Above 2,500ft Considerable
1,500 to 2,500ft Moderate
Below 1,500ft Low
Degrees of Avalanche Danger ?
Problem #1: Wind Slab
Location: Wind loaded slopes (NW-N-NE aspects) and cross-loaded terrain features/gullies (E and W aspects), above 1,500ft. Yesterday’s new snowfall was blown around by strong S/SE winds above 1500ft. Alpine slopes in the lee to this wind pattern will be loaded up with fresh snow, and these fresh wind slabs will be sensitive to human triggers on slopes 30 degrees and steeper. Wind slabs will be 15-45cm thick, with the sliding surface being the new/old snow interface where we have a thin layer of faceted snow above a slick ice crust/wind board.
Stick to areas where the top layer of snow is protected from the winds and not forming a cohesive slab. Always practice good travel techniques, utilizing safe zones, escape routes, only exposing one person at a time to slopes over 30 degrees.
Problem #2: Persistent Slab
Location: all aspects above 2000ft where the snowpack is thin (< 1.5m deep). Below the upper rain crust, recent cold weather has been slowly faceting (weakening) the layers in the midpack and at the ground in thin, windswept areas. We have been getting reports of significant weakness within these faceted layers where the snow is thinner, and it’s safe to assume these conditions are relatively widespread wherever the snowpack is thin. Be aware that in these areas, you may be able to trigger pockets of deeper slab. Use extra caution in these areas.
Recent Avalanche Activity
In the last two weeks there has been increasing small natural wind slab activity on wind loaded slopes, with crowns up to 25-50cm thick.
Snow totals from Monday are less than expected, coming in at about 2-4″ at treeline. South winds were strong during the storm. Skies will be clearing today and remain that way through Wednesday. Some snow is possible Thursday-Friday but the track of the storm is uncertain at this time.
|Snow Depth [in]||Last 24-hr Snow/SWE [in]||Last 3-days Snow/SWE [in]||Today’s Freezing Level [ft]||Today’s Winds||Next 24-hr Snow/SWE|
Mount Ripinsky @ treeline
|38″||2″ / 0.20||2″ / 0.20||200||light, N||0″/ 0.00 *|
Flower Mountain @ treeline
|33″||1″ / 0.10||1″ / 0.10||200||light, NW||0″/ 0.00 *|
Chilkat Pass @ 3,500ft
|21″*||1″ / 0.10 *||1″ / 0.10 *||200||light, NW||0″/ 0.00 *|
( *star means meteorological estimate )
Additional Info & Media
If you get out on the snow, send in your observations!
We will be providing an AIARE Avalanche Level 1 Class this winter in Haines, February 23-25, 2018