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Mount Shasta Avalanche Advisory

  • Published on February 20, 2018 @ 7:00 am
    This Avalanche Advisory expires in 21 hours, 53 minutes
  • This advisory is valid for 24 hours
    Issued by Andrew Kiefer - Mt Shasta Avalanche Center
  • February 20, 2018 @ 7:00 am

    Advisory Hotline: (530) 926-9613

  • Avalanche danger is LOW and NORMAL CAUTION is advised. Firm and icy snow surfaces are widespread and shallow snowpack hazards exist. Minor wind loading has occurred on S-SE-E aspects between 7,500-9,000 ft. Watch for unstable snow on isolated terrain features.

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

Avalanche Problem 1: Normal Caution

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  • Likelihood ?
    Certain
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  • Size ?
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NORMAL CAUTION means:

  • Watch for isolated slabs.
  • Ski and ride one at a time in avalanche terrain.
  • Don't regroup in run out zones.
  • Basic avalanche rescue skills are essential in avalanche terrain.

Isolated slabs are related to wind and terrain. Look for areas of drifting snow. This will occur on the lee side of ridges, in terrain depressions, on convex terrain features, and in the lee of isolated bands of trees.

Advisory Discussion

Cold temperatures and wind chill values well below 0° F will continue today. Strong winds have stripped away the recent snow in terrain above 9,000 ft where the old and icy snow surface is exposed. Arresting a fall on a steep slope above treeline would be difficult in these conditions. Drifts of snow, miniature cornice formations and inconsequential wind slabs were found on southeasterly aspects between 7,500-9,000 ft yesterday. Shallow wind loading occurred in isolated areas but did not seem to pose a significant avalanche concern. Regardless, watch for unstable snow on obviously wind loaded terrain features today.

Recent Observations

A ride to the Old Ski Bowl yesterday revealed 2-3 inches of new snow between 7,000-9,000 ft. Above, evidence of the new snow was hard to find and snow surfaces were very firm and icy. Above 9,000 ft, the new snow has been stripped away and transported to lower elevations. Between 7,500-9,000 ft, drifts of snow and small cornice formations 12-18 inches deep were found in isolated areas on E and SE aspects. Inconsequential and small wind slabs 2-4 inches thick were found in the same isolated areas. It was surprising to see the amount of wind loading that occurred between 7,500-9,000 ft given the amount of snow that fell. Cornice formations on a small test slope were easy to break with the weight of a person (video). Active wind loading was not observed yesterday.

Weather and Current Conditions

Weather Summary

Expect increasing cloud cover throughout the day. Temperatures will reach the mid 20s at 6,000 ft while above treeline highs will be in the teens. Northwest winds will continue with gusts up to 25 mph above 8,000 ft.  A low-pressure system will impact the Pacific Northwest late tonight through Thursday. This storm will give Mount Shasta another chance for light snow showers down to town level with .04 inches of water and .5-1 inches of snow expected by Thursday.

Season Precipitation for Mount Shasta City

Period Measured Normal Percent of Normal
From Oct 1, 2017 (the wet season) 10.20 27.05 38
Month to Date (since Feb 1, 2018) 0.09 4.78 2
Year to Date (since Jan 1, 2018) 4.37 11.84 37

24 Hour Weather Station Data @ 6:00 AM

Weather Station Temp (°F) Wind (mi/hr) Snow (in) Comments
Cur Min Max Avg Avg Max Gust Dir Depth New Water Equivalent Settlement
Mt. Shasta City (3540 ft) 18 18 35 26 5 N
Sand Flat (6750 ft) 11 11 12 12 18 0 0 .5
Ski Bowl (7600 ft) 6.5 4 14.5 8.5 40 trace 0.03 .5
Grey Butte (8000 ft) 5.5 5 15 8 6 31 SE
Castle Lake (5870 ft) 9 9 22.5 14.5 7.5 0 .5
Mount Eddy (6509 ft) 7 6.5 15 10.5 3 14 SE 22.5 0 .5
Ash Creek Bowl (7250 ft) station down
Ash Creek Ridge (7895 ft) station down

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Today Tonight Wednesday
Weather Partly sunny Mostly cloudy then 50% chance of snow showers. A 50% chance of snow before 10am, then a chance of snow showers, mainly after 4pm. Partly sunny.
Temperatures 22 deg. F. 13 deg. F. 25 deg. F.
Wind direction W/NW S NW
Wind speed 5-10 mi/hr 5-10 mi/hr 5 mi/hr
Expected snowfall 0 in. < 1 in. 1 in.
For 9000 ft to 11000 ft
  Today Tonight Wednesday
Weather Cold and partly sunny. Wind chill values as low as -25. 50% chance of snow showers then partly cloudy. Wind chill values as low as -19. A chance of snow before 10am, then a slight chance of snow showers after 10am. Partly sunny and cold. Wind chill values as low as -20.
Temperatures 2 deg. F. 2 deg. F. 3 deg. F.
Wind direction W/NW W N
Wind speed 15-20 mi/hr 15-20 mi/hr 15-20 mi/hr
Expected snowfall 0 in. < 1 in. 1 in.

Disclaimer

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.