4Warn Weather – The National Weather Service is calling it an “Epic battle of air masses.” A clash between warm and cold that could result in a significant ice storm for much of Metro Detroit. A slight change in temperature in the first few thousand feet of the atmosphere can completely change the impact of this storm from minor to crippling.
And when I say slight, I mean one or two degrees. The difference between 30 and 32 degrees becomes critical when predicting an ice storm. We could have multiple types of precipitation Wednesday (Feb. 22), including rain, freezing rain, sleet, and snow. So understanding the vertical structure of temperatures in the atmosphere is key.
With ice, the atmosphere needs to be warm but cold at the surface. Our cold temps and breezy conditions Monday matter when it comes to what happens Wednesday. We will be paying close attention to road temps and surface temps Wednesday. Our lack of snow cover on the ground and, more importantly, the lack of ice on Lake Huron also influence the forecast.
With an easterly wind off the lake, we could get a push of warm air that would cause more rain than freezing rain for areas closest to the lake. A shift northeast and a small amount of cold air advection changes the forecast back to freezing rain.
Another frustrating part of forecasting ice storms is that computer models tend to overdo the amount of ice accumulation; This is where experience comes into play.
Skilled meteorologists look for patterns. Keeping data on previous storms can guide us during current, difficult-to-predict weather events.
Those of us that have been forecasting for over 20 years recall one of the most significant ice storms to impact Michigan on April 3 and 4, 2003. Ice accumulated from a half inch to an inch from the thumb down into Livingston, Oakland, and Macomb counties.
Over 450,000 people lost power, and the ice caused millions in damages.
One of my biggest concerns when it comes to ice storms is that people don’t understand the different types of precipitation. Many confuse freezing rain with sleet, and that can lead to a false sense of security when driving.
Freezing rain is not frozen as it’s falling. It comes down as rain and then freezes when it touches a cold surface. Unlike sleet that goes through a layer of warm air, then refreezes and falls as frozen precipitation.
Often times people see rain but don’t notice it is freezing on contact, so roads might look wet when in fact, there is a layer of ice. The same goes for driveways and sidewalks.
We will see rain, snow, sleet, and freezing rain on Wednesday. When it comes to ice, a tenth of an inch creates a glazing, a half inch or more, and the concern for widespread power outages and dangerous driving conditions grows significantly.
Wednesday is a 4Warn Weather Alert Day. We will be providing extensive coverage on Local 4 News, Local 4+, Click On Detroit, and the 4Warn Weather App.
More: ‘Travel could be nearly impossible’: Ice storm warning issued for parts of Metro Detroit
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