowhead and the South Shore. The highest swatch of over 1" ran through Sawyer into southern Ashland and Iron Counties. There is still some potential for storms to develop late this afternoon and evening and move across our Flood Watch counties, but chances have decreased as the warm front that will be the focal point for storm initiation is projected to be farther south. Additional rainfall of around 0.50" will be possible with locally higher amounts should any storms develop. Tuesday's activity also looks to be more light rain focused on northern MN. With this in mind we have opted to shorten the duration of the Flood Watch to Tuesday morning.

An impressively warm day for Sunday has help to melt more of the snow pack. The South Shore saw temperatures climb into the 60s and 70s. And even the North Shore got in on some of the warmth action with highs capping out in the 50s. Modeled snow depth across the South Shore saw a significant decrease losing as much as 8" in just 24 hrs. The North Shore's >24" foot print has also been reduced from the Arrowhead to mainly the high terrain of the North Shore. It's hard to know the extent of how much water this has returned to the soil but across the South Shore it is likely in excess of 2".

Taking a trip through some of river gauges does show some response to this added liquid from snow melt. Across the MN sites the river heights have increase 0.5-1.0' NW WI where we saw the more impressive melting has seen rises of 2-3' across several rivers. The Tyler Forks River near Mellen WI is still the primary concern with a Flood Warning already in effect. This river is expected to crest on Tuesday morning just below moderate flood stage and move out of minor flooding Thursday.

DLH WATCHES/WARNINGS/ADVISORIES

MN...None. WI...Flood Watch through Tuesday morning for WIZ002>004. MARINE...Dense Fog Advisory until 10 AM CDT this morning for LSZ140>148- 150. Small Craft Advisory from 9 PM this evening to 8 AM CDT Tuesday for LSZ140-141. Small Craft Advisory from 9 PM this evening to 1 PM CDT Tuesday for LSZ142>147-150.