This advisory expires 24 hours from posting.

BOTTOM LINE:

The avalanche hazard is MODERATE. Human-triggered avalanches are possible and natural avalanches are unlikely. Small avalanches are possible in specific areas, including roll overs, ridge features, and thin zones where it is more likely to hit the “weakspot” in the snowpack and trigger the persistent slab that is sitting on old buried surface hoar.

Our two week surface hoar cycle has finally taken a break from all the activity. However, buried surface hoar still exists beneath the new wet crust and/or wind slab. Expect the new crusts to continue to insulate the buried weaker cold layers, ie..surface hoar, facets, and near surface facets, until the temperature warms. These weaker buried layers will be excellent sliding layers as the upper layers of the snowpack warm up enough to sluff and/or become more slab-like over the next few weeks. As the sun continues to shine and the snow softens, don’t forget what is down deep and waiting to wake up. The shift to spring, and therefore, the shed cycle will be more tame if the temperature increases slowly. However, if temperatures take a sudden jump to no pants weather, expect a more severe and dramatic shed cycle. In any case, paying attention to your aspect and the time of day will help to avoid triggering a sluff, slab, or getting swept away by one.

Click here for a description of low, moderate, considerable, high and extreme hazards using the North American Avalanche Danger Scale.

AVALANCHE CONCERN #1:

The persistent slab sitting on top of old buried surface hoar was incredibly active for more than 2 weeks.  Our persistent layer concern still exists, although now it is covered by a couple inches of new wet snow and a 1-3″ thick wind slab from Wednesday and Thursday winds that gusted between 25-45mph. At this point, most aspects have either a wind, sun, or melt-freeze crust, many of which are sitting on near surface facets, on top of the persistent slab on surface hoar.  Pay attention to these layers as spring conditions dictate the future of the snowpack.

AVALANCHE CONCERN #2:

Night time temperatures continue to stay below freezing and daytime temps are starting to rise above freezing.  Wet-loose avalanches have been observed on south, west, and east aspects. Most of these sluffs are originating near rocks that heat up in the mid-day sun. Wet-loose avalanches can originate from any weak layer location in the snowpack, and can be significant enough to entrain enough snow to bury, injure, or kill a person. At this point, wet-loose avalanches range from 8-12″ deep, which are small enough to pull you off your feet and twist a knee. However, if spring actually comes as expected this year, wet-loose avalanches will gain momentum, mass, and move you where you don’t want to go.  Steer clear of any slope with soft wet snow deeper than 6″. Although wet-loose avalanches are the main concern, the possibility exists for wet-slab avalanches up to 12″ thick to pull out.  Stay out of terrain traps, especially at low elevations as the snow turns isothermal.  An isothermal snowpack will be the primary contributor to the shed cycle.

ADDITIONAL CONCERN:

Looming cornices continue to hang onto ridgelines waiting for warmer weather to detach themselves.  Cornices will lose their integrity and strength as they heat up during the day.  Cornice failure will most likely take us by surprise because the warm spring weather is yet to come.  Choose routes wisely and give cornices a wide berth of safety.

TREND: Increasing stability as temperatures stay cool.  Decreasing stability in the afternoon as southerly aspects heat up. Decreasing stability as soon as temperatures stay above freezing at night.

-Thanks for a great season. Enjoy the snow into summer!

Have a safe weekend,
Allie Barker

If you are out and about HP and see an avalanche or have a snow observation, please share it with us by clicking on the links under observations, or email us at info@hatcherpassavalanchecenter.org