Monthly Archives: March 2012

Saturday, March 24, 2012

This advisory expires in 24 hours

BOTTOM LINE:

Natural avalanches are very unlikely and human triggered avalanches are unlikely at mid and high elevations on all aspects. Natural avalanches are unlikely and human triggered avalanches are possible on south aspects at low elevation.

TREND:

Stable on most aspects.

Deteriorating stability on south aspects at low elevation during the heat of the day.

DISCUSSION:

The amount of tracks at Hatcher Pass right now could fool just about anyone into thinking a ski resort was nearby. The number of tracks and the absence of significant natural and human triggered avalanches shows the long withstanding stability trend we have endured over the past month. Conditions continue to range from windslab, to sun crust, to facet powder, and a mix of all of the above. Between 3/23 and 3/24 wind speed picked up enough to develop a wind crust/slab varying from 1-5″ thick on exposed north, east and west aspects. Wet loose point releases have been observed in greater numbers on south aspects at low elevation during the heat of the day.

Due to a cooler March, we have yet to see significant heating and a true “shed cycle” of the snowpack. Be warned, it is on the way. The stability of the snow and low energy has made us lazy by way of FACETS. (Familiarity, Acceptance, Consistency, Experts, Tracks, and Scarcity) These FACETS are heuristics that lead to poor decision and avalanche accidents. Being aware of them can keep you out of trouble. As the weather changes so must our perspective of the snowpack. New wet snow or rain and/or significant heating will dramatically change the structure and stability of the snowpack.

At this point our biggest concern lies on south aspects. Sun crusts and radiation crusts are growing in size and developing larger facets beneath the crusts. South aspects at low elevation are heating up enough for wet-loose point releases to become prime time. These avalanches are growing in size and number, and are large enough to throw you off your feet or week a knee. As the sun beats its blazing rays on the slopes wet-loose avalanches will become more likely.

The large gaping cornice crevasses continue to grow in size, weakening bonds to their slopes, and preparing for detachment as the sun’s radiation increases. Good hazard evaluation techniques should be used in conjunction with keeping a humble distance from the large cornice edge.  Cornices can be good stability indicators as they weaken, detach, and fall onto slopes beneath them. Watch to see if they trigger any sizable avalanches as they fall.

No dramatic changes have been observed on N,E, and W aspects. A new brittle wind slab 1-5″ thick exists on some north, northeast, and west aspects.  This wind slab varies in hardness and sits over large facets, however, the lack of energy in the snowpack has withheld key ingredients in the recipe for an avalanche. This slab is non-cohesive and brittle, however, the possibility of popping out a small slab exists on shallow faceted ridges, rollovers, and rocky zones, so choose lines wisely.

Paying attention to the rate of change as we blossom into spring will be tell tale of the avalanche cycles to come.

-Allie Barker