Lowell_Skoog Posted November 14, 2000 Share Posted November 14, 2000 I received a flyer from the Friends of the Northwest Weather and Avalanche Center (NWAC) about two Fall 2000 benefit programs for the Center. They'll be showing TGR's new film "Further" at the following locations: Nov 16 at the Mountaineers Clubhouse, Seattle, 7:30 pm (Tickets available at Mountaineers bookstore) Dec 8 at Seattle REI, 7 pm (Tickets available at REI Customer Service counter) Cost: $7 general public $5 for Mountaineers or REI members For more information about the Friends, visit their website at http://www.avalanchenw.org. For more information about the Center, visit their website at http://www.nwac.noaa.gov. Quote Link to comment Share on other sites More sharing options...
Lowell_Skoog Posted November 14, 2000 Author Share Posted November 14, 2000 To stimulate interest in the topic of avalanches, here's a puzzler. I don't claim to have the right answer, but I have a theory or two... *** The current weather and snow conditions in the Cascades are setting the stage for significant future avalanche hazard. In which areas and under what conditions will this hazard be the worst? What changes in the current conditions could prevent the hazard from materializing? Post your guesses here! *** Quote Link to comment Share on other sites More sharing options...
Peter_Baer Posted November 14, 2000 Share Posted November 14, 2000 FWIW, snowshoeing above Snow Lake this weekend I saw what (to me) looked like evidence of at least two decent-sized slab avalanches on the E slopes of Chair and Roosevelt. I would have thought that with the fairly uniform, dry powder we have right now, we'd be seeing almost exclusively sluff avalanches (many tracks of which I also saw, BTW)? Is it possible for depth hoar to have formed in such a short time, what with the clear cold weather recently? Quote Link to comment Share on other sites More sharing options...
mikeadam Posted November 14, 2000 Share Posted November 14, 2000 ## [This message has been edited by mikeadam (edited 05-14-2001).] Quote Link to comment Share on other sites More sharing options...
gapertimmy Posted November 14, 2000 Share Posted November 14, 2000 I think Alex is on the money with his post. I'm no expert either, but reading his analysis gave me some shivers! Speaking of shivers, it looks like this cold patern is holding for some time, so these conditions might get even worse  Quote Link to comment Share on other sites More sharing options...
Alex Posted November 15, 2000 Share Posted November 15, 2000 Guys, I'm certainly no expert. I'm just going off what I seem to see in the Rockies every year - that is to say, my familiarity with temperate snowpack, and the real FEAR it instills in me, is probably biasing my assessment. Would be nice to have some paralax..? As to depth hoar, I thought about that too, but to be honest I don't know if its an issue or not - it is warm ground followed by cold precip or cold ground followed by cold preceip that would result in ground layer hoar? Actually, we currently have 2 significant precipitation events...certainly the snowfal Dan Smith, Nick and I ran into at about 6000 ft a few weeks ago is the base layer. This was also light snow, not as light as the next layer, which fell about a week ago now or more, and to much lower elevations. How will the 2 layers interact? My guess is that they are both good sliding layers, especially if the next cycle is triggered by heavy wet snowfall (a warm front with lots of precip - a Southwesterly flow). Alex  Quote Link to comment Share on other sites More sharing options...
Alex Posted November 15, 2000 Share Posted November 15, 2000 The clear and cold conditions, with sunshine and light fluffy snow on the ground, are certainly much more like the drier ranges (Rockies) than the maritime conditions we usually experience (warm, wet). I was surprised by the lightness of the snow last weekend even at low elevations, it is very unlike the PNW, a very temperate snowpack thus far. This is significant, as the light (in water content, weight) snow on the ground now (about a foot at 3500 ft, more higher) will be a weak layer if it gets loaded by heavier snow in the short term. Not only that, but the clear conditions and sunshine also lead to surface hoar on that layer, making for better layer lubrication if and when new snow is deposited. The continued cold temps in the mountains dont help stabilize the pack, there is not going to be as rapid aging and transformation of the crystals as with warm weather. In order to stave off the hazard, we need some prolonged warming, and rain, with as little new load on the pack as possible, or, if there is new load, then a hell of alot of it to compress and stabilize that first layer. I think you'll see lots of slide activity in the alpine either way the next time it snows!! Alex  Addendum: areas where hazard will be worst, will vary. * On N facing slopes that are not exposed to sun, you'll have little consolidation, to this will be more hazardous, but thats pretty typical in almost any snowpack. * I think this snow will be more susceptible to wind transfer than usual, so leeward slopes will get heavily loaded, and slab packs could form more so than they typically do in the Cascades, where the snowpack settles very quickly due to water content, weight and temps. I think anywhere where the snowpack can be loaded by wind transfer are places to avoid during the next cycle. * Below treeline, this is reversed. Wind transfer, hoar formation less likely to occur, so I'd say the alpine zone is going to be more prone than usual to large releases, depending on the next cycle. But consider: with a cold, weak ground layer, if we get significant precip in the alpine during the next cycle, you could see very large slab releases that go down to the ground! Ugly! Run for cover! [This message has been edited by Alex (edited 11-14-2000).] Quote Link to comment Share on other sites More sharing options...
