Every spring mobs of climbers head to Mt. Hood and other Cascade peaks to climb and ski on the great spring corn snow. It always seems that as the weather gets nicer, the number of climbers increases, and the risk of accidents does as well.

One of the great things about the Cascades is the relatively stable spring snowpack. But that's not always the case. Any rapid changes in weather or snow conditions can increase the avalanche danger dramatically. Large wet snow avalanches are not uncommon in the Cascades. I've never witnessed one in progress, but I've seen the aftermath and it's mind-blowing. Imagine a giant snowcat plowing walls of snow over 10- feet high on the side of a remote mountain, creating a path a hundred yards wide and several hundred yards long. I've seen this on North Sister in central Oregon and on undeveloped slopes of Mt. Hood. The paths from these wet snow slides are simply amazing. And sobering.

So, what to look out for? Steep slopes with a big exposure to sun. The warming can cause melting which can trigger wet slides. If you can find a safe, small slope to test for stability, that's always a good idea. And keep an eye out for natural slides. If the snow is moving on its own, it'll move a lot easier once a skier or climber adds his or her weight to it. Try to always watch and test the snow as you travel in the backcountry and change your route if you think it's even somewhat unsafe.
Wet snow avalanches sometimes move slowly, but that doesn't mean they are not dangerous. The snow can carry you into trees or terrain traps like cliffs or gullies.

The freezing level will rise to 12,000 ft Friday, higher than it's been all spring. The warming will increase the threat of wet snow slides Friday. Cooler weather Saturday should help stabilize the snow through Monday. But if the long range forecast charts are correct, beginning Tuesday we'll see an extended period of warm weather that may greatly increase the threat of wet snow avalanches. There's also a lot more snow to move this year compared to last year. As of April 15 there was 201" of snow at Timberline, more than twice the 88" that covered the ground at same time last year.

It'll be a great year for spring skiing and climbing! Remember to keep an eye on snow safety when you're in the mountains, so you don't end up on the evening news.

Matt Zaffino
KGW Chief Meteorologist

Posted by at 9:24 PM | Permalink

Just when you think we're settling into a springtime weather pattern Old Man Winter throws out one last shot. An unusually wet and cold storm is now brewing in the Gulf of Alaska. Look at the satellite map below.

As the storm gathers strength and continues moving south we'll start to see it late Thursday. At first increasing clouds will move in from the northwest, then rain develops by early Friday. Most of Friday will be wet, rain will transitions to showers by Saturday morning. The cold air arriving from the north will drive snow levels down well below pass levels, I wouldn't be surprised to see snow at 3000ft. Headed over the hills for this weekend could be a challenge, 1 to 3 feet (Yes I SAID FEET OF SNOW) is possible out of this system. This is great news for skiers! The problem is getting to an from the mountains studded snow tire were supposed to be off your car the first of the month.

I think Easter Sunday egg hunts and church services should stay indoors. By Sunday morning the GFS 500mb chart has us in a very cool and showery pattern.

Winds at 18,000ft over Portland will be around 70mph from the southwest. This is a good pattern for periods of heavy showers, followed by sun breaks then another round of showers.
We'll likely stay in this pattern through the middle part of next week, gradually warming and drying by next Wednesday.

Stay Tuned
Dave

Posted by at 10:01 AM | Permalink