Good afternoon everyone! This update discusses the remaining fog risks as well as the winter storm progressing across the Dakotas currently. You will find most of this information to be similar to this morning’s update with some nuances. Areas of dense freezing fog remain quite persistent across the southern and eastern portions of MN as of 12:45pm CST. This is shown by the numbers below which is visibility depicted in miles. Many locations have significant reductions in visibility, especially southwest of the Minneapolis area. Couple the fog with areas of freezing drizzle/mist, you will find slick spots on many roadways; Something to continue to keep in mind if traveling.
Snow coverage also continues to expand eastward with many areas in ND, especially the northern portions of the state, observing fluffy, powdery snows. Temperatures in these parts are well below freezing and even in most cases below 0ºF, adding to the fluff factor and allowing the snow to easily accumulate to anything and everything. Scattered snow coverage can be found further south into northwestern SD while warmer air working in south of there causing mixing concerns with freezing rain. This includes the Rapid City area. Expect snow coverage to expand eastward with time this afternoon while warm air intrusion on the south end of the snow axis allows for bouts of mixing and freezing rain…additional details later!
The areas of dense fog in portions of MN will remain pesky this afternoon and evening, though the greatest coverage should still shift southward into southern MN with time. Isolated pockets of freezing fog will also be possible across a corridor stretching west to east across central SD, but won’t be widespread. Progressing into tonight, the increasing low-level moisture and warmer air over the snowpack in southern MN will continue to linger fog risks until the storm system from the west finally kicks the threat out of the area Monday morning.
Not much in the way of changes can be noted with the weather bulletins in place across the area. We still note Winter Storm warnings for the northern two-thirds of ND into northwestern MN with Winter Weather Advisories positioned further south across the remainder of southern ND, the northern fourth of SD into northern MN. The threat for freezing rain allows for Winter Weather Advisories stretching from southwestern MN through the Minneapolis Metro area. Those under Winter Storm Warnings have the greatest chance for 6″+ of accumulating snow, especially with the high-ratios expected. Also, Dense Fog Advisories remain in place for southern and eastern MN.
Mesoscale analysis of the winter storm lifting through the Dakotas can tell us plenty about what is going on within the atmosphere. Take note of the hatched green areas along with the purple contour lines. The hatched green areas depict relative humidity within the snow growth layer to be greater than 90%. ND into northwestern MN have the greatest emphasis of higher saturation within this layer telling us that these are the areas to watch for heavier snows given the proper dynamics. Also, the purple contours (depicting rising motion) is greatest within northern ND and northwestern MN, suggesting greater frontogenesis within these zones. Putting these two variables together, you will find the heaviest axis for snow will be within the northern two-thirds of ND into northwestern MN with the forcing being less conducive further south.
Simulated radar through 9pm CST Monday: Snow coverage across the western two-thirds of ND and northwestern SD will continue to expand eastward through the remainder of the afternoon and evening hours, gradually lifting into northwestern MN over the next couple of hours. The snow in northwestern SD currently will transition to a mix of rain, snow, sleet and freezing rain at times in north-central SD as warmer air lifts into these parts through the afternoon, though should then transition back to snow showers into the evening. Precipitation in general should remain on the lighter side in SD with more mixing issues through the evening. However, as previously stated, scattered backside snow showers will become common overnight before dissipating across the state by 6am CST Monday. Moderate to heavy snows lifting into northwestern MN in the next couple of hours will continue their progression eastward through the evening and overnight while mixed precipitation such as sleet and freezing rain will be more common in the southern half of the state. Snow coverage will lessen with time in ND overnight and especially Monday morning, mostly pulling out of the state by the lunch hour. It will be at this point when most backside snow coverage will be remaining in northern MN. It’ll take some time for this system to lift out, continuing backside snow showers in northern MN Monday afternoon, then eventually just northeastern MN in the evening before lifting out around 9pm CST. Please note that breezy conditions will accompany this system as it pushes across the region, so lower visibilities along with blowing/drifting snow will be common. Travel conditions will be extremely difficult as the snows and freezing rain progresses across the region this afternoon into tonight.
Total snowfall forecast (including snow that has fallen already in portions of ND) through Monday evening: Even as the storm is unfolding, discrepancies in data regarding snowfall remain. Regardless, the map shown below is a solid ground for what to expect total snowfall-wise through the remainder of the day, tonight and into tomorrow. Confidence is still low south of the Bismarck and Fargo areas as some guidance suggests 6″+ of snow in these areas while others are more hesitant. This can even include cities such as Eureka, SD. However, given the best lift and snow growth zone development is positioned in the northern two-thirds of ND into northwestern MN, these areas have the highest likelihood of 6-12″+. There is the chance that the northern third of SD can overachieve, but the guidance that suggests it are limited. Localized pockets of 12-15″ remain possible in the northern third of ND and far northwestern MN. Essentially, the further north you are located in the Northern Plains, the greater snow amounts you should anticipate as atmospheric forcing will be greater. Mixed precipitation further south will hinder snowfall totals with many in the southern areas receiving little to no snow.
Freezing rain across portions of southwestern SD but especially southern MN will be common and is expected to lead to a light glaze of ice generally under 0.1″. Locations under the Winter Weather Advisory in southern MN stand the best chance to see these amounts. Definitely expect roads to be hazardous and slick in these areas as the freezing rain comes down. With the breezier conditions as well, gusting to 30mph at times, this will definitely pose a risk for some trees and power lines.
If you have any questions do not hesitate to reach out! Have a great rest of your day!