The average person would look at the forecast this weekend and think it was a piece of cake… temperatures above average and a little light wintry mix possible. Done. It's that simple. But not so fast… this weekend's forecast is INCREDIBLY complex with high potential for inaccuracy because there are so many variables that just can't be measured. Let me show you just a little of what I'm talking about.
A little background first. The atmosphere acts like a fluid… everything is connected. That being said, there are still separate and very different air masses funneling across the surface of the earth. Not just east to west or north to south, but an air mass can change (and often does) with height as well (everything is 3 dimensional). Because of this, wind direction is a HUGE factor in forecasting. The direction of the wind in Minnesota could make it a cloudy day with temperatures in the 20's, or a sunny day with highs in the 60's. Without any other change, temperatures can vary that wildly entirely based on wind direction.
With that said, the last thing any meteorologist wants to see, especially this time of year, is a stationary front like the one that's overhead right now and can be seen in the image below. A stationary front marks the boundary of 2 different air masses.
This stationary front sitting over Minnesota Saturday will likely wobble in one direction or another because the atmosphere is constantly moving, so the boundary is getting pushed and pulled from one direction to another. Kind of like a string would move in a pool if someone jumped in. Everything affects everything else. So you have one very warm air mass to the southwest of the front, and a much cooler air mass to the northeast of the front. But this is just part of the story. The location of the stationary front on the map is just the surface location. Obviously air masses have depth to them or we wouldn't be able to breathe, so these travel up into the sky. The image below shows what the atmosphere looks like at about 5000 feet up.
On this map is the Upper Midwest with 3 different colored lines representing specific temperature lines. The blue is 10 degrees below zero in Celsius (14°F), the purple line is zero degrees Celsius (32°F), and the red line is 10 degrees Celsius (50°F). So from southwestern Minnesota into southern Canada (from arrow to arrow) or a little over 500 miles, the temperature at 5000 feet goes from around 0° to 60°. That's unreal!! Now with temperatures this warm just above the surface, the potential for the ground to warm is HUGE. BUT, there are limiting factors at the surface that could prevent significant warming. First, there is a large snow pack all around us which prevents warmer air from trekking north from Nebraska and Iowa because it has to cover a whole lot of very cold snow. See the current snow cover in the image below…