textproduct: Duluth

KEY MESSAGES

- Multiple rounds of strong winds are expected through this week: this afternoon and evening (west to northwest direction, Wind Advisory in effect), Wednesday afternoon and evening (southerly, not quite as strong), and through the day Thursday (northwesterly, likely strongest of the week).

- A messy clipper system will bring rain, freezing drizzle, and heavy wet snow to the Northland Wednesday afternoon through Thursday. Uncertainty is still high on exact precip types and locations.

- Temperatures warm above freezing Tuesday and again Wednesday evening/early Thursday morning before crashing back down below zero by Friday morning.

- Yet another clipper will bring a chance of accumulating snow to the Northland Friday night and Saturday.

DISCUSSION

Issued at 421 AM CST Tue Dec 16 2025

Freezing drizzle has yet to develop early this morning and at this point it appears unlikely. Cloud bases are simply too high. Radar echoes over northern Minnesota are likely above 700 mb or around 8-10kft AGL. Strong isentropic ascent was focused in that layer. However, moisture has been far harder to come by. With this forecast update we removed any remaining mentions of precipitation for this morning.

Fast-moving clippers will be the norm for the next week. We remain in fast northwest to meridional flow aloft. A large area of high pressure centered between California and Hawaii and an upstream Rex Block over the Northern Pacific will continue to compress the sub-tropical jet and keep it aimed at the Northern Plains and Canadian Prairies. A broad baroclinic zone stretching from the northern Canadian Prairies to the central Plains will provide ample potential energy for several strong clippers over the next week.

The first system on deck will feature surface low pressure currently centered over southern Manitoba propagating eastward into far northern Ontario by noon today. That system will be preceded and followed by strong low-level jets. The southwesterly first jet is located north of the warm front over northwest Minnesota and western Ontario as of 09Z and will traverse the area from west to east this morning. Winds aloft will weaken a bit once the warm front passes by. Temperatures today will soar well above normal and may make a run at record values for Hibbing and International Falls (records - HIB: 44, INL: 47). With the sun near it's seasonal minimum angle and a steep low-level thermal inversion, warm air advection will play the biggest role in max temps today. Forecast high temps range from the middle 30s in northwest Wisconsin to the middle 40s in north-central Minnesota. The warm temperatures will create a situation where ice and snow on roads melts during the day and then refreezes tonight, which may create slippery stretches on area roads.

A cold front will dive southeastward across the Northland this afternoon and overnight. Look for winds to veer northwesterly behind the front and strong cold air advection to take over. Lapse rates will steepen behind the strong cold front and will allow higher momentum air from aloft to mix to the surface. Expect wind gusts to increase behind the boundary and remain strong overnight. The northwesterly second LLJ will arrive along and behind the front and will bring 850 mb wind speeds of 50 to 60 knots. The strongest winds will be found above the thermal inversion around 825 mb or around 5kft AGL. Wind Advisories issued by yesterday's forecasters looks on track and should work out well. The steep lapse rates and additional moisture arriving behind the front should be sufficient for widespread light snow showers and flurries for tonight. There is a small chance of freezing drizzle before the column cools enough to activate ice crystal nuclei.

Attention then shifts to the next in the parade of clippers forecast to arrive Wednesday night and depart on Thursday. The cold front will stall over the Dakotas Wednesday and lift northeastward again as a warm front during the day Wednesday. Afternoon highs will be above normal once again with readings around 30 degrees near International Falls and Phillips, WI to the middle or upper 30s in central Minnesota.

A surge of moisture in the atmospheric river nosing into the Pacific Northwest will accompany that clipper as it propagates eastward. The majority of the moisture available Wednesday night and Thursday will be of Pacific origin. Strong poleward low- level flow will bring a slug of Gulf moisture northward into the Mississippi River Valley. However, the remnant cold front from today's system will likely set the stage for thunderstorms over the Mid-South tonight potentially extending northward into Illinois and Iowa for Thursday. Should storms develop, they will intercept and displace the northward moisture feed from the Gulf before it can reach areas where it would influence precipitation over the Northland. Storms would likely shunt the low pressure system track a bit farther south in response to the robust heat release from the storms.

