Above 2,500ft Moderate
1,500 to 2,500ft Moderate
Below 1,500ft Low
Degrees of Avalanche Danger ?
More of the same this weekend. Our beleaguered snowpack hasn’t changed much in the last few weeks of cold, dry weather. We’ve had a few wind events from the north and the south, and a few inches of snow to soften things up in protected areas. We’re still hearing reports of good skiing to be found in places the winds haven’t hit, so keep searching, they are out there! (Hint: think north aspects around treeline, and protected glacier areas) Everywhere in between will be a dust-on-crust situation or just hard packed wind board/crust. The main danger to look out for will be recent/fresh wind slab on cross-loaded and wind loaded slopes/gullies steeper than 30 degrees.
Problem #1: Wind Slab
Location: Wind loaded slopes (possible on all aspects) and cross-loaded terrain features/gullies, above 1,500ft. Monday brought strong south winds, and north winds since then will reverse the wind loading pattern over exposed ridges and mountains. Any 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 and 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 (< 1.0m deep). Likelihood of triggering: low but still possible. Confidence: low. 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 thin areas, and carefully evaluate the presence of this potential danger on steep slopes, and especially on unsupported slopes.
Recent Avalanche Activity
In the last two weeks there has been small natural wind slab activity on wind loaded slopes, with crowns up to 25-50cm thick. This is occurring regularly in sync with wind events. Cross-loaded slopes have shown the most activity since the winds have shifted direction several times.
High pressure will once-again make for a beautiful weekend. Expect clear skies, moderate-strong north winds near Haines, and moderate winds in the Transitional and Pass zones. Alpine temperatures will mostly be in the teens F. The next possibility for a storm will be around Tuesday.
|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
|40″||0″ / 0.00||3″ / 0.30||0||light, N||0″/ 0.00 *|
Flower Mountain @ treeline
|33″||0″ / 0.00||1″ / 0.10||0||light, NW||0″/ 0.00 *|
Chilkat Pass @ 3,500ft
|20″*||0″ / 0.00 *||1″ / 0.10 *||0||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