Tatoosh 2/24
2/15/10
WA Cascades West Slopes South (Mt Rainier)
4230
13
I have been pretty lazy in writing TR's this season, as it seems I'm either working, skiing, planning to ski, packing, unpacking, or pondering the lameness of my occasional day trip to skin at Snoqualmie under closed lifts with the dog (where I always ski down in the confines of my uptrack ;)). But...
After considering what Brandonee and I experienced today, and the moderate avy report and forecast, I think a heads up is in order.
I would say today was one of the most active windslab days I've been out in, which is concerning, because there was also a lot of loading... on all aspects.
We departed Narada and skinned right up Narada face w/2-3" of new on old crust, nothing moving, as expected with that amount of snow and avy forecast, but as we headed south from Reflection it was obvious the snow was very slabby underfoot. It started snowing moderately and would continue all day increasing at times to what I would consider heavy. It snowed from above, and sideways; from the west, from the southwest, from the south and the southeast. Winds were not high, but there was a lot of snow being transported.
At around 5700' we isolated a switchbackout on a small NE facing roller to see what we already suspected might happen. Cracks stretched out 5-6' in front and behind, and they went deeper than telemetry would have indicated. A good 12" with snow still falling.
We took a protected route to the Castle/Foss saddle, in hopes that the south facing would be less loaded and more stable. It was less loaded for the most part, with some significantly crossloaded areas, but still slabby with a slippery bed surface.
We leapfrogged the safest terrain down to about 4300' w/o incident knowing that all new snow was suspect, and on the skin back up to the saddle, we noticed a SSW facing slope that had naturally released a 12-14" slab. Interesting because we had not seen any other natural releases on other steeper slopes with significantly more loading. I suspect we would have seen more, but vis was not so good.
We continued to ski the safest terrain with high suspicion, limited exposure, and acceptable risk (just how we like it). And yes, we did pass up a lot of REALLY tasty lines.
This is not a "you may die" warning, just a heads up for the conditions that seem to be local to the Tats and possibly the Paradise area.
Notable observations:
There were at least two layers in the transported snow. In the most common slab about 14" deep an easily propagated top 4" with the rest sliding on the crust. North facing crust bed was more slippery than south facing.
Significant loading on all aspects, except ridgetops where scoured, and in the trees.
Whoomphing, cracks, natural releases, and triggered releases all present.
A loud "crack" was heard by Brandon from Stevens Canyon Rd just after our departure. I didn't hear it, I was still gasping from trying to keep up with him all day!
Stay safe. Have fun!
After considering what Brandonee and I experienced today, and the moderate avy report and forecast, I think a heads up is in order.
I would say today was one of the most active windslab days I've been out in, which is concerning, because there was also a lot of loading... on all aspects.
We departed Narada and skinned right up Narada face w/2-3" of new on old crust, nothing moving, as expected with that amount of snow and avy forecast, but as we headed south from Reflection it was obvious the snow was very slabby underfoot. It started snowing moderately and would continue all day increasing at times to what I would consider heavy. It snowed from above, and sideways; from the west, from the southwest, from the south and the southeast. Winds were not high, but there was a lot of snow being transported.
At around 5700' we isolated a switchbackout on a small NE facing roller to see what we already suspected might happen. Cracks stretched out 5-6' in front and behind, and they went deeper than telemetry would have indicated. A good 12" with snow still falling.
We took a protected route to the Castle/Foss saddle, in hopes that the south facing would be less loaded and more stable. It was less loaded for the most part, with some significantly crossloaded areas, but still slabby with a slippery bed surface.
We leapfrogged the safest terrain down to about 4300' w/o incident knowing that all new snow was suspect, and on the skin back up to the saddle, we noticed a SSW facing slope that had naturally released a 12-14" slab. Interesting because we had not seen any other natural releases on other steeper slopes with significantly more loading. I suspect we would have seen more, but vis was not so good.
We continued to ski the safest terrain with high suspicion, limited exposure, and acceptable risk (just how we like it). And yes, we did pass up a lot of REALLY tasty lines.
This is not a "you may die" warning, just a heads up for the conditions that seem to be local to the Tats and possibly the Paradise area.
Notable observations:
There were at least two layers in the transported snow. In the most common slab about 14" deep an easily propagated top 4" with the rest sliding on the crust. North facing crust bed was more slippery than south facing.
Significant loading on all aspects, except ridgetops where scoured, and in the trees.
Whoomphing, cracks, natural releases, and triggered releases all present.
A loud "crack" was heard by Brandon from Stevens Canyon Rd just after our departure. I didn't hear it, I was still gasping from trying to keep up with him all day!
Stay safe. Have fun!
Thanks for the informative reporting Kneel...
Thank-you much for the report, I'll be heading up to P'dise today.