jon Posted November 15, 2000 Share Posted November 15, 2000 One thing I have been pondering for the past month is what type of snowfall we will have this year. This past summer and fall has been exceptionally dry considering how wet it has been the past two years, certainly not the three months of continuous rain we saw. What I’m wondering is whether this will transpire into a dryer winter, where the snow is lighter than usual, and possibly a lower base than usual. I haven’t had the opportunity to ski/climb anywhere east of the cascades and thus been accustomed to the cascade crud. I’m wondering what it is like to carve some turns in really dry stuff. In addition to Alex’s thoughts, I’m wondering how non north facing faces (say that five times really fast) will pack. Since the sun is shining on them, whether it is freezing or not during the day, wouldn’t that cause them to ice up and make them more susceptible to slides? If this is the case, I presume that it would take some real wet weather early on here to change this or else we are in for a pretty dangerous season. Am I correct in thinking this? I took a class a few years back but we never got as far as how the pack changes over time. Maybe they could film the sequel to Vertical Limit here this winter! [This message has been edited by jon (edited 11-15-2000).] Quote Link to comment Share on other sites More sharing options...
Lowell_Skoog Posted November 15, 2000 Author Share Posted November 15, 2000 I think Alex's analysis is good. I posted the question after skiing near Mt Baker ski area last weekend. There was nice powder on permanent snowfields, but it was poorly bonded on steep slopes. It was plain that the cold temperatures were turning the new snow to sugar (faceted snow, depth/surface hoar, temperature gradient snow, whatever). Based on these observations, my theory is that new snow over perrenial snowfields could become very unstable with the next storm. North faces will be the worst because the current layer will be weakest there. Around Mt Baker at least, the snowpack is still shallow enough that there are a lot of terrain anchors exposed, so areas that don't have perrenial snow may not be so bad. (Don't go betting your life on it right away though.) Warm weather and rain would be the best way to get rid of this problem, but that doesn't look likely. It will be interesting to see what the Avalanche Center has to say about it when they start forecasting later this month. I consider it a good learning tool to compare my own observations with what the NWAC and their informants say. By the way Alex, when you mentioned the "temperate snowpack" of the Rockies, did you mean "temperature gradient snowpack" or maybe "continental snowpack"? "Temperate snowpack" sounds like normal Cascade conditions, although I think "maritime snowpack" is the usual term. (Just a terminology question--your analysis seemed excellent to me.) Lowell Skoog lowell.skoog@alpenglow.org [This message has been edited by Lowell Skoog (edited 11-15-2000).] Quote Link to comment Share on other sites More sharing options...
Alex Posted November 15, 2000 Share Posted November 15, 2000 "Continental snowpack" is the term I should have used, thanks! Quote Link to comment Share on other sites More sharing options...
gapertimmy Posted November 20, 2000 Share Posted November 20, 2000 I was up at snow lake on Thursday of last week and the snow on the northern side of the ridge was really interesting. The top layer had these huge, almost inch-long crystals, and underneath was rocky mountain-esque powder here is a pic of the crystals on the top layer of the snow: doesn't look like a very stable layer. As someone else said though, since this original snow fall was so small, there is still quite a bit of land-feature anchors for the next fall to cling to. Quote Link to comment Share on other sites More sharing options...
Lowell_Skoog Posted November 20, 2000 Author Share Posted November 20, 2000 A couple friends and I skied (to use the term generously) the Interglacier on Mt Rainier on Saturday. Actually, we ended our tour at St Elmo pass because we were running out of time. Based on this tour, I think the hazard on high old snowfields is not so bad. The weather last week was pretty warm and there was a fair amount of wind. The Interglacier had more windcrust than faceted snow. I think the faceted snow is only prominent in cold wind sheltered spots. Most of those spots are in places where terrain and vegetation anchors are still exposed. So, maybe we aren't developing a hair-trigger base. We'll see... Lowell Skoog lowell.skoog@alpenglow.org Quote Link to comment Share on other sites More sharing options...
Alex Posted November 28, 2000 Share Posted November 28, 2000 looks like the local forecast is starting... http://www.seawfo.noaa.gov/products/SABSEA "A 2 week period of dry cool weather prior to last weekend caused considerable faceting and weakening of previous snow. In addition significant accumulations of very weak surface hoar up to .5 to 1.5 inches had developed on most shaded and wind sheltered slopes. In many areas the overall shallow snow cover, terrain and vegetation anchoring should still be limiting the avalanche potential on many slopes. But the underlying layers may only marginally support potential new slab layers and new snow. This should be most likely a bit east of the crest and near the Cascade passes where less warming and rain may have been seen during the weekend storm cycle. Generally avalanches should be most likely on perennial snow and on slopes with a smooth underlying ground surface." Quote Link to comment Share on other sites More sharing options...
Guest Posted December 2, 2000 Share Posted December 2, 2000 Good beta guys. And cool photo, Tim Mountain Dude. Quote Link to comment Share on other sites More sharing options...
mikeadam Posted December 6, 2000 Share Posted December 6, 2000 ## [This message has been edited by mikeadam (edited 05-14-2001).] Quote Link to comment Share on other sites More sharing options...
mikeadam Posted January 2, 2001 Share Posted January 2, 2001 ## [This message has been edited by mikeadam (edited 05-14-2001).] Quote Link to comment Share on other sites More sharing options...
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