YAA CAC Techs - White Pass West Conditions Report

March 30th, 2012

Today we headed up into the Byrant Pass area.

We’ve had just under 10 centimeters of new snow in the last couple of days with moderate winds from the south forming isolated pockets of wind slab up to 20 cm deep in isolated spots. We triggered one size 1 slab avalanche  on a steep cross loaded feature just bellow ridge line

The morning was warm and sunny with convective clouds starting to build in the afternoon.  The sun was strong when it broke through the clouds and was baking south facing slopes where we found wet snow about 20cm deep.  I think the scattered clouds saved us from a widespread wet avalanche cycle today.

 Another problem we were wary of with the warm spring temps is cornice failure, we travelled cautiously whenever we crossed slopes with cornice hazard overhead.

Associated with cornice failure is our old friend, the surface hoar layer that was buried in mid February.  We are still finding it in isolated areas on North aspects and although we haven’t seen any recent avalanche activity on this layer lately I suspect that may be due to the fact that it is hasn’t seen a significant load recently.  We've seen cornice failure trigger this layer in the past and it was on my mind again today.

That said Justin and I found some great skiing today especially on east facing slopes that hadn't seen much wind.

 

March 31, 2012 WOW we had a great day in the mountain today. We spend the day over on the East side of the pass. South facing slopes which were getting wet by the end of the day yesterday had frozen again overnight making for an "chattery" first run down from the sleds. The east side of the pass over all does not seem to have seem to have seen as much week over the last week and we found only isolated pockets of wind slab. In steep terrain the snow was sluffing easily and building mass on the slope meaning some sluff management was necessary :). Air temperatures in the Alpine remained cool through out the day although the strong sun did heat up the snow on those steep south facning slopes again. To get back to our snowmobiles at the end of the day we had to climb one of these slopes but we managed the hazard by waiting untill the sun had moved off to the west and the snow had time to cool off and start setting up. Even then our "spider sences" were tingleing and we decided after we got to the top the we could probably have affored to wait even a little longer. Hope everybody else enjoyed themselves out there as much as we did! Cheers, Eirik and Justin

April 3, 2012

Another beautiful day in the mountains.  We started out by digging our weekly full profile at Fraser Wx plot.  Well settled recent storm snow sits on top of a strong and supportive mid and lower snowpack.  Compression tests produced no results in the upper snowpack.  Compression tests produced no results.

We then headed via snowmobiles to Byrant Lake Pass.  Onroute we were observing the North and South facing slopes around Byrant Lake.  We were particularly interested in any cornice failures on the North Aspects occurred during the warm temperatures this past weekend.  No cornices were observed, however many looked large, drooping with not much support remaining.  On the South Aspects, we observed numerous wet loose snow avalanches to size 1.5, predominately originating from cliff bands and rocky outcrops.  These all seem to be running within the recent storm snow on an old sun crust.

Convective cells dominated the day and winds were light-moderate from the South, with light snow transport moving around the approx 5-10cms of storm snow that fell overnight.

We skied the NW facing slope that leads down to Crater Lake/Chilkoot pass.  The recent storm snow made for good turns.  The surface snow became moist around 1200m.  

Cheers,

Justin

Good day of skiing in the White Pass. As we move into spring we are noticing a couple of changes out there. Obviously we're moving into spring avalanche cycles where tempererature and solar radiaion are the driving factors behind most of the avalanche hazard. Spring weather patterns also have a specific effect. Whilst over the winter we saw most of our snow and wind associated with the passage of frontal weather systems we are starting to see convective activity have a more pronounced effect. Convective weather can bring highly variable amounts of snow and wind. This week for example saw 3 cm fall in our weather plot at Fraser with little wind. Where we were skiing on the east side of the pass though there was over 20cm of recent storm snow which had been heavily wind effected in places. Our main concern today was wind slab. Temperatures remained mild overnigh and the forecast was for scattered cloud cover so we anticipated wet slides on the south aspects and avoided spending time under any large south facing slopes. In the end the temperatures remained cool and the skies stayed cloudy so we didn't see any sun triggered avalche activity today. Finally, even though we havn't seen any recent avlanches on this layer the feburary surface hoar layer remains a concern on shelted north aspects. I hope you all Have a great weekend in the mountains.

April 10, 2012 Along the highway corridor we observed a few natural loose wet snow avalanches on east aspects in the transitional snowpack region. These avalanches ran half of their runout zone. High overcast clouds moved in during the afternoon. Plus 2 degrees was observed at 1200m on a north aspect with calm winds all day. Inversion was observed via remote weather observations, but field observations proved it to be a good overnight recovery. Snowpack- Well settled powder snow supported by a strong mid and lower snowpack allowing for good travel conditions, with alright skiing on Log Cabin Mountain. We skied 30-35 degree north facing terrain in the alpine. Hope everyone had a great easter weekend!

April 11, 2012-Observations today were taken from Powder Valley (transitional snowpack region). Weather: Mostly overcast skies, +12C was recorded at 800m and +2C at 1650m, winds light from the NE. Snowpack: Moist surface snow observed on all aspects to ridge-top. At 1100m on South Aspect, Moist snow was observed to ground, HS was approx. 130cms. A Profile on a North Aspect (1650m) revealed 20cms of moist snow sits on top of a 1F-P+ slab overtop of two SH layers down 55 and 65cms. The lower layer (feb 21) was still producing Hard “pop” results. Avalanche Observations: One Na loose wet size 1.5 on an East aspect at 1500m elevation, suspect it released some time mid day. Our Travel concerns today were loose wet and wet slabs on solar aspects as well as East and west aspects. Over the past weekend, we have seen a majority of wet avalanche activity on East aspects, indicating the morning sun is really starting to penetrate the upper snowpack and play an affect. We are continuing to watch the Feb 21 SH layer down 65cms, still producing results to stability tests.

