textproduct: Twin Cities

KEY MESSAGES

- Dense fog/freezing fog will be the primary concern through at least midday. Mild December weather continues today.

- A winter storm will bring several inches of accumulating snow, gusty northwest winds, and hazardous travel conditions Sunday into Monday. A Winter Storm Watch has been issued.

- Colder air returns midweek, with morning lows forecast to fall below zero to open the New Year.

DISCUSSION

Issued at 334 AM CST Sat Dec 27 2025

Gloomy, but Mild Today & Tonight...The primary near-term concern to open the weekend is the presence of widespread dense fog across central, western, and southern MN. A Dense Fog Advisory was issued and expanded by the evening shift and runs through noon. The combination of dense fog and sub-freezing air temperatures has resulted in a freezing fog scenario that is creating isolated slick spots on roads. Temperatures will gradually warm through the morning and should help limit the slick travel scenario across southern MN. On the flip side, sub-freezing temperatures are forecast to linger a tad longer along and north of I-94, so would not be surprised if reports of slick spots continue across this portion of the forecast area until mid-morning. The remainder of the day will be quite gloomy, as low clouds remain locked in place. Mild late-December temperatures will climb into the upper 30s/lower 40s across central MN/western WI and the mid to upper 40s across southwestern MN. An area of low pressure is progged to slide across northern MN later today and will support the development of drizzle across eastern MN and western WI.

Winter Storm Sunday into Monday...Attention turns to the headline making winter storm system that aims to impact holiday travel plans to end the weekend. The forecast has evolved rapidly over the past few model cycles and the general consensus is that the potential for several inches of accumulating snow across eastern MN/western WI is trending up. In addition to accumulating snow, strong northwesterly winds are forecast to gust between 35-45 mph resulting in reduced visibility and potential white-out conditions, further complicating the travel situation. A Winter Storm Watch was issued across the entire forecast area, though the watch rationale varies based on location. For eastern MN/western WI, the watch was issued for snow accumulations of 6"+. For western and southern MN, a Winter Storm Watch designated for blizzard conditions was issued due a forecast with some accumulating snow and stronger winds. We'll dive deeper into the meteorology later in this discussion, but the bottom line is that confidence has increased in a high impact winter storm to close the holiday weekend.

Winter Storm Setup: GOES water vapor imagery captures a shortwave trough digging over the Pacific Northwest, which is located within a longwave trough that extends to the southwest of California. Broad ridging extends east of these features over the central CONUS. The other synoptic feature to note is the flow of moisture within the southern stream jet that can be seen extending from the central Plains to the southwest through the Baja California region. Guidance is in strong agreement that the shortwave over the Pacific Northwest will dig southeast and phase with the southern stream jet over the central CONUS Sunday prior to strengthening into deep closed upper low over the Great Lakes Monday. Locally, the big change in the forecast data over the past ~24-36 hours is the upper-trough taking on more of a neutral tilt, which promotes a continued strengthening of the system than was depicted in earlier forecast cycles. We can quantify the nature of the strong dynamics involved in this system by looking at the evolution of the surface low, which is forecast to to deepen by ~20mb between 12z Sunday to 12z Monday. The surface low is progged to track from western IL (initially around 1000mb) northeast into northern MI, with several guidance members suggesting that the low will deepens into the mid-970mb range. Even the more conservative solutions, such as the AIFS, capture a low near 980mb by 12z Monday. The anticipated evolution keeps our forecast area on the cold side of the storm system following the passage of a cold front Sunday morning. An expansive deformation shield of snowfall northwest of the surface low will be the primary driver of our snow forecast.

Timing & Snowfall Amounts: A strong cold front will translate from west to east across the region late tonight through early Sunday. Precipitation is forecast to develop along/behind the front, initially as freezing drizzle and then quickly transition to snow as cold advection increases. Should see some accumulating snow across western MN, though it's eastern MN and western WI where the better chance for several inches of accumulating snow exists. This is due to proximity to the deepening surface low to the east over the Great Lakes, which will lead to better snowfall rates and a longer duration snowfall. Forecast soundings capture the depth of the cold advection as the low to mid level profile continues to cool through Sunday night. As a result, the DGZ is forecast to span nearly the entire length of the lowest 12k feet of the atmosphere by Sunday evening. While the thermo scenario is of high confidence, moisture remains one of the key areas of uncertainty. Global ensembles and machine learning counterparts are a running a bit more conservative on the QPF side, with say a half inch or so of moisture to work with across the eastern half of the CWA. On the flip side, various deterministic models suggest a band of QPF upwards of 1 inch. While this isn't out of the realm of possibilities, we do give some pause to the most bullish solutions as it appears likely there will be a fairly widespread convective footprint across southern portions of the Midwest. Nonetheless, the Grand Ensemble consensus of ~0.4-0.7" of QPF supports the need for a Winter Storm Watch with an SLR of a 10:1... and we anticipate SLR's for this event will be closer to the ~15:1 given the magnitude of cold air advection. Putting all the pieces together, our snowfall forecast has increased quite a bit this morning. Amounts in excess of 6" (perhaps up to 8" or so) are most likely along and east of I-35 across east central MN and western WI. 3-6" of snow is forecast across central/south central MN, and 1-3" across far western MN.

