- Posts: 150
- Thank you received: 0
Late Spring/Summer Avalanche Hazard
- DG
- [DG]
- Topic Author
- Offline
- Junior Member
As a relative newbie to b/c skiing, I'm uber-cautious about avalanches to the point of probably missing some good snow. But that's okay - I'm frankly scared stiff of the thought.
So, I've mostly resigned myself to chasing powder inbounds off the lifts during the winter and waiting until at least May for any real backcountry skiing, after the snowpack has settled out (note: this year being exceptional, maybe June). That being said, it's still hard to find information on the potential risks for late season (late spring/early summer) avalanches, even though I know they can occur. Most of the training materials talk about winter conditions (I have admittedtly not taken a field class yet).
So, I'd like to pose the general question about late season skiing:
If one is to watch out for placing themselves on seasonal hazards like thin snow bridges and cornices, and resigns themselves to skiing after
(1) the snowpack has gone through several freeze/thaws, and is likely isothermic and well consolidated
(2) there has been no significant recent rainfall (or late season snow)
(3) there have been clear conditions overnight to let the snowpack freeze
(4) and you get an early start and turn around before the sun loosens the surface too much, beyond the prerequisite couple of inches for some good corn skiing,
Are you generally safe to target steep slopes assuming the main threat is from solar warming of the surface? Or are there other avalanche hazards to look out for this time of year?
This is of course acknowledging the usual disclaimers that b/c skiing is unsafe and you can never know for sure - I'm just trying to get a better idea of what to look out for during the late season.
Thanks!
Please Log in or Create an account to join the conversation.
- Skip E.
- [Skip E]
- Offline
- New Member
- Posts: 7
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- Skip E.
- [Skip E]
- Offline
- New Member
- Posts: 7
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- garyabrill
- [garyabrill]
- Offline
- Senior Member
- Posts: 464
- Thank you received: 0
Probably in the spring to very early summer consolidation is the key. There are usually weak layers if there have been recent snows and if the trend is a warming one. That could be right after a storm or it could be a week or more after a storm if temperatures get too warm.
Most spring avalanche cycles are diurnal so how good the freeze is makes a big difference. During prolonged warming periods, however, older weak layers periodically rear their heads (as Skip pointed out).
The most effective observations include depth of ski or foot penetration, how good the overnight freeze is and surface roughness. If there are meltwater channels showing on the surface or if you see red algae or suncupping it may well be past the time of significant avalanching.
Please Log in or Create an account to join the conversation.
- skierguitarist
- [skierguitarist]
- Offline
- Junior Member
- Posts: 64
- Thank you received: 0
Those are great books to read for sure which I go through once in awhile. I like to learn about the newest insights so as to add to my additional arsenal of information.
Please Log in or Create an account to join the conversation.
- Gary Vogt
- [vogtski]
- Offline
- Premium Member
- Posts: 511
- Thank you received: 8
When I was a winter volunteer at Paradise back in the 70's, the weather data was not yet automated, so we had to phone the info to NWAC each morning. I noticed a fairly strong correlation between the 20-cm snow temperature and wet slide activity in the Spring. When the morning snow temps were cooler than about -5*C, slides tended to be uncommon, unless the Seattle high hit say 70*F after weeks of 40's & 50's. The closer the morning snow temp was to zero, the higher the frequency of wet slides in early to mid-afternoon.
This is just one factor among many, of course, but consider carrying a dial stem thermometer to help quantify your decision-making process. You might have to adjust the numbers a bit for elevations & aspects other than the 5-7K sunny slopes around Paradise.
Please Log in or Create an account to join the conversation.
- DG
- [DG]
- Topic Author
- Offline
- Junior Member
- Posts: 150
- Thank you received: 0
A question on the snow temps - what is the best method to measure these? Would you push the thermometer down into the snow overnight, and then take the reading in the morning? Does 20 cm refer to the depth of the measurement?
Cheers,
David
Please Log in or Create an account to join the conversation.
- Lowell_Skoog
- [Lowell_Skoog]
- Offline
- Platinum Member
- Posts: 1460
- Thank you received: 16
The key exception I can think of is when the snowpack is not really isothermal yet (generally earlier in the spring). In this case, you may have a good supportive crust after a cold night, yet there can be weak layers persisting underneath. One time I observed this was during a tour from Rainy Pass to Heather Pass (North Cascades highway) several years ago. As I was climbing the south facing slopes toward Heather Pass on a supportive crust, the slope started whumping. Spooky! I moved to the colder north facing slopes on the other side of Lake Ann and enjoyed good skiing on that side. It was powdery there as I recall.
