Weather Blog

Rain, snow and... falling ''dipping dots''?

Rain, snow and... falling ''dipping dots''?
Photo of graupel in Port Angeles on Feb. 26, 2012, courtesy of Colin Bradley

Some areas saw rain Sunday while others had a honest-to-goodness snow.

Then there were those that had none of the above -- but *something* was falling from the sky.

"The snow was more like round puffy snow or as my wife called them it, 'dippin dots,' " said Pete Matsudaira of Sammamish.

Colin Bradley of Port Angeles could attest to the same. In fact, he grabbed his camera, a ruler and some spare change to help highlight the strange precipitation that sort of looked like hail, but was soft to the touch.

But it's no mystery. That's just "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.

Anyway, here are some more photos, courtesy of Bradley: