Southern San Juan

Avalanche

Chris Bilbrey · Mar 11, 2020 · Southern San Juan

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Weather

Obscured skies to start with S1 to S2 snowfall until around 2 pm. While driving north along 550 corridor, we hit the rain/ snow line at about 9,000 feet and freezing level was just shy of pass level. Southwest winds were generally light with periods of moderate gusts. By 3 pm, storm began to clear and skies transitioned to broken/ scattered. Brief periods of sunshine in the afternoon (approx. 30 minutes worth) kicked off lots of rollerballs and loose-wet sluffs all size 1 or smaller.

Snowpack

Around 5 to 6 inches has fallen in the last 24 hours with up to 10 inches accumulating since 3/8. Both storms events fell right-side-up and fairly dense (around 10% or possibly higher). We found good bonding between storm layers and as well, the underlying old snow surface. Deeper drifts along ridge tops that face northeast produced isolated cracking and a few audible collapses. Cracking was mostly confined to below our skis, but a few cracks shot outward around 10 to 20 feet. Very little sluffing of the new snow noted in steeper, treed terrain. A snowpit near treeline on a northeast aspect showed multiple near-surface facets layers in the top meter, but none produced propagating results in Extended Column Test. Those layers will become suspect and may turn reactive with a big new snow load in the coming days. The snowpack there was still dry and cold. Cooler temperatures over the past 24 hours contributed to another superficial refreeze of the upper snowpack at lower elevations. This re-frozen layer easily broke with boot penetration and poking around with a ski pole on multiple aspects. Lots of rollerballs and small loose-wet sluffs with a brief appearance by the sun. The new snow below treeline also started to set up and settle rather quickly from warmer temperatures in the afternoon - sticky and grabby.

Avalanche

Lots of rollerballs and small loose-wet slides on east-facing terrain from a quick shot of sunshine in the afternoon. All slides were size 1 or smaller and generally harmless. This could grow in size for tomorrow if sun and warm temperatures prevail.