Please Log in or Create an account to join the conversation.
- Gary Vogt
- [vogtski]
- Offline
- Premium Member
- Posts: 511
- Thank you received: 8
As for your questions about the thermometer: yes, the 20-cm refers to the depth & it takes only a few minutes to get an accurate reading. Life Link includes these in their snow pit kits, but they seem spendy to me. (Anybody know a cheaper source?) I'd recommend attaching a bit a bright flagging so you don't lose or step on it while skinning up/ getting ready. They're pointy & fragile, but you can make a nice sheath from a scrap of plastic pipe.
If I remember correctly, a reading of 0*C means the snow is saturated with free water. With a high reading at the start of the tour, you'd probably want to adjust your plan, especially if you're doing a loop or traverse where it's more difficult to just back off if the snow starts to change quickly.
"Uber-cautious" is OK, after all, it's your game-your rules. IMHO, risk is relative, and most people, on most days, are at greater risk driving to & from the snow than playing on it. Good luck & Happy Trails!
Please Log in or Create an account to join the conversation.
- ~Link~
- [Link]
- Offline
- Junior Member
- Posts: 124
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- jd
- [jd]
- Offline
- New Member
- Posts: 21
- Thank you received: 0
By the way, doubt many folks will be under that one very soon. The road is still gated and covered with snow, so you have 6 miles of road to get to the trailhead.
Please Log in or Create an account to join the conversation.
- peteyboy
- [peteyboy]
- Offline
- Junior Member
- Posts: 162
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- Scotsman
- [Scotsman]
- Offline
- Platinum Member
- Posts: 2432
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- Stugie
- [stugelmeyer]
- Offline
- Senior Member
- Posts: 291
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- garyabrill
- [garyabrill]
- Offline
- Senior Member
- Posts: 464
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- James Wells
- [Travertine]
- Offline
- Junior Member
- Posts: 217
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- Snodger
- [Snodger]
- Offline
- New Member
- Posts: 40
- Thank you received: 0
I seem to remember some early season concern that the ugly snowpack we were getting (weak layers buried under copious new heavy snow) at the time would end up being a problem come spring.
As I was cruising up a slope where a huge cornice bomb had previously impacted I was trying to imagine the that slope releasing and stepping down to a deeply buried layer- it boggles the mind to think it could rip down deep in what seemed to be a fairly consolidated pack. but i guess if it's a couple feet of consolidated snow that would be a great slab if there was still some of those crappy layers beneath.
Anyone care to comment?
Please Log in or Create an account to join the conversation.
- Lowell_Skoog
- [Lowell_Skoog]
- Offline
- Platinum Member
- Posts: 1460
- Thank you received: 16
I seem to remember some early season concern that the ugly snowpack we were getting (weak layers buried under copious new heavy snow) at the time would end up being a problem come spring.
Here's a link to last January's discussion about potential spring hazard. I let my imagination run wild regarding the worst-case scenario for spring avalanches here . I don't know if you'd call this week's situation worst-case, but it is interesting.
Please Log in or Create an account to join the conversation.
- Lowell_Skoog
- [Lowell_Skoog]
- Offline
- Platinum Member
- Posts: 1460
- Thank you received: 16
Gary or others, in consideration of Gary's ominous forecast, do you have advice that is specific to the Easton Glacier route on Baker? We have a planned trip where we are expecting to set out from camp somewhere above 6k at about midnight Saturday with a target summit time of between 6 and 7 AM Saturday.
I won't predict whether you could ski the Easton Glacier safely on Sat-Sun. I'm reluctant to offer that advice here.
But I'm certain that if you'd like to climb and ski Mt Baker with good corn snow, it would be better to go later in the spring.
Please Log in or Create an account to join the conversation.
- RonL
- [RonL]
- Offline
- Senior Member
- Posts: 259
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- juan
- [jon_ambrose]
- Offline
- Junior Member
- Posts: 134
- Thank you received: 0
Here's a link to last January's discussion about potential spring hazard. I let my imagination run wild regarding the worst-case scenario for spring avalanches here . I don't know if you'd call this week's situation worst-case, but it is interesting.
