textproduct: Duluth

KEY MESSAGES

- Near-critical fire weather conditions continue today. A Fire Weather Watch is in effect for tomorrow around the Brainerd Lakes due to breezy southerly winds and critically dry relative humidity.

- Strong to severe thunderstorms may be possible on Thursday afternoon and evening as a cold front moves through the area. A Marginal Risk is in effect for much of the area.

- Cooler, yet seasonable, temperatures are expected to move in on Friday and persist into early next week with additional chances for rain.

DISCUSSION

Issued at 258 PM CDT Tue Apr 21 2026

Fire weather concerns today through Wednesday:

Near-critical fire weather conditions continue today as a very dry airmass lingers over the CWA. Latest surface analysis reveals high pressure over northern MN, which has allowed for dry air advection to occur into the CWA from Ontario. Widespread min RH values below 20% are expected this afternoon due to this dry air mass and moderately deep mixing to around 5,000 feet. Fortunately, northerly winds have been relatively light today, especially in comparison to the breezy southerly winds yesterday. Therefore, a Special Weather Statement for near-critical fire weather conditions remains in effect today in northeast MN, where dry fuels are of particular concern.

A 500mb ridge, currently centered over the High Plains, will be shifting eastward into the CWA tomorrow ahead of an approaching deep trough. With winds shifting to the south on Wednesday, this will allow for WAA to occur and increase high temps into the 70s to around 80 across much of the area. The exception to these 70+ degree temps will be along the North Shore where cool air moving inland from Lake Superior will keep highs tomorrow around 10-15 degrees cooler than locations farther inland in the Arrowhead.

In addition to warm temperatures, critically dry RH as low as 20% is forecast for tomorrow. There is some degree of uncertainty tomorrow in terms of RH, notably how far north moisture will advect with the southerly flow during peak diurnal heating. In the forecast update this afternoon, opted to err on the drier side given the trend from the past couple days. One change for Wednesday will be stronger winds compared to today in north- central MN, mainly around the Brainerd Lakes area. Wind gusts up to 25 mph will be possible, most likely starting after 18z and remaining elevated into Wednesday night.

Due to the combination of critically dry RH, breezy winds, and receptive fuels, a Fire Weather Watch was issued for Wednesday from 12 PM to 8 PM in the Brainerd Lakes area, including Itasca and Aitkin Counties. If recent model trends continue and moisture advection remains fairly marginal during the daytime hours, an upgrade to a Red Flag Warning will likely be needed. Use caution with fire and follow any burn restrictions.

Severe Weather Potential and Change in Pattern:

Wednesday night will begin a change in pattern from warm and dry conditions to wetter and cooler. A deep, vertically-stacked surface low will be arriving into the Midwest late Wednesday into Thursday as the aforementioned deep trough propagates east. The first round of convection associated with this system is forecast to arrive Wednesday evening along a lifting warm front. Since there will likely be a sizable dry layer lingering in the low-levels, precipitation amounts will be limited and much of this will likely fall as virga. Instability appears to be favorable along this warm front, with some guidance suggesting MUCAPE in excess of 500mb. However, model soundings show that any potential storms will be elevated to the point where convective initiation will be difficult. The 12z HREF composite reflectivity members reflect this well, with convection being limited across the CWA.

The time period of greater concern for any strong to severe thunderstorms will be Thursday afternoon and evening as the cold front associated with the vertically-stacked low sweeps through the CWA. Conditions in our neck of the woods continue to appear marginal at best, with the arrival of best instability occurring around/after peak diurnal heating. Convective initiation is most likely to occur along the front to our west and propagate into our CWA late on Thursday. CSU machine learning probs continue to show the greatest potential for severe weather to the west and south of the CWA. The Storm Prediction Center has much of the CWA in a Marginal Risk for Thursday, which is in line with the current assessment of marginally favorable bulk shear and instability.

Following the cold frontal passage on Thursday night, high temps are forecast to be around 10-15 degrees cooler on Friday. These cooler, yet seasonable, temps are likely to persist into the weekend and early next week with additional chances for rain on Friday and early next week.

AVIATION /00Z TAFS THROUGH 00Z THURSDAY/

Issued at 629 PM CDT Tue Apr 21 2026

VFR conditions will prevail through the period. Clouds will start to increase Wednesday afternoon, but will not lead to any restrictions. Light and variable winds tonight will give way to breezy southeasterly winds starting tomorrow morning. Gusts to 15 to 20 knots are expected, highest from the Brainerd Lakes area to the western Iron Range.

MARINE /FOR NEARSHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 258 PM CDT Tue Apr 21 2026

Surface high pressure moving across northern MN will keep winds light today. Winds will increase a bit on Wednesday out of the east around 10 to 15 knots. The next period for potential hazardous conditions for small vessels is Thursday as southerly flow will lead to building waves on the North Shore. There will also be potential for strong showers and storms on Thursday.

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

FIRE WEATHER

Issued at 258 PM CDT Tue Apr 21 2026

Near-critical fire weather conditions continue today as a very dry airmass lingers, with a Special Weather Statement still in effect for northeast MN.

A wind shift is expected to gradually occur tonight as high pressure continues to move east, with winds being southerly by Wednesday morning. Min RH tomorrow will be as low as 20% as dry air lingers ahead of an approaching warm front. Southerly winds will most likely be strongest around the Brainerd Lakes, where a Fire Weather Watch is in effect on Wednesday. An upgrade to a Red Flag Warning may be needed if forecast trends hold.

Widespread showers with thunderstorms arrive on Thursday afternoon and evening along a cold front, which will likely bring a wetting rain across the region. A few storms may become strong to severe, with gusty and erratic winds and the potential for large hail. Expect cooler conditions on Friday into the weekend with additional chances for rain.

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

DLH WATCHES/WARNINGS/ADVISORIES

MN...Fire Weather Watch from Wednesday afternoon through Wednesday evening for MNZ018-025-026-033>036. WI...None. MARINE...None.