Justin and I travelled by snow machine in the area east of White Pass today. Few clouds and warm (3.5C) in the outhouse parking lot at 1130hrs. Moderate NE winds in morning turned calm by midday. Overnight temperatures have been staying warm and snow conditions were moist but still supportive enough to allow for easy travel on sleds. Numerous loose wet avalanches up to size 2 were observed on south aspects. Warm temperatures are also producing small wet loose avalanches on north aspects. One of our objectives today was to investigate the SH hoar layers still present in the snowpack. We found this layer at 1600m on a north aspect and it was still moderately reactive down 50cm however, not reactive to ECT. Another layer to keep in mind is the December 5th crust still present in most places up to 1500m. With solar aspects going isothermic to depths nearing this crust layer, there is a possibility that it could wake up and produce larger avalanches. Cornice activity was another target today. No cornice failures were observed, however, with warm temperatures persisting, it is likely only a matter of time.

Just wanted to share a picture of the numerous wet loose avalanches we saw today.  We also observed a glide crack release on the East aspect of Summit knoll.  This is where free water percolates through the snowpack and pools at a basal layer and smooth interface (in this case it is smooth granite rock).  This same phenomena can occur with persistent weak layers as well (such as an early season crust that James talks about above).  This is usually the culprit for large destructive spring time avalanches.  

Of note the Dec 5th crust was down 100cms on a morainal feature at 1500m in the alpine.  We observed isothermal temperatures to that layer on a south aspect.

 

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Justin and I are in Fraser this week so we were able to get an early start in White Pass this morning.  Weak recovery overnight with temperatures only going down to 0.3 degrees at both Summit and Fraser wx stations.  Skies were broken in the morning with very light winds from the SE. 

Traveled by snow machine up Waterfall drainage just east and across the lake from Fraser Highways camp.  The slight refreeze overnight made conditions challenging but doable on the sleds in breakable crust.  The weather started to move in once we got in the alpine with a weak low producing a short storm that killed visibility.  The small system was accompanied by moderate SE winds and graupel in the alpine.  Precipitation came in the form of light rain at tree line elevations during the storm.  We were driven out of the field early by fears that the lake would be uncrossable with afternoon warming.  Our suspicions were confirmed when we met with moist snow and overflow on the lake surface on the return crossing.   Through the afternoon the skies again cleared and temperatures stayed warm.

No new avalanches observed today but would suggest paying attention to normal spring patterns with daytime warming likely to produce loose wet slides and cornice failures. 

Skiing conditions very marginal in the White Pass area with variable crust in the alpine and isothermic conditions at tree line elevations.

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Clear skies and cold temperatures overnight here in White Pass allowed for a good refreeze in the upper snowpack.  Stability was good so we headed up to north Taiya via Bryant Pass.  Objective for today was to continue to monitor spring conditions at treeline and in the alpine. 

Travel on skis was a little challenging this morning on the bomber crust that had formed overnight.  Ski crampons are definitely worth carrying this time of year for those cold, early morning starts.  Snow conditions were relatively good with 5cm of new snow on top of the crust.  Despite the intense sunshine, temperatures in the high alpine stayed relatively cool only reaching about 3C at midday.  Relatively dry snow conditions on the surface persisted through the afternoon with only a slight bit of moisture in the surface snow on solar aspects. 

On the way up through Bryant Pass on the far side on the lake we did observe a few slab avalanches to size 2 on sheltered, shaded, north features.  Though these slides are likely a week old, they are worth mentioning because though we had continued to suspect further slab activity this spring we had not observed much in recent weeks.  Seeing these few avalanches confirmed our suspicions and were a good reminder that there are still persistent weaknesses in the snowpack that we need to be mindful of.  This particular avalanche was triggered on a relatively steep north feature in a shallow area.  The slab slid on facets that likely formed in mid-late February.

So it was a pretty classic spring outing today.  We confirmed a good overnight refreeze and we got an early start.  We planned a descent of a north feature and avoided south aspects during the heat of the day.  We gave cornices a wide birth and found some decent skiing on a steep north slope and more mellow south features.    

Please see photos below in the next post and check the Yukon Avalanche Youtube Channel for a short video on what we saw today.

It’s been great helping out with the program these last couple of weeks.  Big thanks to Justin and Eirik for making me feel like part of the team.  James.

Natural Slab avalanche failing on a layer of facets.  Note the steep rocky terrain, a shallow, weak snow pack area.  Think about skiing where the snowpack is deeper, avoiding these type of rocky outcrop slopes.  We suspect these avalanches released in the height of the warming trend, approx 1 week ago.  The trigger was likely a point release avalanche and/or the warming trend rapidly settling the upper snowpack.

5-10cms of new snow on top of the melt-freeze crust made for good skiing.

Thanks for a great season!

the video referred to in the second last sentence doesn't seem to be up on youtube

Thanks Jim, the video should be up now: Click here to view the video.