The avalanche danger will be MODERATE today for new winds slabs, 4-6" thick, on NW to NE aspects, at upper elevation, on slopes steeper than 35º. The avalanche danger today will be LOW in the morning, rising to MODERATE in the afternoon for wet avalanches. Human triggered avalanches will be possible at low and mid elevations, on steep slopes greater than 40º, on mostly SE to W aspects. Cornice fall will be possible on leeward aspects today.
A solid overnight freeze will make for firm and challenging travel at most elevations in the morning until warmed by the sun and rising afternoon temps. Ski crampons and/or cursing might increase your enjoyment this morning.
Cornices are still large and unpredictable, give them a wide berth. Winter is back, if only for a moment, so get out and enjoy it!
Problem 1: Wind Slab
Moderate wind gusts, SSE 13-21 mph on 4/12 combined with about 4” inches of new snow will make it possible to human trigger a new wind slab today 4-6” thick on NW to NE aspects at upper elevation, on slopes 35º and steeper. New wind slabs will be sitting on old faceted surfaces and will not bond well. Expect small avalanches in specific areas, up to D1 in size. It will be possible in very isolated locations for a small wind slab to initiate a larger dry loose sluff, if you are lucky enough to find the hidden square powder. Assessing this hazard and good terrain management will be key to avoiding this problem.
Problem 2: Wet Loose
Strong sunshine today combined with 4” inches of new moist snow (frozen overnight) will make small human triggered wet loose sluffs possible on steep slopes, on mostly SE to W aspects, at low and mid elevation, in the afternoon. Small loose dry sluffs may be possible at upper elevation on solar aspects once the sun hits.
A solid overnight freeze will keep avalanches small and will not be enough to raise your neck hairs over deeper crusts softening and contributing to a larger avalanche problem.
Fortunately, the snowpack gives us clues when the it becomes wet enough to be a problem. Rollerballs, and wet soggy snow are red flags for when to move to shadier aspects and cooler terrain.
Problem 3: Cornice
Cornice failures are unpredictable and a high consequence hazard. We can reduce our exposure to this hazard by limiting time spent under or near this hazard. Avoid uptracks with cornices above. While traveling on ridgelines, cornices may fail further back from the edge of slopes than expected, and may pull out adjoining snow. Cutting cornices is not recommended as a stability testing tool, as the hazards associated with cutting them are greater than the value of the information we may gather.
More about avalanche problems in the avalanche problem toolbox, HERE.
PREVIOUS ADVISORIES AND UPDATES HERE
Avalanche activity has been kept to a minimum due to a significant cooling trend for most of the week, especially above 3000'. Warm days didn't get quite warm enough to produce noticable wet avalanches. Winter returned Friday, bringing up to 4 inches of new snow to HP. Due to poor visibility Friday, no avalanches were observed. It is likely that small natural wet avalanches occurred on Friday before a solid freeze overnight.
More avy activity HERE on the mid-week summary . Thanks Sam and Jessie for providing this valuable asset to HPAC this season!
For more info and pictures on the Natural and Human triggered avalanches this week , check out weekly OBSERVATIONS HERE.
This week’s weather at Independence Mine 3550′:
Temps averaged 28ºF, with a low of 24ºF and a high of 42ºF.
3-5" of new snow since Tuesday.
Overnight at 3550′:
Temps averaged 24°F.
No new snow overnight.
This week’s weather at Marmot Weather Station 4500′:
Temps averaged 27ºF, with a low of 22ºF and a high of 39ºF.
Winds averaged ESE 7 mph, max 18 mph . Gusts averaged ESE 12 mph, max gust ESE 41 mph.
Overnight at 4500′:
Temps averaged 19ºF overnight.
Winds averaged SE 4 mph overnight. Max gust SE 7 mph.
NWS Rec Forecast HERE
NWS point forecast HERE
State Parks Snow Report and Motorized Access information HERE
A solid overnight freeze will keep avy activity to a minimum today. Expect clear skies, sunshine, and cooler temps throughout the weekend.
Read entire HPAC advisory HERE.
This is the last avalanche advisory of the season, but for those of you not willing to put the skis away yet, keep those observations coming! Thank you for a great season. If you haven't had a chance to support your local avy center, please consider DONATING today to help the coffers for next season. Best way to DONATE is directly to HPAC either via Facebook or HERE. Thank You!
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