Strong Northwest Winds: Given the nature of the strong dynamics in play, the wind fields will be quite elevated and will add to the hazardous nature of the travel conditions. Northwesterly winds are forecast to sustain between 20-30 mph and gust between 35-45 mph across southwestern portions of MN. Slightly lower speeds, sustaining 20-25 mph and gusting 30-40 mph, will be expected across eastern MN into western WI. The winds will combine with falling snow to create a significant reduction in visibility during the period of falling snow. Additionally, blowing snow will be a concern as the system departs, since northwesterly winds look to remain breezy Monday. Should forecast trends continue, we anticipate brief periods of white-out conditions for all locations. However, the greatest potential for blizzard conditions will be across western and southern MN, where the winds will be the strongest.

Cold Heading into the New Year...Accumulating snow ends early Monday, though breezy northwest winds will continue. Air temperatures are forecast to fall below zero across northwest portions of the forecast area by Monday morning. Elsewhere, morning lows in the single digits are expected. Winds chills will be as cold as -15 to -25 below. Air temperatures recover and warm into the upper 20s on Tuesday, however a blast of colder air returns to close December and open the New Year. High temperatures in the teens and sub-zero lows are forecast for the second half of the week.

AVIATION /18Z TAFS THROUGH 18Z SUNDAY/

Issued at 1140 AM CST Sat Dec 27 2025

IFR conditions are likely to stick around for all but KRWF today with fog and low stratus persisting. Those who do manage to get out of IFR will come back down quickly overnight with widespread IFR/LIFR conditions ahead of our rapidly evolving winter storm for Sunday. Snow may briefly mix with rain at precip onset (10-14z) before changing over to all snow. Snowfall rates could approach 1/2" per hour for KMSP as well as our Wisconsin sites, but this is more likely just beyond the end of this forecast period. Winds will become quite strong out of the northwest by mid morning with gusts of 30-35kts through Sunday evening.

KMSP...IFR cigs continue with fog returning this evening. Precip will start sometime around 12z with a RASN mix expected at onset before becoming all snow. The window for heaviest snowfall will be between 17z-21z. Light to moderate snow is expected to continue through Sunday evening along with the gusty winds mentioned above.

/OUTLOOK FOR KMSP/ MON...IFR/-SN early, bcmg MVFR. Wind NW 15-20G35kts. TUE...VFR, chc MVFR/-SN. Wind SW to NW 5-10kts. WED...MVFR, chc IFR/-SN. Wind NW 10-15kts.

MPX WATCHES/WARNINGS/ADVISORIES

MN...Dense Fog Advisory until noon CST today for Benton-Blue Earth- Brown-Carver-Chippewa-Douglas-Faribault-Freeborn-Kanabec- Kandiyohi-Le Sueur-Martin-McLeod-Meeker-Mille Lacs- Morrison-Nicollet-Pope-Renville-Rice-Scott-Sherburne- Sibley-Stearns-Steele-Stevens-Swift-Todd-Waseca-Watonwan- Wright. Winter Storm Watch from Sunday morning through Monday morning for Anoka-Benton-Blue Earth-Brown-Carver-Chippewa-Chisago- Dakota-Douglas-Faribault-Freeborn-Goodhue-Hennepin-Isanti- Kanabec-Kandiyohi-Lac Qui Parle-Le Sueur-Martin-McLeod- Meeker-Mille Lacs-Morrison-Nicollet-Pope-Ramsey-Redwood- Renville-Rice-Scott-Sherburne-Sibley-Stearns-Steele- Stevens-Swift-Todd-Waseca-Washington-Watonwan-Wright- Yellow Medicine. WI...Winter Storm Watch from Sunday morning through Monday morning for Barron-Chippewa-Dunn-Eau Claire-Pepin-Pierce-Polk- Rusk-St. Croix.