Over the last 72 hours heavy snow has been falling above 2500′ with rain and mixed precipitation occurring below.  At upper elevations dense storm slabs exist 1 1/2-3 feet deep.  New snow is putting stress on a buried weak layer in our upper snowpack (see problem 2) creating a more dangerous setup than just a storm slab problem.  Recent new snow is heavier than the underlying snow creating an upside down (unstable) snowpack at the surface.  New snow will need time to bond with the snowpack.  In the meantime, human triggered avalanches 1-3 feet in depth will be likely on slopes steeper than 32°.  Convex and wind loaded terrain will be the most sensitive areas.

Stability will usually increases for heavy storm slabs once temperatures fall and moisture starts to be drawn out of the snowpack.  This is not expected to occur anytime soon.  A persistent weak layer exists as well as unusual weather is forecasted for the weekend that will bring sunny skies and above freezing temperatures at upper elevations (up to 5000′).  

  Below 2500′ human triggered wet loose avalanches will remain likely until temperatures fall below the freezing mark.  On 1/25  16 inches of new snow was found to be very wet (saturated).  Above 2500′ new snow was moist and showed easy failure at the new/old interface in stability tests.

The amount of new snow we have received along with above freezing temperatures below 2500′, is enough to elevate the avalanche hazard on its own.  When you involve a buried persistent weak layer like we currently have, our upper snowpack becomes significantly more dangerous.  The 24 hour rule does not apply to our current setup.  Human triggered avalanches remain likely 1-3 feet in depth.

At this point it is unclear as to where the 1/14 buried surface hoar layer will remain a problem.  On 1/25 it was identified 2 feet deep at 3000′, but was not found to be reactive in both ECTs and PSTs.  At this location rounding was occurring and it was mixed with other rounded grains as it is being absorbed into the snow below.  It is possible that the saturated storm snow below 2500′ has removed this problem at low elevations and in the Maritime climate zone.  Above 2500′  it is very possible that this persistent weak layer remains reactive.  It will be important to try to identify this layer and test its sensitivity in areas that you choose to travel. This is best done through digging snowpits,  although confusing or misleading results can occur.  Conservative terrain choices are advised moving forward.

Weak snow exists near the base of our snowpack in all three climate zones.  The weather we are currently experiencing is putting these weak layers to the test and the likelihood of natural or human triggered avalanches has gone from unlikely to possible.  It is unclear how much weight (rain or new snow) these layers can accept before failing.  Realize if these layers do reach the tipping point very large avalanches would be the outcome.  Significant weather that we are currently experiencing is when deep avalanches generally occur.  The best mitigation technique, is avoidance of large avalanche terrain while a test of the snowpack is underway.

Rounding facets near the base of our snowpack from Cracked Ice at 4000′ on 1/11.