An avalanche at the Palisades Tahoe resort yesterday left wreckage in its wake, killing one person and leaving others with non-life threatening injuries. More heavy snow is on the way; forecasts say the risk of avalanches in the area remains “considerable,”
The avalanche comes amid a rash of storms that have brought more snowfall to California. Right now, California is at 42% of average snowpack statewide — a number that jumped up from 37% just yesterday, and much higher than the 25% reported at the Jan. 2 snow survey.
But these storms alone aren’t enough to get the state’s snowpack to a healthy level. So far, the year has been relatively dry, especially when compared to last year’s extraordinarily wet winter.
Andrew Schwartz, lead scientist of UC Berkeley’s Central Sierra Snow Lab, spoke with Insight’s Vicki Gonzalez and at a Thursday press event about snow conditions since the avalanche and what they mean for statewide snowpack.
This interview has been edited for length and clarity.
Interview Highlights
Over the past 48 hours or so, what have conditions been like for you?
Well, it started off relatively tame. About two days ago, we had a little bit of snowfall. Temperatures were starting to fall.
But over the last 24 hours is where it really ramped up. About this time yesterday, we were starting to get heavier snowfall rates, wind speeds were really starting to peak. We were seeing a lot of very high wind speeds, blowing snow around and over the last 24 hours, we've had about 10 inches of snow here at the lab, about 13 inches total over the last two days. So it's been a snowy one for sure
About 24 hours ago is when that avalanche took place. Can you take us back to what the Tahoe area was experiencing at this time?
Absolutely. At this time, we actually had some of our heavier snowfall rates starting to move into the area from north of I-80, basically. They were finally starting to move this way. We were starting to see our rates pick up and at the same time … those winds were kind of coming from a northwesterly area so that they were basically going out to the east.
And when we talk about the Sierra, the reason why we have drier areas on the east side is because we have that rain shadow — because when that wind pushes the snow into the top of the peaks, it tends to fall on the west side and then the dry east side stays dry. So as this was occurring, we were getting a lot of blowing snow up and over the ridges.
A lot of very strong winds, which can do things like wind load our snow, can be potential avalanche factors as well. So it was very stormy, very windy, and kind of difficult conditions to be out in.
So basically, the eastern slope of the Sierra can be more prone to avalanches if the conditions are right in regards to wind and snow?
If the conditions are right, yeah. It depends a lot on wind direction, but we see, oftentimes, wind loading. That's basically where wind will deposit a lot of snow in one area, typically over a ridge or on [the] opposite side of trees or things like that. It doesn't always necessarily have to happen on the east side, but in these conditions, that's probably where it was highest.
What do predictions ahead of avalanches typically look like? And what are the signs teams look for when trying to identify avalanche risk?
Forecasting is going to be based off of observations. Really getting to whether or not we have avalanche conditions is based primarily on teams going out into the field, digging snow pits and actually doing observations of whether or not there are weak layers in the snowpack.
When we talk about the potential for future avalanches, we can look at that based off of weather forecasts. I would say realistically speaking, a maximum of seven days, because we can identify things like temperature periods and calm periods that may allow for weak layers to develop … beyond that, it’s a little difficult.
I don’t necessarily want to speculate as far as what made yesterday’s avalanche happen … [but] typically speaking, when we get a slow start to the year as far as our snowpack is concerned, that can occasionally allow for weak layers to develop in the snowpack. So, when we have periods where we might get precipitation and then we might get a melting on the top that develops kind of a crust and then we do have additional snowfall that falls on top of that crust, that can present issues as far as creating a persistent weak layer.
It’s hard to say exactly what led to the conditions that caused the avalanche yesterday … but the late start to the season that we’ve had and the lower than average snowpack conditions certainly didn’t help.
In addition to avalanches, what other dangers have built up or can build up when storms like this take place? I know there’s limited visibility on I-80 now, too.
In addition to what you mentioned, kind of just travel and and being out in avalanche-style conditions. The big thing here with recent storms has been our wind chills.
When we talk about these very strong winds and the fact that these last couple storms have been colder than average, we can see wind chills that might be around zero or even below zero on some of these ridges and crests where it can only take a few minutes for frostbite to form on exposed skin.
So that's one of the issues. But of course, the big thing is when you're out trying to travel in these conditions, whether that be on foot or or in your car, there's a reason the National Weather Service typically tells you to stay home when we're expecting these big storms because if you end up getting yourself stuck in any way or getting into a problematic situation, it becomes much more dire if you're not well equipped with things like blankets and warm clothing and the emergency necessities.
In December, we saw lackluster snowpack levels of about a third of average. Several weeks and storms later, where do things stand today?
We're sitting better. I don't want to just keep harping on doom, doom, doom as far as our snowpack. We are doing better since the first of the year. We've seen our snowpack over double compared to what it was, and that's fantastic news.
Right now at the snow lab, we're at 53% of our average snow water equivalent, which is up from about 30%. Statewide, we're at 37% of average, so we are better. One of the problems, though, is that we started the year so dry that the storms that are coming in are just kind of keeping us roughly where we're at.
So if we're talking 40 to 50% of average, these storms are kind of just keeping us in that area. They're not really pulling us out and getting us closer to average at all. We really need something with three, four, five feet — you know, back to back big storms to really start making up for that lack of snow that we had early in the season.
So have we been getting snow? Yes, and that's a great thing because we're not becoming even more dry by not getting it, but we're not necessarily making up ground either.
You mentioned in a previous interview that these colder systems in terms of snowfall were really kind of heading more north, like northern California to the Pacific Northwest. Is that still the case?
That is, yeah. We see most of our snowfall occur in the northern part of the state and that's being reflected in our snowpack too. For instance, in the Northern Sierra and up to the Oregon border, we're about 40% of our average snowpack to date.
Here in the Central Sierra, we're about 38%. Down south, they're hurting a lot more than we are. They're at 29%. So those storm systems are going further up north right now. We are catching the southern edge of them, and we've been seeing a little bit more than we did earlier in the season. But so far, yeah, we're not sitting directly in the line of fire like we were last year when we were at 223% of average for this date.
