All eyes will be on a major December storm system taking aim at KELOLAND. Numerous warnings and advisories have been posted. Here are some of the highlights.
***Blizzard warning for much of western SD starting tonight for heavy snow, wind gusts over 40 mph, and white-out conditions with heavy snow
***Winter storm warning central and northern SD. Heavy snow likely, with some locations over 18″ by the end of the week.
***Ice storm warning starting tonight for northeast SD including Watertown and Sisseton.
***Winter storm watch for SW MN due to ice potential and strong winds, combined with sleet and snow.
***Winter weather advisory for Sioux Falls with a band of mixed precipitation overnight, including freezing rain.
We’ll begin by looking a big picture. A significant low pressure system will develop into Nebraska the next 24 hours. As we have stated with our previous forecast, this storm will stall to our south into midweek, creating a long window of stormy weather in KELOLAND. We’ll break down the details in the discussion below, but it’s important to remember this storm system will still be affecting parts of the region through at least Friday.
Take a look at our Hour-by-Hour forecast. There will be pockets of drizzle or freezing drizzle developing today as moisture increases on steady southeast winds. We expect a rapid increase of precipitation on radar this evening as rain, freezing, sleet, and snow develop. Keep in mind this first batch of moisture from Nebraska may contain some lightning and thunder. We expect additional rounds of mix precipitation tomorrow East River, with snow the dominate mode of moisture West River, transitioning slowly eastward over time.
I like to acknowledge wild cards in a complicated forecast such as this one. Lightning is on the table both tonight and tomorrow for the areas shaded in yellow on the map below. It doesn’t take more than a strike or two to ramp up the snowfall rates, so keep that in the back of your mind as you watch the radar tonight.
We are also dealing with a solid snow pack over southeast KELOLAND from last Thursday’s system. This could be enough to affect the rain vs. freezing rain scenario and we expect better details to unfold on this during the day.
Thus, the icing the next 24 hours is still a developing forecast. The best chances of ice will be north of Sioux Falls, but we will careful monitor the temperature forecast as a 1 or 2 degree difference will be enough to change the placement of the freezing rain.
The storm will be plenty of wind. The blizzard in the west will be due to the strong north winds. Sioux Falls and the east will experience strong east or southeast winds the next 24 to 36 hours. Any ice accumulation will be a problem due to the wind outlook.
There will be no shortage of heavy snow on this storm. You can see the timeline on the snow accumulation map below. First, expect the heaviest snow in central SD, with amounts well over 1 foot by Thursday. Sioux Falls will be quite different. In fact, Sioux Falls will likely see better chances of snow starting Thursday into Friday, so we still have plenty of time to examine how that will come together. Be prepared to roads to be closed as travel will become impossible in some areas.
If you prefer probability forecasts, the odds of 6″ of snow with this storm are pretty good NW of Sioux Falls.
The chances of 12 inches are rarely predicted this high on the European model. Numbers like these increase our confidence in a high impact storm.
Of course, the good news, we are getting some big help with drought pattern we’ve had. We’ll bank some of this moisture for the spring. There’s a lot more winter ahead.
Don’t forecast, arctic air IS coming and it will be very significant. Temperature may drop 30 degrees below normal before Christmas. That means lows AND highs below zero are possible for a segment of time next week. More details will come out on this story in the days ahead.
Here are the details of the forecast.