Above 2,500ft Moderate
1,500 to 2,500ft Considerable
Below 1,500ft Low
Degrees of Avalanche Danger ?
Problem #1: Wet Avalanches
Location: Sunny aspects, mainly below 3,000ft. We’re now in freeze-thaw conditions at mid- and lower elevations, with low avalanche danger early morning while the snow is frozen hard, but becoming more dangerous as solar radiation softens the snow. Wind slabs from new snow over the last two weeks have built up on E-S-W aspects, sitting over an impenetrable ice crust. These slabs are well bonded, but strong solar radiation and warm temperatures will cause melting/softening during the daytime, weakening the bonds between layers and the strength of the slabs. Human triggered wet slabs and large wet sluffs will be likely in the afternoon on sunny slopes steeper than 30 degrees. If the snow softens to ankle-deep or more, it’s time to get off steep slopes. Always utilize safe terrain and group management techniques, and avoid traveling solar aspects during the heat of the day.
Problem #2: Wind Slab
Location: Wind loaded E-S-W aspects, treeline and higher. 2-3″ of new snow that fell this week has been whipped around by Northerly winds over the last few days. In isolated wind loaded areas, this new snow has formed fresh wind slabs up to 8″ thick. These slabs are tender and poorly bonded. Keep an eye out for wind loaded slopes where these fresh surface slabs may be thick enough to sweep a person down into high-consequence terrain.
Problem #3: Deep Slab
Location: All aspects above 1,500ft. Especially at the Chilkat Pass. Confidence: Low Now that the midpack is solidly re-frozen, a strong bridge exists over the main weak layer (old facets 1m deep in the Lutak zone and 30-45cm deep in the Pass). In most areas, it will be nearly impossible to penetrate the upper frozen ice layer. BUT, in areas where the snowpack is thin, it may still be possible to trigger basal facets or depth hoar which could propagate into areas of deep slab. The likelihood of this happening is generally low, but still possible. Use extra caution to avoid thin rocky areas at the margins of a slab. Be careful when approaching summits, ridges, and other windswept areas. Unsupported slopes will be most likely to slide in this scenario.
Recent Avalanche Activity
During the freeze-thaw conditions over the weekend (March 17th-18th), reports from the field included one human-triggered wet slide at the Pass, and isolated whumphing/collapsing still happening in all zones.
There was a widespread avalanche cycle (March 10th-13th), mostly size D2-D3, a few D4, all aspects. Failure planes appear to have been both above and below the Jan. ice crust, within storm snow, and on depth hoar at the ground in some rocky areas.
Snow totals from this week are around 2-3″. Thursday-Sunday will bring periods of sun and periods of clouds, with light-moderate north winds. Strong solar radiation is likely in the afternoon each day. After a solid freeze each night, freezing levels will rise to near 2,500ft during the afternoon.
|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
|61″||0″ / 0.00||3″ / 0.25||0 -> 2500ft||light, N||0″/ 0.00 *|
Flower Mountain @ treeline
|45″||0″ / 0.00||2″ / 0.15||0 -> 2500ft||light, NW||0″/ 0.00*|
Chilkat Pass @ 3,500ft
|26″*||0″ / 0.00 *||2″ / 0.15 *||0 -> 2500ft||light, NW||0″/ 0.00 *|
( *star means meteorological estimate )
Additional Info & Media
If you get out on the snow, send in your observations!