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Avalanche Advisory for 2017-12-31 06:50:25

  • EXPIRED ON January 1, 2018 @ 6:50 am
    Published on December 31, 2017 @ 6:50 am
  • Issued by Andrew Kiefer - Mt Shasta Avalanche Center
  • December 31, 2017 @ 6:50 am

    Advisory Hotline: (530) 926-9613

  • LOW avalanche danger and normal caution continue. Generally safe avalanche conditions exist. Sparse coverage and firm and icy slopes present significant travel hazards in the backcountry. 

  • Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Avalanche Problem 1: Normal Caution

  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Very Likely
  • Size ?
    Very Large

Normal caution is advised. The firm, icy, and thin snowpack continues to create backcountry travel hazards. Moving through steep terrain above treeline is challenging and dangerous. Arresting a fall in these conditions would be difficult. Watch out for rocks. Low angle slopes with smooth ground cover offer the best skiing and riding conditions.

  • Ski and ride one at a time in avalanche terrain.
  • Don’t regroup in run-out zones.
  • Avalanche rescue skills are always essential when you travel in avalanche terrain.

Advisory Discussion

For several days, clear and warm weather conditions have remained steady, and our snowpack has experienced very little change. A re-cap of our season: October and November storms laid a shallow snowpack at high elevations on Mount Shasta. During Thanksgiving week, it rained up to 10,000ft. This rain event was followed by cold and clear weather which capped the snow surface at 7,000ft and above with a crust, while below, it eliminated any existing snow on the ground. We have had two small storm events this December totaling 10 inches of snow and less than 1 inch of water. Otherwise, high pressure has dominated our weather pattern. Precipitation is well below average, and a large portion of our advisory area is free of snow. Mount Shasta and Ash Creek Butte are the only areas with a (barely) usable snowpack. 

Recent Observations

The snowline slowly creeps upward. Very little coverage exists below 6,500ft. The height of snow ranges from 30-100cm between 6,500-9,500ft. The rain crust that formed on Thanksgiving continues to lock up the lower snowpack. This slick, icy layer is the primary snow surface near and above treeline. On north and east aspects below treeline, 20-25cm of recycled powder (the December 3rd and December 20th storms) exists at the snow surface.  On south and some west aspects, near and above treeline, patches of corn snow can be found. Snowpack stability is very good throughout the advisory area. Rocks, down trees, small tree tops and bushes are widespread.

Weather and Current Conditions

Weather Summary

A quiet weather pattern will finish off December and bring in the New Year on a dry note. Weak temperature inversions continue. Partly cloudy skies are expected today and tomorrow with high temperatures reaching the mid 40s to lower 50s. Southerly winds will blow at light to moderate speeds. Very low chances for precipitation begin on Tuesday and last through the week. Freezing levels should remain high during this time. At best, terrain above treeline will receive light snow flurries. More substantial chances for precipitation begin Thursday, but don’t get your hopes up. Warm temperatures will continue through the end of the week. Quite a bit of uncertainty exists regarding the long term forecast.

CLICK HERE for information from the NOAA Climate Prediction Center


THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 5.83 inches of water, normal is 14.96 inches, putting us at 39% of normal. For the month of December, we have received .29 inches of water, normal is 7.60 inches, which is 4% of normal. And finally for the year of 2017, we received 44.82 inches of water, normal is 42.96 inches, putting us at 104% of normal.

Always check the weather before you attempt to climb Mt Shasta. Further, monitor the weather as you climb. Becoming caught on the mountain in any type of weather can compromise life and limb. Be prepared.

24 Hour Weather Station Data @ 4:00 AM

Weather Station Temp (°F) Wind (mph) Snow (in) Comments
Cur Min Max Avg Avg Max Gust Dir Depth New Water Equivalent Settlement
Mt. Shasta City (3540') 36 34 53 41 1 N
Sand Flat (6750') 34 33 46 38 15 0 0 0
Ski Bowl (7600') 37 34 43 39 19 0 0 0
Grey Butte (8000') 36 35 41 37 16 43 WNW
Castle Lake (5870') 43 39 48 42 9 0 0 0
Mount Eddy (6509') 39 35 41 38 2 3 W 10 0 0
Ash Creek Bowl (7250') station down
Ash Creek Ridge (7895') station down

Two Day Mountain Weather Forecast

For 7000 ft. to 9000 ft.
  Sunday Sunday Night Monday
Weather Mostly Sunny Mostly Cloudy Partly Sunny
Temperatures 46 deg. F. 39 deg. F. 47 deg. F.
Wind direction South South/Southeast South
Wind speed 5-10 mph 5 mph 0-5 mph
Expected snowfall 0 in. 0 in. 0 in.
For 9000 ft. to 11000 ft.
  Sunday Sunday Night Monday
Weather Mostly Sunny Mostly Cloudy and Breezy Partly Sunny
Temperatures 31 deg. F. 26 deg. F. 29 deg. F.
Wind direction South/Southwest South/Southwest Southwest
Wind speed 15-20 mph, gusting 25 mph 20-25 mph, gusting 30 mph 15-20 mph, gusting 30 mph
Expected snowfall 0 in. 0 in. 0 in.


This advisory does not apply to Ski Areas or Highways and is for the Mount Shasta, Castle Lake and Mount Eddy backcountry. Use this information for guidance only. You may find different conditions in the backcountry and should travel accordingly. This advisory expires on midnight of the date it was posted unless otherwise noted.