The west end of the Columbia River Gorge saw freezing rain during this weekend’s event, but once you got around Multnomah Falls there was a transition to snow. This is very common with cold airmasses in the Gorge…coldest east of the Cascades and thinning rapidly west of Cascade Locks. In this transition area, the cold air in the lowest elevations wasn’t quite deep enough to keep the snowflakes together up around 2,000-3,000′ or so. So the snowflakes melted into raindrops. Those raindrops then fell into the cold air stuck in the Gorge; but in this case it was so deep the drops had a chance to freeze into ice pellets before they hit the ground. This is also sometimes called sleet, although the official definition is ice pellets. I have also heard it called “tapioca snow” by road crews in that area in the past. First time I heard that was 22 years ago…I’m getting old.
Anyway, this was one of those times where quite a bit fell between Bridal Veil and Bonneville Dam. In past cases I have seen it occur in the same area. These ice pellets easy bounce, slide, and roll down steep hillsides so they will form drifts (but not from wind) in gullies and other locations. If they are deep enough, a plow can’t handle it and ODOT has to call in a snow blower. That happened today near Multnomah Falls:
In 1996, when we had two back to back severe ice storms in the Gorge (2 days apart), the ice pellet drifts were massive, 10-20 feet high and blocked the old highway for many days. There was very little snow, just ice pellets and freezing rain. Here’s a picture of my (soon to be) wife standing in front of one…wow, 18 years ago in late December or early January that year. This was just west of Multnomah Falls:
She didn’t approve me using this picture, but it’s okay, she doesn’t read the blog anyway. Shhh! Plus I don’t have any other pictures of the drifts.
Chief Meteorologist Mark Nelsen