Northern San Juan

Avalanche

Bill Nalli Chris Bilbrey · Feb 16, 2020 · Northern San Juan

Weather

Intermittent very light snowfall began early afternoon with only a trace accumulated by 3:30pm. Periiods of gusty winds and loss of visibility followed by clearing. After dark snowfall picked up to S-1

Snowpack

The state of the snowpack in this portion of the San Juan Mountains is more similar at present time to the South San Juan zone verus locations north of Lizard Head Pass. The snowpack is deep and strong in many alpine locations. Isolated pockets of wind-drifted slabs exist along ridge tops and on steep sidewalls of gullies in the alpine. They rest above weaker faceted snow but remain hard to trigger currently until they get another significant load above. Many sun exposed slopes have a slick, hard crust on the surface that will not allow good bonding with incoming snow. The near treeline zone harbors softer surface conditions with surface faceting found on northerly and easterly-facing slopes. Below treeline the snow surface continues to deteriorate on northwest through northeast to east wherever sheltered from the sun. Below about 10,500 feet, the snowpack is taking on a spring like regime. Successive melt/ freeze cycles has left a strong frozen pack. With each warming cycle, snow depths continue to decreasing and snow cover extent is diminishing as well. Southeast and east aspects at higher elevations harbor concerning crust/ facet layers near the surface that are stout enough to support a bigger load before failing. By mid-afternoon, strong southwest winds were starting to transport snow onto leeward slopes but snow available to move in fetches has been limited from recent winds and warm temperatures. This could develop into a new avalanche problem with snowfall in the forecast.

Avalanche

More evidence of D2 avalanches from our early February natural cycles above treeline.