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Archived

Avalanche Forecast

Dec 17th, 2017–Dec 18th, 2017
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
1: Low
The avalanche danger rating at treeline will be low
Below Treeline
1: Low
The avalanche danger rating below treeline will be low
Alpine
3: Considerable
The avalanche danger rating in the alpine will be considerable
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate
Alpine
2: Moderate
The avalanche danger rating in the alpine will be moderate
Treeline
2: Moderate
The avalanche danger rating at treeline will be moderate
Below Treeline
2: Moderate
The avalanche danger rating below treeline will be moderate

Regions: Lizard-Flathead.

While unlikely, if storm totals exceed 15cm on Monday then the danger rating will be moderate at all elevation bands as fresh storm slabs begin to form.

Confidence

Low - Timing, track, or intensity of incoming weather system is uncertain on Tuesday

Weather Forecast

Zonal flow should be firmly established by Monday morning. Two pulses established within this flow are expected to deliver modest quantities of snow and wind to the Lizard and Flathead ranges through Tuesday evening. The models currently show 5 to 10cm for each 12 hour period between Monday morning and Tuesday night, but there is potential to double these amounts on Tuesday. Stay tuned for more details. MONDAY: Overcast, freezing level starting at 600m rising to 1000m in the afternoon, moderate to strong southwest wind, 2 to 10cm of snow possible. TUESDAY: Overcast, freezing level near valley bottom, light variable wind at valley bottom, potentially strong southwest wind at ridge top, 5 to 20cm of snow possible. WEDNESDAY: Overcast with some clearing in the afternoon, freezing level at valley bottom, light variable wind, 1 to 5cm of snow possible.

Avalanche Summary

No new avalanches observed on Sunday. On Friday and Saturday small sluffs and soft slab avalanches were reported to size 1.Please submit your observations to the Mountain Information Network.

Snowpack Summary

The region was hit hard by wind over the weekend, but there may be protected areas where up to 10cm of new low density snow survived. At or just below the surface there is a wide range of conditions. Windward slopes have been scoured down to the old rain crust and/or rock. Sun and temperatures crusts have formed on south through west facing slopes. In sheltered terrain at and below treeline, large feathery surface hoar and sugary facets exist. Roughly 30 to 60cm below the surface you should be able to find a hard crust that was buried near the end of November. This crust is approximately 30cm thick and extends from 1600m to mountain top on all aspects. Below this crust, the snowpack is moist to ground. Average snowpack depths at treeline in the region range from 70 to 110cm.

Avalanche Problems

Wind Slabs

Continued strong winds Monday are expected to form fresh sensitive wind slabs that will be most prevalent immediately below ridge crest and behind mid slope terrain features. While small, these slabs may be problematic in complex terrain.
Use ridges or ribs to avoid pockets of wind loaded snow.Be cautious as you transition into wind affected terrain.Be careful with wind loaded pockets, especially near ridge crests and roll-overs.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood: Possible - Likely

Expected Size: 1 - 2