|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.
Normal caution is advised in the backcountry today. There has been no new avalanche activity for the past 4 days. The latest activity was between February 26 and 28th when a warm-up and 0.2″ of rain triggered several small wet loose avalanches and, in the periphery of the forecast zone, a few wet slab avalanches. This warm-up capped our pack with a 1-4+” inch crust and began a several day melt-freeze cycle. With cold temperatures and cloud cover today, the pack will remain locked-up and frozen.
In anticipation of snowfall this week, it’s important to take inventory of the surface conditions. Above the melt-freeze crust that caps the snowpack is a healthy layer of surface hoar which formed two nights ago (photo below and more details HERE). This is an ideal weak layer/bed surface combination and something to watch for if more than just a few inches of snow accumulates in the next few days. For today however, there is not enough snow in the cards.
Pictured below: widespread 5mm surface hoar over a crust – Todd’s Run (3,600′, NNW)
Additional concern to consider at upper elevations (4,000′ and higher):
Persistent slabs in steep high elevation terrain on the periphery of the forecast zone and in outlying areas. We have a generally poor snowpack structure at this elevation. 1-3′ below the degrading surface crusts is a weak layer of facets sitting on, and in between, the January crusts. These faceted layers have not been reactive of late but still exist. It will be remotely possible to trigger an avalanche in very steep terrain.
Yesterday’s cooling temperatures, shifting winds and mid-level clouds were the first sign of a change in the weather. During the past 24-hours temperatures have averaged in the low 20’s at the ridgetop weather stations and are sitting in the teens this morning. Winds have shifted from the Northwest to the Southeast overnight and continue to be light around 5mph.
A cold front is sliding down for the Northeast and joining with a weak low centered over us currently. Very light snow showers are in the forecast for today into Thursday. Only around a trace to an inch is expected by this evening. Temperatures look to remain in the teens on the ridgetops and near 30F at 1,000′ (cold enough that snow might make it to sea level). Winds are expected to pick up slightly to 10-15mph from the Southeast.
Beginning late tonight and through Wednesday we should see temperatures remain just cold enough for snow to sea level with 2-5″ possible. Snow should taper off Thursday. Stay tuned.
A few snowpack and water #’s – as of March 1st from the Turnagain Pass SNOTEL at 1880′ elevation on Center Ridge:
Snow depth: 42″, this is 47% of average…ouch (Only 10 years of data exist so far, 2005-2014)
Precipitation (graph below): 86% of average (due to rain in October and January)
SWE (graph below): 50% of normal for the median SWE
|Observation: Seattle Ridge
|John Sykes Forecaster
|Observation: Kickstep NE Bowl
|Observation: TinCan Backdoor/ Center Ridge
|AAS L1 Turnagain
|Avalanche: Lynx Creek
|Observation: Turnagain, Seattle, Mt Ascension
|Silverton Mountain Guides
|Observation: Tincan Trees
|Dalpes/Thamm/ Schauer Forecaster
|Observation: Seward Highway across from Johnson Pass TH
|Avalanche: Base of Seattle Ridge
|Troy Tempel, Thomas Lees, .Josh Bollaert, Damian Naquin