textproduct: Aberdeen

KEY MESSAGES

- Downslope winds of 25 to 30 mph tonight into Tuesday morning may produce drifting snow along the eastern side of the Sisseton Hills. At this time, the snow is not expected to be lofted high enough to reduce visibilities.

- There is a 40% of snow Wednesday morning over northeast SD and west central MN. Snow accumulations are expected to be less than an inch.

DISCUSSION

Issued at 1242 PM CST Mon Dec 29 2025

High pressure currently over southeastern SD has created a sunny sky across the area today. But even with that sunshine, the cold air that surged in yesterday is still keeping temperatures cold, with mid-day temps in the single digits above zero over northeast SD and in the mid teens towards Pierre. Those clear skies will be short lived, as there is an area of mid clouds dropping to the southeast across the northeastern two thirds of ND and will be moving into SD and west-central MN later this afternoon and through the evening hours. This is ahead of the first of two weak clipper systems moving through the region over the next couple of days.

Before getting into the clippers, did want to mention that there will likely be a weak downslope wind event on the east side of the Coteau tonight into Tuesday morning. Overall, it's not the best direction for winds (more westerly instead of southwesterly), but could see some enhancement in the winds and gusts getting up into the 25-30kt range. With the fresh snow in this area, that does bring up some concerns for blowing/drifting snow. This will depend on the sustained winds and with the age of the snow pack, we'll need sustained winds over 25kts to start seeing larger areas of lofted snow to reduce visibility. Right now, that's not expected and will continue to message the drifting snow (snow not being lofted more than a couple feet off the ground). As temperatures warm into Tuesday and towards freezing, that could lead to some roads becoming icy where drifting snow occurs.

Now for the clippers. The current northwesterly flow aloft will be fairly consistent over the next 5-7 days with a ridge over the west and a trough over the eastern CONUS. This will bring a couple clippers/shortwaves through the upper midwest on Tuesday and Wednesday. The first clipper will track from Winnipeg and through northern MN, putting the northeast edge of our CWA on the southwest side of the precipitation area. At this time, only highlighted a slight chance (15%) for snow over Traverse county for tomorrow morning. EC-Ens seems less enthused about the warm nose into west- central MN on Tuesday morning (less than 25% of members have warm nose above 0C) and the P-Type meteograms show a sub 5% chance of a mix. Thus, have left as snow for now, but will need to monitor for any potential mix, especially if the precip ends up being a little farther to the southwest than currently expected.

After this initial wave, we might see a brief clearing, then additional clouds move in ahead of the next clipper. With that shallow moisture, models are showing hints of light QPF Tuesday night in far northeast SD and west-central MN (more so in eastern ND and into central MN), which could also be a concern for mixed precip due to the dry air above -10C and limited ice present. Then the next clipper (weak 1016mb low tracking through western/central SD) arrives on Wednesday morning and continues into the first part of the afternoon. Best opportunity for snow appears to be over eastern ND and into northwestern and central MN with the northwest to southeast track. Forcing for this event will be associated with a narrow area of 925-850mb FGen. That of course leads to some uncertainty on the track of the band, but models do seem to be fairly consistent in this band being strongest in eastern ND and then brushing the far northeast part of SD and into west-central MN. NBM 25th-75th percentile snowfall amounts still show values being light (0-1"), mainly to the northeast of a line from Britton to Clear Lake. Winds still look to be light enough to not lead to any blowing/drifting issues.

For the rest of the period, no significant precipitation chances at this point. Temps will settle back closer to normal for the new year (although plenty of spread in the NBM 25th-75th percentile highs). With the northwest flow aloft, the coldest temps will be in northeast SD and warmest over the southwest. Finally, there are some hints of a stronger shortwave rounding the western ridge and moving through the region for the second half of the weekend. Right now, it appears any precip chances will remain to the north of the area and over northern ND/MN and southern Canada.

By 00Z Wednesday we'll be in between systems. Warmer air with 850mb temperatures of 0 to 4C will remain over central SD, with 0 to -7C degree air over northeastern SD and west central MN (lowest over MN). The contrast becomes greatest by late morning Wednesday, with surface temperatures showing the contrast with highs near 40 in Jones County, while in the teens over west central MN.

While flurries or very light precipitation will be possible Tuesday morning over our far northeastern counties (showing up on a couple of CAMs), the next chance of measurable precipitation looks to hold out until mainly Wednesday morning over northeastern SD and west central MN, in the form of a 40% chance of light snow. Snow to liquid ratios will be around 10-15:1. With a banded look, it will be difficult to pin point the exact location of highest precipitation/snowfall, but at this time it looks to focus on our west central MN counties with around 1" or less snow. There is around a 30-40% chance of 1" or more snow over that location, and a 15% chance of 2" or more snow. One thing we'll need to monitor is the potential for a wintry mix (freezing drizzle) from around 00-12Z Wednesday, as noted on the 12Z ENS precipitation type meteograms and backed by plenty of low level moisture below 800mb. It looks like snow is most likely, with most of the precipitation from 12-18Z.

Much of the rest of the forecast remains dry with temperatures moderating back into the 20s and 30s by Friday or Saturday and continuing through the weekend. Confidence in specific temperatures remains only moderate at this time given the average 10 degree spread in the NBM 25th-75th ranges starting Wednesday and continuing through the period.

AVIATION /18Z TAFS THROUGH 18Z TUESDAY/

Issued at 1123 AM CST Mon Dec 29 2025

Terminals KABR,KATY,KPIR,KMBG

VFR conditions will prevail at all sites. As an area of high pressure that is currently over the area moves to the southeast, winds will increase out of a westerly direction on Tuesday.

ABR WATCHES/WARNINGS/ADVISORIES

SD...None. MN...None.