Snow Totals For One Storm...Getting Ready For the Next
by Angela Schilling, Meteorologist
January 21, 2012 8:21 PM
It’s been an active last couple of days and Sunday looks to be the same especially in the morning. Friday’s storm brought anywhere between 2 to 5 inches in eastern South Dakota, and up to 7 inches in northwest Iowa. Temperatures will remain at or below freezing for quite some time, so the snow is going to stick around for a while. Heading into Sunday morning some of us could see a little bit of freezing rain, sleet, and light snow. The image to your left is from Saturday afternoon along I-29 just north of Sioux Falls, and is a great example of the blowing and drifting snow we experienced this weekend.
Sioux Falls received its first one-inch snowfall just this past Tuesday and now we have 4 and half inches to add to the grand total. The majority of the snow fell east of the James and south of Highway 14. Spencer tops the list with 7 inches total. Notice on the table below how Chamberlain only received 2.2 inches, and the east got twice as much.
On Sunday the snow is not going to be as straight forward. Warm front is going to swing through the region beginning Saturday night bringing in warmer air to the region. So we’ll have warm air aloft and cold air at the surface. The precipitation will start out as a rain snow mix in the northeast before transitioning all over to light snow. In the southeast we could get a little bit of freezing drizzle early Sunday morning with a light dusting of snow towards the later half of the day. Accumulations will be light with ice picking up less than a hundredth of an inch and around 1 to 2 inches of snow in the northeast. The first image below is for Sunday morning at 850mb or just above the surface, and the second image is at the surface. Notice how we’re just a tad warmer in the first image than the second. In order to get freezing rain you have to have warm air above cold air which is at or below freezing. Of course when you forecast precipitation type it becomes more complicated, but in general you need a deep melting layer (a layer with temperatures above freezing) or your warmest temperature aloft to be at or above 3.4 degrees Celsius, in order for you to get freezing rain opposed to say sleet or snow. However, if you have warmer air aloft with freezing temperatures at the surface, but either your melting layer is shallow or your warmest temperature is colder than 3.4 degrees Celsius you would get sleet. Snow forms with basically no melting layer aloft.
*850mb, just above the surface...with temperatures around 30 degrees
At the surface with temperatures below freezing
Besides temperatures, the amount of moisture also plays a role with Sunday's weather. Notice on the 850mb image above how the bulk of warm air is to the southeast, which is also where the dry air is. Since the Sioux Empire is lacking in moisture we'll probably just see freezing drizzle opposed to a little bit of freezing rain.