Avalanche Forecast

Issued: Jan 30th, 2021 4:00PM

The alpine rating is moderate, the treeline rating is moderate, and the below treeline rating is low. Known problems include Wind Slabs.

Avalanche Canada cmortenson, Avalanche Canada

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Asses how much new snow is underfoot as recent snow sits on top of a couple surface hoar layers. Be prepared to dial back your terrain selection if you see signs of instability, if over 20 cm of fresh snow builds over the day or if wind starts blowing snow into wind slabs.  

Summary

Confidence

Moderate - Uncertainty is due to the timing, track, & intensity of the incoming weather system.

Weather Forecast

An offshore low will push bands of warm air and precipitation in upcoming days which make it challenging to forecast the precise timing, temperatures and total snowfall amounts. 

Saturday night: Cloudy with clear periods and isolated flurries, trace to 5cm of new snow, moderate to strong south wind and alpine low temperatures -11C. 

Sunday: Cloudy with snow flurries, 5-10 cm new snow, strong south or southeast winds, alpine high temperatures around -5C with freezing levels rising to 120 0m.  

Monday: Cloudy with isolated flurries and clear periods, 5 to 15 cm new snow, moderate south wind and alpine high temperatures around -9C.

Tuesday: Cloudy with sunny periods and isolated flurries, trace to 3 cm new snow, moderate southwest wind gusting strong and alpine high temperatures around -10C.

Avalanche Summary

There have been no recent avalanche reports in the region, although we anticipate increasing moderate to strong south winds may form wind slabs to form in open alpine, exposed ridge crests and open areas below treeline. This MIN from Friday reports that recent 10-15 cm is sluffing easily and is great evidence of how slippery the surface hoar layer/crust/facet layer is and how reactive it might be once more slab properties exist in the snowpack.  

We're continuing to track a layer of surface hoar from early January (buried 50-80 cm) which has been trending towards unreactive, but was previously a concern in the North Blue River valley. The most recent activity reported on this layer comes from January 16, when professional operators reported a small (size 1) avalanche releasing 40 cm deep. This and snowpack tests that continue to sporadically produce easier, more sudden snowpack results make this layer worthy of continued monitoring.

Snowpack Summary

Another trace to 10 cm is forecast to fall overnight Saturday and throughout the day on Sunday. This will bring recent snow totals from ZERO to 25 cm, and expect surface conditions to be equally variable. This trace-25 cm of recent snow has buried a weak layer of surface hoar that reported to be widespread and sits on a variety of old surfaces including old wind slabs, soft faceted snow or thin crusts in steep solar. Below 1600 m, 30-40 cm of snow is settling above a decomposing melt freeze crust. Check out this MIN from Chappell creek. 

A weak of layer of surface hoar and crust from early January can now be found buried 40-90 cm deep. The curst tapers above 1700m. This layer last demonstrated reactivity over a week ago (Jan 16) in the south of the region near Valemount. It is most suspect in sheltered, open slopes at and below treeline. Although results from recent snowpack tests show increasingly resistant results (check out this MIN from near Barkerville), slope-specific assessment is warranted. 

Deeper in the snowpack, a couple of older persistent weak layers may still be identifiable from late and early December, consisting of surface hoar and a crust with faceted snow and buried anywhere from 70-150 cm deep. Prolonged periods of inactivity and unreactive snowpack test results suggest that these layers have trended towards dormancy. 

Terrain and Travel

  • Wind slabs are most reactive during their formation.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.

Problems

Wind Slabs

An icon showing Wind Slabs

If forecast snowfall (an additional 5-15 cm by Sunday afternoon) and wind values (moderate to strong south) are experienced, anticipate touchy wind slab formation. This new snow adds to the trace to 15 cm reported on Saturday. Wind slabs will be particularly touchy anywhere they sit on top of a slippery surface hoar layer. Reactive wind slabs will likely form in open alpine terrain, leeward pockets at ridgecrests, around exposed terrain features and in open areas below treeline.

Aspects: North, North East, East, West, North West.

Elevations: All elevations.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Jan 31st, 2021 4:00PM

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