The parade of storms continues across the forecast region. Beginning yesterday afternoon, the 4th system since February 1st moved in. Overnight, between 5-10″ of snow has fallen with ridgetop winds in the 30-40mph range and gusts in the 70’s. We can expect another 3-5″ through today with decreasing easterly winds (15-25mph). Temperatures have risen enough for rain to fall at sea level and the rain/snow line sits around 300′. After a brief lull this afternoon, the 5th weather system for February will ramp up tonight and extend through midday tomorrow.
With anywhere from 8-14″ of new snow by midday today, along with the strong winds, we can expect to see all the classic storm snow avalanche issues. These are storm slabs, wind slabs, sluffs, and cornice falls. Even though the storm will be tapering today, we still need to be on our guard.
Storm slabs: In areas seeing over 8″ or so of new snow, watch for storm slabs. Warming temperatures during the storm likely caused denser snow to fall over lighter snow (an upside-down storm). In this case, storm slab avalanches will be fairly shallow, essentially the depth of the new snow. Additionally, small surface hoar was seen yesterday before the snowfall in the mid elevations. This can add to the tenderness of storm slabs.
Wind slabs: We can pretty much bet on new sensitive wind slabs on wind loaded slopes predominantly in the Alpine. Slabs could be anywhere from 1-3′ thick depending on the amount of new snow/wind and easy to trigger. They may be lower on slopes than expected and in cross-loaded gullies due to the way the winds channel through terrain.
Loose snow avalanches (sluffs): Dry sluffs in the new snow in the mid and high elevations are likely and wet sluffs in the lower elevations.
Cornices: Once again, ridgelines are being impacted by strong winds and cornices continue to grow and break off. They are often the culprit for triggering fresh wind slabs below during periods of strong wind.
Graph of the winds during the past week at the Sunburst weather station (3,812 elevation). All wind events are from the east and except for Saturday, coincide with several inches of new snow. Note the pattern of the last three storms since last Tuesday and the stronger storm over us this morning.
To the south of Turnagian Pass and in Summit Lake, much less snow has fallen, but winds are likely affecting these areas as well. Here the snowpack is much shallower and weak layers surrounding crusts are buried in the top 2 feet of the pack. Keep in mind that new wind slabs that form could overload buried weak layers and create a larger avalanche.
Glide Avalanches: We are watching this crack pictured below in one of the most popular zones at Turnagain Pass. Keep you eyes peeled for these in the days to come and let us know if you see any additional cracks.
Glide crack that sits near the common motorized up-track. Chugach NF Avalanche Center Intern Allen Dahl took this photo yesterday. The crack is slowly opening and we should limit any time under it and watch it closely if in the area. 2.7.22.
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