Conditions report much appreciated, and exactly the purpose for which Charles started this site. Thanks for taking the time to share your observations. Dance for snow, stay safe, grow old and ski more.
I'm not nearly as avi savy as i should be and consider myself more of a front country skiier (more on that later), but i was under the impression that the forecast was not as dicey as kneel found (or suspected). Am i wrong/missing something? Is this anomolous or well within the range of expectations given the forecast? I'm quite clear that great variation can exist and caveats are a given, but i don't generally see many reports that deviate much from expectations.
When you read the forecasts read the disclaimers also and look at the elevations of the forecasts. I also think the forecasts benefit from as many field reports as possible and i feel remiss at not posting that often (altho I usually report if I think conditions are sketchy). Another thing, this year I have noted much greater discrepancies between the wind velocities and snowfall amounts in backcountry Paradise and those reported by the NWAC telemetry station than I've noticed in the past decade or so. I haven't quantified my observations so it could be my imagination. But I would think the NWAC forecasters have to depend on field reports and telemetry--don't think they have a crystal ball (altho they seem to get a lot of reports from Crystal) ;D
The discrepancy is the reason I felt more compelled to post a conditions report. I've been getting the feeling that the reports from NWAC have become more general this season both in description and geographic area. Has anyone else noticed this? I'm not at all critical of this valuable resource for BC travellers. Quite the opposite, I think they need the BC community's support now more than ever, but I assume they are working with a shrinking budget, smaller staff, less contributions, and fewer Field trips.(?)
Anyways, I'm not an expert either, but the avy forecast is only one piece of info, and what's underfoot always supercedes the info garnered from the forecast for me. You may notice, however that the Paradise telemetry told part of the story: 9" new, and moderate winds. While the next closest Telemetry@ Crystal reported only 1" new. That kind of variance lets me know that a forecast for "WA Cascades west of the crest including Cascade passes" is not likely to be accurate for all areas/aspects.
I too like it when the forecast agrees with the conditions found, as we were disappointed with our discovery of yellow/red light stability amidst a blanket of fresh pow (although I was very happy that it was snowing!)
Have fun out there!
Anyways, I'm not an expert either, but the avy forecast is only one piece of info, and what's underfoot always supercedes the info garnered from the forecast for me. You may notice, however that the Paradise telemetry told part of the story: 9" new, and moderate winds. While the next closest Telemetry@ Crystal reported only 1" new. That kind of variance lets me know that a forecast for "WA Cascades west of the crest including Cascade passes" is not likely to be accurate for all areas/aspects.
I too like it when the forecast agrees with the conditions found, as we were disappointed with our discovery of yellow/red light stability amidst a blanket of fresh pow (although I was very happy that it was snowing!)
Have fun out there!
thanks guys. You both point out that it's good to hear about the anomalous info, which was why I asked. Like you said, kneel, 9" of new plus wind. Probably more than was expected. I'm happy to be reminded that avi forecasts, as good as they are, are very general in nature.
found lots of wind-affected snow and cross-loading today on a tour of Mazama Ridge; lots of snow wheels on south-facing slopes; powder in the morning and heavy, consolidating snow by early afternoon. 8-14 inches of new depending on where you tested.
Wish I had read this report before skiing the tatoosh on Thursday...
I set of two different slabs, both on north to northeast facing slopes.
The first one 100-150ft wide and a foot to a foot and a half deep.
The second one about 50ft wide with about the same depth as the first one.
They ran about 200ft moving very fast and stopped when the pitch mellowed out.
Should have skied a safer line.
Thanks for the report.
I set of two different slabs, both on north to northeast facing slopes.
The first one 100-150ft wide and a foot to a foot and a half deep.
The second one about 50ft wide with about the same depth as the first one.
They ran about 200ft moving very fast and stopped when the pitch mellowed out.
Should have skied a safer line.
Thanks for the report.
a guy set off a wet slide on the south facing (9-1-1) slopes of the back bowl of Mazama today, out ran it. All the snow we found was heavy and some pretty wet all the way out past the Cowlitz Divide.
Since I was the NWAC forecaster for the trip period (2-24-10) on the original Tatoosh post, I thought I'd chime in here before the topic becomes too speculative on forecast "discrepancies" or what the NWAC forecast did or did not say. And so that everyone can be more objective in their dissection of the forecast for Feb 24, I've included a copy of the detailed forecast narrative for the day and area under discussion. As indicated, the forecast was issued late morning of the 23rd and should have been available on the web site the day prior to the tour:
I would urge those of you who found unstable slab conditions to read the above and see if it adequately described the conditions encountered. Although the forecast for Wednesday morning was moderate it was increasing and trending toward considerable, with the graphic for the day showing considerable above 5 to 6000 feet for the afternoon period on the 24th.
In any case, no matter what the forecast, always be ready for unexpected conditions. While we do our best to provide the most reliable and detailed information available, some storms...particularly during this year of split flows...can be rather fickle and difficult for the models (and hence for us) to handle accurately. While the may lead to occasional "missed" forecasts, we do not miss the danger trends often.