I'd guess those predictions you made last January may prove rather accurate. may be a good wknd for other outdoor activities.
Please Log in or Create an account to join the conversation.
- James Wells
- [Travertine]
- Offline
- Junior Member
- Posts: 217
- Thank you received: 0
I'd guess those predictions you made last January may prove rather accurate. may be a good wknd for other outdoor activities.
Looks like they were spot on. From NWAC:
This upcoming hot weather is expected to cause a widespread
spring avalanche cycle in most areas starting Thursday. The
relatively prolonged hot weather should melt and weaken
significant near surface snow and allow melt water to possibly
percolate to deeper older weak layers. This is most likely on
slopes facing the sun but should also be likely on any steep
aspects. Deep avalanches are possible. Some slides may release
to or near the ground, involving the entire winter’s snowpack.
The expected large wet snow avalanches may travel very fast
and run long distances, possibly to lower elevations where
little or no snow cover may remain or to valley floors.
We do not recommend back country travel near any avalanche
terrain Thursday and Friday and possibly through the weekend.
Initially small wet loose avalanches may trigger large and
deeper wet loose or wet slab avalanches. Back country
travelers should also avoid slopes below cornices or gullies
and flat areas below avalanche run out zones. A lack of
refreezing at night may contribute to the avalanche cycle.
Remember that boot or ski penetration of more than a few
inches can indicate snow is becoming significantly unstable on
steep slopes.
Please Log in or Create an account to join the conversation.
- garyabrill
- [garyabrill]
- Offline
- Senior Member
- Posts: 464
- Thank you received: 0
The snowpack is not nearly as well consolidated as usual for this time of year and now comes record or near record high temperatures, so I would think looking at this before it happens, it should be pretty much a worse case scenario. In my recollection I don't recall such a dramatic shift from persistent cool early and mid-spring conditions to such dramatic and intense heating. Whether or not and how frequently the slides go to the deeper snowpack (February - at least, remember it didn't snow much for 5-6 weeks so the pack consolidated then) is anybody's guess, but some of the slides should involve much of spring's snows. The slides could be slabs, but even wet loose slides in this situation are a major concern because of the probability of a lot of entrainment. The other really bad layer is the early December layer.
East of the crest the snowpack is weaker, in some areas down to the ground. I was surprised in March to find heavily faceted snow at the base of Blewett Pass's snowpack. The faceting was much more pronounced than normal, despite more than average winter cloudiness. So, in areas east of the crest without deep snowpack, it wouldn't be surprising to see those slides go to the ground.
Current models now show a pretty good drop in the freezing level Tuesday but possibly warmer weather again late next week. It will take more than a day or so of cooler weather to help stabilize things after this dramatic ramp up in temperatures.
Please Log in or Create an account to join the conversation.
- Pete A
- [Bud]
- Offline
- Senior Member
- Posts: 431
- Thank you received: 0
...this is second hand info but i figured i'd post it anyways.... a friend of mine who was just up high on Rainier over the past few days trying to get in a climb described conditions on the upper mountain as 'waist deep wallowing' and said the glaciers haven't been refreezing at night.
I really wanted to ski Rainier this weekend...but gonna opt for some quality time on my surfboard instead.
Please Log in or Create an account to join the conversation.
- Garth_Ferber
- [Garth_Ferber]
- Offline
- Junior Member
- Posts: 79
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- Eli3
- [Eli3]
- Offline
- Junior Member
- Posts: 69
- Thank you received: 0
Please Log in or Create an account to join the conversation.
- garyabrill
- [garyabrill]
- Offline
- Senior Member
- Posts: 464
- Thank you received: 0
holy crapballs at blackcomb!
www.tetongravity.com/forums/showthread.php?t=123577
It sure shows that the cycle was a widespread one and worse in areas that were colder in early December. It's noteworthy that many of the slides broke out in shallower areas - a sign of faceted snow or depth hoar.
A couple of the Whistler slides Lee Lau posted were amazing for the width of propagation, which speaks to the weakness of the basal layer. One of them even crossed two major ridgelines!
With poor freezes due to lack of clear skies and a rebound in the freezing level on the weekend some more stuff may well rip out given the "success" avalanches had last weekend.
Please Log in or Create an account to join the conversation.