Above 2,500ft Moderate
1,500 to 2,500ft Considerable
Below 1,500ft Low
Degrees of Avalanche Danger ?
As temperatures rise and the sun comes out today, wet slides will become possible on steep sunny slopes. We also have pockets of thin surface wind slab to watch out for. Keep your eyes open and be on the lookout for any surprises. Temperatures are starting around freezing at 2,500ft, and will rise to 40-45F today.
Problem #1: Wet Avalanches
Location: Steep E-S-W aspects below 3,500ft. As temperatures rise above freezing through the day and the sun shines in force, sunny aspects will be taking on a lot of heat. Melting and softening will increase the danger of human-triggered wet slabs and large, dangerous wet sluffs as the day goes on. Restrict travel on these aspects to the early-morning hours when the snow is still frozen. If the snow softens to ankle-deep or more, it’s time to get off those steep sunny slopes.
Problem #2: Wind Slab
Location: Wind loaded E-S-W aspects, treeline and higher. 2-3″ of new snow that fell last week has been whipped around by Northerly winds. In isolated wind loaded areas, this new snow has formed fresh wind slabs up to 8″ thick. 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. These wind loaded pockets may cause small areas of MODERATE danger.
Problem #3: Deep Slab
Location: Thin areas above 2,500ft. 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.
Clouds are expected to move in Friday, with some sunny breaks Saturday. Temperatures will be warming up slowly over the next few days, and north winds will decrease. Clouds and some light rain/snow are possible Sunday.
|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
|59″||0″ / 0.00||0″ / 0.00||3,000||mod, N||0″/ 0.00 *|
Flower Mountain @ treeline
|44″||0″ / 0.00||0″ / 0.00||3,000||light, NW||0″/ 0.00*|
Chilkat Pass @ 3,500ft
|22″*||0″ / 0.00 *||0″ / 0.00*||3,000||mod, NW||0″/ 0.00 *|
( *star means meteorological estimate )
Additional Info & Media
If you get out on the snow, send in your observations!