At this point we are fairly comfortable with the idea of a swath of 2 to 5 inches of snow Wednesday night and Thursday as that system traverses the region. Warm air ahead of the system and potential loss of cloud ice behind the system's cold front may result in two periods of freezing drizzle Wednesday night through Thursday evening. The odds of freezing drizzle are generally around 20 percent as of this morning.

The other big story with the second clipper will be the strong winds. As alluded to in earlier discussions the low-level jet associated with the clipper will unusually strong with 60-70 knot winds. That's around a 3% occurrence probability this time of year (based on NAEFS climatology). Expect gusty winds ahead of the system on Wednesday and behind the cold front Wednesday night and Thursday. The strong and gusty winds will be able to blow the freshly fallen snow around and may result in reduced visibility.

Temperatures trend colder for Friday as high pressure very briefly returns. The next clipper is forecast to move over the region Friday night and Saturday. Accumulating snow and gusty winds will be a concern once again. The Pacific NW atmospheric river will drift southward and weaken slightly over the weekend before surging north early next week. Another bolus of moisture is forecast to eject over the Rockies and into the Northern Plains and southern Canadian Prairies early next week, which may set the stage for another clipper snow event Monday night and Tuesday.

AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/

Issued at 603 AM CST Tue Dec 16 2025

Two very strong low-level jets will affect the terminals today through early evening. The first jet is a southwesterly LLJ with a core wind speed around 60 kts. The winds aloft will weaken slightly after that jet axis passes east of the terminals and then strengthen again as northwesterly second jet arrives later today. A cold front will move southeastward across the region this afternoon and tonight which will steepen lapse rates and allow strong winds aloft to mix down to the surface. The resultant increase in sustained winds will reduce the LLWS risk. The cold air advection will also be accompanied by light snow showers and flurries. Will handle this potential with a VCSH mention for now. MVFR or IFR visibility is possible with those snow showers, although as of this forecast, the potential for those conditions is less than 30%.

MARINE /FOR NEAR SHORE WATERS OF WESTERN LAKE SUPERIOR/

Issued at 439 AM CST Tue Dec 16 2025

Numerous rounds of gales and possibly storm force winds are expected through the remainder of the week. Hazardous conditions for smaller vessels will precede and follow the gales. The first round of gales arrives this morning near Grand Portage and will expand southwestward along the North Shore and into portions of the South Shore waters by late morning. The strongest winds should be along the North Shore but all of Western Lake Superior will likely see gusts in excess of 35 knots. Gusts in excess of 45 knots are possible for the North Shore. A Gale Warning is in effect.

Wind should weaken fairly quickly going into Wednesday morning but the lull wont last long. Southerly winds pick up through Wednesday afternoon. Another period of gale force gusts is possible here too. Into Thursday morning those winds remain strong and veer northwesterly then strengthen even further. By Thursday afternoon and evening gale force winds are likely over the waters. Storm force gusts to 50 knots are possible, especially for the North Shore Thursday afternoon and evening. There is a 20 to 60 percent chance of storm-force winds along the North Shore during that time. Winds should calm going into Friday morning. Additional Gale Warnings and Heavy Freezing Spray Warnings will likely be needed, especially for Thursday.

Yet another fast-moving low pressure system will bring hazardous conditions to the waters Friday night and Saturday.

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

DLH WATCHES/WARNINGS/ADVISORIES

MN...Wind Advisory from noon today to 9 PM CST this evening for MNZ010-011-018-019-025-026. Wind Advisory from 5 PM this afternoon to 3 AM CST Wednesday for MNZ012-020-021. WI...None. MARINE...Small Craft Advisory until 6 AM CST Wednesday for LSZ121-148. Gale Warning until 6 AM CST Wednesday for LSZ140-141. Small Craft Advisory until 6 PM CST this evening for LSZ142>145. Gale Warning from 6 PM this evening to midnight CST tonight for LSZ142>145. Small Craft Advisory until 10 AM CST this morning for LSZ146- 147-150. Gale Warning from 10 AM this morning to midnight CST tonight for LSZ146-147-150.