Thanks for the informational posts.
Best--Mark Moore, NWAC
- Tuesday and Tuesday night: Moderate avalanche danger above 5 to 6000 feet and low below Tuesday morning slowly and slightly increasing later Tuesday afternoon and night.
Wednesday and Wednesday night: Further slowly increasing avalanche danger becoming considerable above 5 to 6000 feet and increasing moderate below.
Snowpack Analysis
The last few days of clear skies at slowly warming temperatures but continued light to moderate winds have produced a diurnal danger cycle...mainly in sun exposed but wind sheltered terrain...with surface snow slightly softening and weakening during the later morning and afternoon hours and refreezing and strengthening overnight. This has created a gradually more stable snowpack but highly variable snow surface. In most areas the upper part of the generally stable snowpack consists of either stable surface crusts with some melt runnels, wind hardened and scalloped surface snow layers, recycled powder or surface hoar. While decreasing amounts of loose surface snow have been available for wind transport, some isolated and mostly shallow wind slabs have developed and are lingering on northwest through southwest exposures above about 6000 feet.
Although the current avalanche danger is quite low, the surface snow layers that do exist...most notably the relatively widespread surface hoar that overlies crusts, recycled snow and wind slabs...are bad omens for future avalanche danger, especially if the hoar frost is buried intact.
Detailed Forecasts
Tuesday and Tuesday night
Increasing clouds are expected Tuesday morning with light rain or snow in the Olympics spreading into the Cascades during the afternoon and continuing Tuesday night. Along with lowering freezing levels and increasing winds, this should produce a gradual increase in the avalanche danger later Tuesday afternoon and night. While relatively light new snow accumulations are expected, mostly in the 1-4 inch range, some generally shallow but quite sensitive wind slabs are expected to develop over the very weak and extensive surface hoar that has been recently reported in many locations.
Wednesday and Wednesday night
A second and slightly stronger weather system should spread light to moderate rain or snow northward late Tuesday night and Wednesday morning, along with further moderate ridgetop winds at continued relatively low freezing levels. This should produce further slowly but significantly increasing avalanche danger as gradually thickening and increasingly sensitive wind slabs develop over previous crusts, recycled weak snow layers or surface hoar. Whumpfing and surface cracks should become increasingly likely on Wednesday, along with the possibility of remotely triggered avalanches. While most slides should be rather shallow and range from about 6-12 inches, some larger slabs of 1 to 2 feet or more may become possible on steeper north, northeast and east exposures at higher elevations. Although decreasing and more showery precipitation is expected Wednesday afternoon and night, light to moderate showers and moderate winds at relatively low freezing levels should maintain or slightly increase the avalanche danger as additional small loads are added to existing wind slabs.
As a result, careful snowpack evaluation, cautious routefinding and conservative decision making are strongly encouraged as some triggered avalanches may release on relatively low angle slopes, and sympathetic slabs are possible on nearby or adjacent terrain.
N/A
Backcountry travelers should be aware that elevation and geographic distinctions are approximate and that a transition zone between dangers exists. Remember there are avalanche safe areas in the mountains during all levels of avalanche danger. Contact local authorities in your area of interest for further information.
I would urge those of you who found unstable slab conditions to read the above and see if it adequately described the conditions encountered. Although the forecast for Wednesday morning was moderate it was increasing and trending toward considerable, with the graphic for the day showing considerable above 5 to 6000 feet for the afternoon period on the 24th.
In any case, no matter what the forecast, always be ready for unexpected conditions. While we do our best to provide the most reliable and detailed information available, some storms...particularly during this year of split flows...can be rather fickle and difficult for the models (and hence for us) to handle accurately. While the may lead to occasional "missed" forecasts, we do not miss the danger trends often.
Thanks for the informational posts.
Best--Mark Moore, NWAC
Mark, thanks for all the work you do. I, and everyone I ski with, read the NWAC forecasts almost daily. However, we do read the disclaimers and cautions and we are fully aware that macrostability and microstability are two different things and it is our responsibility as backcountry travelers not only to be aware but to be assertive in looking for signs of instability, probing the snow as we travel to look for layers, observing signs of wind activity, doing hasty pits, and, if we have any doubt, a full-blown pit.
Thanks again; your services are invaluable and that is why we lobby for your continued support and donate to the Friends of NWAC and to CSAC.
Thanks again; your services are invaluable and that is why we lobby for your continued support and donate to the Friends of NWAC and to CSAC.
While Rogets' may have them on the same page, I suspect that 'variation' is a more operable and useful term than 'anomolous' or 'deviation'. Thanks for the level comments, Mark.
Off to check the variation at Hogback.. :) dg
Off to check the variation at Hogback.. :) dg
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