Storm Center PM Update – Friday, December 27: Winter Storm Warning


It has been an unusually mild day across KELOLAND – fairly typical for the day before a big storm. With mostly lllsunny skies temperatures have risen through the 20s in northern KELOLAND, to the 30s or even low 40s in the south.

A Winter Storm Warning is in effect from tonight – especially late tonight – into Monday morning as a storm system comes in from Colorado. The warning is posted for most of KELOLAND except for Rapid City and the west – where amounts of snowfall will be less than we will see in central and NE South Dakota. Sioux Falls and SE KELOLAND are under a Winter Weather Advisory, because the weekend is likely to start with significant rain, freezing, and icing, followed by snowfall as strong winds cool the area down late in the weekend with snowfall on top of the ice.

Here in the Storm Center we are projecting some significant snowfall totals. Many areas north and west of Sioux Falls could see a foot or more of snowfall from this wet, slow-moving winter storm.

Here is the way the winter storm should develop: Tonight we will see rain coming in from the south, mainly after midnight. Temperatures will cool enough that we could see a mix of rain and snow out of this first burst of energy. There could be some small accumulations of snow by sunrise in central into portions of eastern KELOLAND. Lows will be in the teens in the north to the 20s in the south.

Tomorrow we will see rain or freezing rain and probably some coatings of ice in Sioux Falls and SE KELOLAND. The rest of KELOLAND will see snowfall, and it could really start to add up. There could also be a mixture of freezing rain with that heavy snow in central and NE South Dakota. Highs on Saturday will be a few degrees either side of freezing. Fortunately the winds will be fairly tame in eastern KELOLAND, though NW winds will be strong in western South Dakota.

On Sunday, Sioux Falls and SE South Dakota will see a mix of rain and snow as the winds pick up speed. We do have some concerns about that if we will have a coating of ice on the roads, trees, and maybe even powerlines. The remainder of KELOLAND will see significant amounts of snowfall as snowfall rates pick up, and northerly winds become strong. We remain concerned that there will be blizzard conditions in central and NE South Dakota, because winds could be blowing at 30-40 mph with higher gusts. Sioux Falls will see a changeover to all-snow on Sunday into Monday as the colder air comes in.

Monday we will see the system slow down a bit in intensity, though we still expect to have some snow falling during the day, especially the early part of the day. But we expect that very strong northerly winds will continue to blow, so blowing snow might be an issue. The snow that comes down will be of the wet, heavy variety, and the weight of those flakes may limit the blowing snow potential somewhat.

Skies will be partly to mostly sunny for New Year’s Eve (Tuesday), with highs in the teens to low 20s in central and eastern KELOLAND, while Rapid City recovers to the 30s. Temperatures should be a little warmer, near or above-normal, from Wednesday (New Year’s Day) through the end of the workweek – although if there is a thick snowpack from weekend snow, that could hold back our attempts to warm back up.

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