Let's take a look at all the different types of precipitation we can see through winter and how they develop.
Most commonly, we think of snow and cold when we talk about winter weather, but winter weather can show itself in many ways! Let's look at the different set up we need to see different types of winter precipitation.
Just like the weather varies here at the ground level, where we live, the weather varies at different heights, or levels, in the atmosphere. When I do school talks, I sometimes talk about the atmosphere like a stack of pancakes. The bottom of the stack would be where we live, and each pancake above that is a different layer, going higher and higher into the atmosphere. As you get higher in the stack, each pancake is a little different, with more or less moisture, different temperatures, different wind directions, and so on. Envision those layers while looking at the graphic above.
Starting on the left, frozen precipitation (high in the atmosphere) falls through a large enough layer of warm air that it melts, and at the surface we see rain.
For freezing rain, frozen precipitation falls into a layer of warm air, causing it to melt. But then, near the surface, the rain encounters a shallow layer of cold air. That results in the rain freezing on contact with cold surfaces.
Sleet has gone through the process of melting, but falls through a thicker layer of cold air, meaning it has time to fully refreeze before hitting the ground.
When we have all snow, the temperature profile is consistently below freezing.
Lake Effect Snow
Living near the Great Lakes, we are familiar with lake effect snow. Here in southeast Wisconsin, we see lake effect snow less often than the other side of the lake, largely due to the predominant wind direction. Weather systems tend to move from west to east in the mid-latitudes (where we live) and therefore lake effect snow events more often impact areas east of the Great Lakes. But, when the setup is right, with an easterly wind component (and other necessary factors), we can see lake effect snow here.
When cold air moves over the relatively warmer waters of the Great Lakes, evaporation occurs, and heat and moisture are drawn up into the atmosphere. Clouds grow and begin to produce snow, which often falls in narrow, heavy bands over the nearby land.
Snow Squalls
A snow squall is a burst of intense snow and wind. These winter storms can cause a sharp drop in visibility, posing a major hazard for motorists. Whiteout conditions can trigger chain reaction accidents on roadways. The National Weather Service can issue Snow Squall Warnings when snow squalls are imminent or occurring. These can cause cell phone Wireless Emergency Alerts (WEAs) to active within the warning area. These warnings usually last between 30-60 minutes and are focused on a small area with the highest potential for impact.
Be sure you're ready for winter weather by checking out the other TMJ4 Weather Blog posts from this week. If you have a weather question, or an idea for a blog post, write to us at weatherteam@tmj4.com.