DETROIT – Here is a timeline and how much ice to expect as freezing rain approaches Metro Detroit.
Local 4 has issued a 4Warn Weather alert for Thursday morning due to freezing rain and the potential for ice accumulation.
Freezing rain has to do with a temperature inversion in the upper atmosphere. Technically, it’s sandwiched between two layers that are below freezing. The clouds spit out snow, which falls into a layer that’s above freezing, so it melts.
Then, there’s not enough time as it reaches the colder layer at the surface for it to refreeze. If it did, it would be sleet.
So we’re looking at liquid precipitation that could become black ice, which forms when freezing rain -- which is liquid precipitation -- freezes on contact with a frozen surface.
It’s not actually black in color. It’s transparent, so it takes on the color of the surface below.
Timing of freezing rain
We’re going to see freezing rain lift north of the state line into Michigan just after midnight Wednesday into Thursday.
It will overspread the area during the pre-dawn hours, and most of it will be moving out by about 7-8 a.m. Thursday.
Temperatures will quickly slide as that warm front is chased by a cold front. We’ll reach about 40 degrees for a high Thursday, but temperatures will tumble throughout the day.
So the most impactful time of this weather is during the Thursday morning drive.
How much ice?
Ice accumulation totals are between a glaze to about one-tenth of an inch.
The higher amounts are closer to the state line.
It’s hard to pre-treat because this is still liquid precipitation, even though it results in ice accumulation.
There’s a chance it could cause power outages, but what we’re currently forecasting doesn’t really fit the threshold of power outages. You need about a half-inch of ice on power lines for it to be disruptive. If you factor in some gusty winds, you don’t need quite as much, and there are gusty winds in the forecast -- later in the day after all of the ice melts.
