Avalanche forecast

Mount Shasta

Mount Shasta Avalanche Center
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Avalanche danger

Tue
Alpine
4 · High
Treeline
3 · Considerable
Below
2 · Moderate
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Highlights

Dangerous avalanche conditions will develop today.  Heavy snowfall and sustained winds continue to impact the area and build storm slabs across upper-elevation terrain.  Sticking to wind-sheltered areas below treeline, avoiding slopes above 35 degrees in steepness, and staying out from underneath large, steep slopes will decrease exposure to avalanches if traveling in the backcountry today.

Avalanche problems

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely
    Size
    1–2.5

    The forecast zone has received 12-22" of snow and 1-1.5" of snow water equivalent in the past 36 hours.  Forecasts show another 16-25" of snow and 1.5-2" of water today, with peak precipitation in the morning.  This storm came in relatively cold near and above treeline and the temperature trend has been increasing, so there may be denser snow over lighter snow, which can create unstable slabs.  Old snow surfaces were cold, firm, and icy in places, and good bonding between the old and new snow is suspect.  Assess how the new snow is bonding to the old snow surface, and be skeptical of "upside down" snowpack structures where low density snow is overlayed by heavier, denser snow.  Cracking, collapsing, and shooting cracks are signs of instability and avalanche potential.  Heavy snow accumulations and sustained wind mean natural avalanches could run far today, so avoid the runouts underneath large avalanche paths.  

  • Wind Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–2.5

    Moderate to strong winds from the S-SW-WSW have, and will continue to, form deeper slabs on leeward (downwind) slopes facing NW-N-NE-E.  These slabs can be denser than the storm snow and shaped like lenses or pillows.  Cornices (overhanging lips of snow) are indicators of wind-loaded slopes on their downhill side.  Shooting cracks and hollow, drum-like sounding snow are also indicators of wind-slabs.  Avoid these slopes today, and any terrain that is underneath them.

Avalanche Discussion

Some uncertainty exists about storm-snow bonding, wind-loading patterns, and recent avalanches due to lack of field observations.  But anytime there is a lot of heavy snow and wind in a short time period, there is increased potential for avalanche activity.  The most dangerous areas where you will be able to trigger an avalanche will be below ridgelines on leeward aspects facing NW-N-NE-E.  Winds will have drifted more snow onto these slopes and slabs will be deeper, harder, and more cohesive.  Large natural avalanches above treeline are also likely. Today is not a good day to venture into the alpine.  Recreating below treeline will be safer, but watchout for rocks, stumps, and logs, as this area was mostly bare ground before this storm.  

The county has closed the gate at McBride Springs along the Everitt Memorial Highway, as well as the road to Castle Lake.  Please give crews room to work and do not park in front of the gates.  If walking on the road , keep your eyes and ears open for plow trucks and get out of the way! 

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