Confidence: High. Distribution: Isolated to Specific. Protected terrain features on leeward slopes is most likely where surface hoar has survived the winds and is buried. Strong northerly outflow raked higher elevations this past week and deposited wind slabs on E-SE-S-SW-W aspects. Specific terrain features lower down on slopes and below treeline on all aspects, are areas that wind slab, or recent deposits may have built over persistent weak layers. These sheltered, or protected areas may be tempting for riders looking for soft surface conditions, but where triggering a persistent slab is the most possible. New snow has covered up some visual clues of wind deposited snow and loading patterns. Avoid slopes greater than 30 degrees, be especially careful of safe zones, dig and look for layers to make specific hazard assessments.
New Persistent Layers and Snowfall Timeline
Old Persistent Layers
(Surface hoar near-treeline in the Transitional Zone 1/31. Once buried by wind slab or new snow these feathery crystals become a dangerous persistent weak layer that will require extremely careful assessment and overall immediate avoidance in avalanche terrain. Photo: Jeff Moskowitz)
Examples of top loading and cross loading (click image to read more).
D2 Slab in cross-loaded terrain. Transitional Zone, NE aspect, 1500ft. Photo: Erik Stevens. 2/4/2021
There has been little observed activity in the last week, but this D2 pocket slab from the last few days is a good example of wind slabs lurking in cross-loaded pockets. These slabs are sitting on very weak surface hoar or facet layers and will be ripe for human triggering.
Bottom Line: The snowpack is more complex than it was a week ago, with strong northerly outflow, intermittent snowfall, bouts of surface hoar and cold temperatures that promoted faceting. Searching out soft snow conditions may be tempting, but remember that protected or sheltered area may harbor dangerous persistent weak layers, including surface hoar that are possible for human triggering. A stepping back, status quo, or assessment mindset are essential to mitigate the current hazard. Avoid steep gullies, ravines and terrain traps at convexity and roll-overs, or anywhere snow could pile up quickly. Hard wind slabs may be difficult to trigger, but large, destructive, and unpredictable. If triggered, they are most likely to release above you.
Frigid temperature this past week included a crescendo of northerly winds from Jan. 30 – Feb. 2 when the Haines Pass weather station reported sustained wind speeds of 35mph and low temperatures of -10F. A dusting of very low density snow was reported in Haines Feb. 3 at 57:1 snow to water ratio. An ice fog in the Lutak Zone was reported Feb. 4 with temperatures at elevation rebounding to the mid-teens to twenties during the day. Expect a mix of clouds and sunshine while temperature drop into the single digits overnight and increase during the day, as more northerly outflow winds continues through the weekend.
( *star means meteorological estimate )
—The Mt. Ripinsky weather station is completely buried and no longer reporting snow depth.—
Practice like you play. Make sure all your rescue gear it is fully functional and your beacon has full batteries. Make sure 1) everyone in the group has a functioning beacon, shovel and probe 2) knows how to use them and 3) has trained in companion rescue in the last year. Keep your skills fresh. If you head into the hills, watch out for red flag avalanche conditions, natural avalanches, whoomphing or collapsing, and shooting cracks.
Education Video Links:
Click the + Full Forecast link below for each zone to read more. Submit observations. Win prizes. Each observation will be entered in a raffle drawing, this month’s prize a 1-hour massage gift certificate from Haines Body Work and Restorative Massage. Submit confidential reports and findings to [email protected]
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