Weather Blog

It's raining marshmallows? No, it's just 'graupel'

It's raining marshmallows? No, it's just 'graupel'
Graupel in Fife by Todd O'Bannon

After all the "snow fireworks" Wednesday morning with the Convergence Zone bringing snow to the North Sound and Eastside, the fireworks became a bit more literal as thunderstorms popped up and struck Skagit County and south King County/greater Tacoma area.

We had several reports of lightning and near white-out conditions in Tacoma, Fife, Federal Way, Covington, Kent, and Auburn.

But perhaps the most amazing part of the cells was the "weird hail" that accumulated on the ground. It was like little mini snowballs -- described by one as "raining marshmallows" and another as "mini Styrofoam pellets that looks like the fake snow outside Santa's house at the mall."

That's called "graupel." It's basically a soft hail stone, caused when snowflakes fall through super-cooled raindrops (as in water that's gone below 32 degrees but hasn't frozen yet) and makes this cold rain freeze to the flake, turning it into more of a snow ball... or marshmallow....or... Styrofoam pellets.

Hail forms in somewhat the same way -- only it's ice at its core that takes on new coats of water from raindrops, which then freeze into an added layer of ice.

With hail, it's the storm's updrafts that push the stone back up to high levels of the atmosphere where it refreezes, falls toward the ground where it picks up more rain drops, then encounters the updrafts that push the stone back up for another go-round of picking up water and another ice layer.  The process repeats until the hail stone is heavier than the winds can support, and the stone fall to the ground. That's why large hail stones are associated with large thunderstorms -- it takes 55 mph updrafts to support golf-ball sized hail.

But graupel can accumulate and cause slick roads just like hail -- maybe even more so since the graupel is easily squished into an icy pancake when driven on.

Here are some other photos we received from the "Graupel storm":

From YouNews contributor Miltonwadude:
Next two of Tacoma, by Twitter user @awildcelticrose

And this great shot of lightning behind a snowy home in Auburn, by YouNews contributor robert3366