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Hatcher Pass received a rapid load of 10 inches of new snow in about 10 hours on Saturday and .5″ SWE at 3500′. The storm was accompanied by wind SSE 10-15 G 16-22 for 7 hours at 4500′. It will be possible to human trigger a wind slab, storm slab, wet-loose, dry-loose, or a deep persistent slab avalanche today. Whumping and cracking were observed Saturday at low to mid elevation. We anticipate that natural avalanches occurred during the storm Saturday. Avalanche hazard is expected to decrease within 24-48 hours of the storm.
See Saturday’s Forecast for more information.
Travel Advice | Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. | Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. | Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential. | Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. | Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain. |
Likelihood of Avalanches | Natural and human-triggered avalanches unlikely. | Natural avalanches unlikely; human-triggered avalanches possible. | Natural avalanches possible; human-triggered avalanches likely. | Natural avalanches likely; human-triggered avalanches very likely. | Natural and human-triggered avalanches certain. |
Avalanche Size and Distribution | Small avalanches in isolated areas or extreme terrain. | Small avalanches in specific areas; or large avalanches in isolated areas. | Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. | Large avalanches in many areas; or very large avalanches in specific areas. | Very large avalanches in many areas. |
Signal Word | Size (D scale) | Simple Descriptor |
Small | 1 | Unlikely to bury a person |
Large | 2 | Can bury a person |
Very Large | 3 | Can destroy a house |
Historic | 4 & 5 | Can destroy part or all of a village |
Storm slabs will be possible to trigger on all aspects at all elevations today 6-12″ deep. This problem is anticipated to heal quickly.
Signal Word | Size (D scale) | Simple Descriptor |
Small | 1 | Unlikely to bury a person |
Large | 2 | Can bury a person |
Very Large | 3 | Can destroy a house |
Historic | 4 & 5 | Can destroy part or all of a village |
Winds slabs will be possible to trigger today on NW to NE aspects at upper elevation where winds transported 10″ of new snow. Expect wind slabs 10-16″ deep. Winds slabs should heal quickly within 24 hours.
Signal Word | Size (D scale) | Simple Descriptor |
Small | 1 | Unlikely to bury a person |
Large | 2 | Can bury a person |
Very Large | 3 | Can destroy a house |
Historic | 4 & 5 | Can destroy part or all of a village |
Deep persistent slabs up to 5 feet deep will be possible to human trigger today with an additional load of 10″ of new snow 3/21. Although we haven’t seen activity on this layer in 5 days, there is still concern for this low probability/high consequence problem. It will be possible to trigger deep persistent slabs this weekend, on all aspects, at all elevations and most likely on E to W aspects up to 3800′.
Larger loads like snowmachines and cornice failure will have higher chances of triggering an avalanche. Lighter loads such as a person on foot will be able to trigger this problem in specific locations where the slab component is thinner and the buried weak layer is closer to the surface.
Poor structure in snowpack will continue to be a problem through this season. With additional daylight hours, solar gain and increased temperatures, this weak layer may keep rearing its head.
Small wet-loose sluffs will be possible to human trigger today at low and mid elevation on southerly slopes, SE to SW, on steep slopes in the afternoon. If the sun does shine as predicted and temperatures rise into the 30’s, wet-loose will increase in size. Rollerballs are a good indicator to get off the slope and head to cooler, shadier terrain.
DRY-LOOSE
16″ of new snow since 3/17 will increase the hazard for dry loose today in specific areas. Dry loose sluffs will be possible to trigger on steep northerly aspects today in wind sheltered terrain, at upper elevation where the snow remains cool. Sluff management will be a helpful tool for avoiding being carried somewhere you don’t want to go today.