MARQUETTE, MI - Michigan has a lot of weather weirdness, and some of it has been falling from the sky yesterday and today over parts of the Upper Peninsula.
MLive Chief Meteorologist Mark Torregrossa prepared us yesterday that snow was in the forecast for our northern reaches with this week's cold snap. But when those snowflakes formed over parts of the U.P. yesterday and even this morning, they looked more like tiny snowballs by the time they reached the ground.
Welcome to graupel season.
What does that mean? Graupel is a snowflake that has extra "rime" on it - freezing water that collects on it after passing through a supercooled cloud. It freezes and bulks up the snowflake to look like a little snowball.
The National Weather Service meteorologists in Marquette reported graupel falling on the ground on Monday evening:
"A heavy shower brought a brief graupel accumulation to our office just before 7 p.m. tonight. Graupel is a "rimed" snowflake! Temperatures aloft are cold enough to produce snow, but as a snowflake descends to the ground it encounters a layer of supercooled water (still a liquid below the freezing point) which freezes onto the snowflake before hitting the ground. Graupel is not uncommon to see in the early lake effect season."
And more graupel was reported there this morning: "Is it winter yet!?! We've had a couple graupel showers this morning here at our forecast office. Expect scattered showers of graupel/snow and rain downwind of Lake Superior this morning before becoming scattered rain showers this afternoon."
Not to be confused with hail or sleet, graupel is in a classification all its own.
Torregrossa has explained graupel this way: "Graupel looks like tiny snowballs, and is different from hail and sleet. Graupel forms when falling snowflakes collide with raindrops. The snowflakes get sticky and stick together in a clump of snowflakes. The falling motion rounds off the flakes, and makes a tiny, slightly bouncy snowball."
This week's graupel season will be short-lived. A warming trend is forecast for later this week, with above-normal temps expected for the weekend.