You are here

Avalanche Advisory for 2018-01-21 07:01:45

  • EXPIRED ON January 22, 2018 @ 7:01 am
    Published on January 21, 2018 @ 7:01 am
  • Issued by Andrew Kiefer - Mt Shasta Avalanche Center
  • January 21, 2018 @ 7:01 am

    Advisory Hotline: (530) 926-9613

  • MODERATE avalanche danger exists near and above treeline. Watch for fresh wind slabs above 8,000ft on S-SE-E-NE-N aspects. A winter storm will begin this morning and avalanche danger is expected to rise this afternoon and by tomorrow. Monitor changing conditions throughout the day.

     

     

  • Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Avalanche Problem 1: Wind Slab

  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Snowfall and strong westerly winds will create fresh wind slabs near and above treeline on S-SE-E-NE-N aspects. Human triggered wind slab avalanches will be possible on leeward slopes and terrain features 35 degrees and steeper above 8,000 ft. Watch for new wind slab development throughout the day as winds increase and snow accumulates. Wind slabs could be 1-3 ft thick. In specific wind loaded areas, it will be possible to trigger a wind slab by the end of today that could be large enough to bury, injure, or kill a person.  

 

 

Advisory Discussion

The storm today will bring snowfall, strong westerly winds, and cold temperatures. Snow forecasts have downgraded right before show time once again. However, the new snow and wind will likely create increasing avalanche danger late this afternoon and overnight. Pay close attention to the obvious signs of wind slab development: blowing snow, cornice formation, wind pillows, hollow sounding snow and textured snow surfaces.

Recent Observations

Clear and cold weather made for a gorgeous morning yesterday. Patchy clouds began to move in around 11am, but periods of sunshine continued throughout the afternoon. Overnight, winds shifted to the west averaging 10-15 mph with gusts to 25 mph at 8,000 ft. A trace amount of snow accumulated yesterday, and our recent storm snow has settled 1-2 inches. Snow surfaces have remained cold and dry. Above 9,000 ft, winds have been transporting snow onto S-SE-E-NE-N slopes and scouring ridgelines and exposed terrain features down to a slick icy surface. No avalanches have been observed or reported in several days.

Weather and Current Conditions

Weather Summary

The NWS has issued a Winter Storm Warning in effect until 1AM Monday. A cold front is approaching the coast and will bring strong westerly winds and low elevation snowfall today. The bulk of precipitation will come between 10am-10pm, with lingering snow showers overnight. By Monday morning, the advisory area should receive .4 inches of water with snow levels staying at or below 4,000 ft. For areas 6,000 ft and above, expect 3-7 inches of snow for today, with an additional 3-6 inches tonight. High temperatures in the mountains will be in the low 20’s today with strong westerly winds. The cold front will move out of the area tonight, and a warming trend will be associated with the tail end of the storm. Monday should be dry. Another strong cold front will affect the area Tuesday night and Wednesday.

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) 29 27 42 32 2 N
Sand Flat (6750 ft) 19 14 26 19 16 1 0 0
Ski Bowl (7600 ft) 20 13 26 19 30 1 .1 1
Gray Butte (8000 ft) 16 14 25 18 6 25 WNW
Castle Lake (5870 ft) 25 20 28 24 3 0 0
Mount Eddy (6509 ft) 20 16 26 21 2 4 VAR 15 0 2
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
  Sunday Sunday Night Monday
Weather Snow, mainly after 10am. Chance of precipitation 100%. Wind chill values as low as -8 degrees F. Snow showers. Chance of precipitation 100%. Wind chill values as low as -8 degrees F. Temperatures rising to 29 degrees by 4am. Snow showers likely, mainly before 10am. Mostly cloudy.
Temperature (°F) 17 13 31
Wind Direction South South South/Southeast
Wind Speed (mi/hr) 15-25 mph 20-25 mph 10-15 mph
Expected Snowfall (in) 5-9 3-7 < 1
For 9000 ft to 11000 ft
  Sunday Sunday Night Monday
Weather Heavy snow and windy, mainly after 10am. Chance of precipitation 100%. Wind chill values as low as -18 degrees F. Snow showers between 10pm-4am. Windy. Chance of precipitation 100%. Wind chill values as low as -18 degrees F. Temperatures rising to around 21 degrees by 4am. A 50% chance of snow showers mainly before 10am. Mostly cloudy. Wind chill values as low as -10 degrees F.
Temperature (°F) 12 10 20
Wind Direction West/Southwest West/Southwest West
Wind Speed (mi/hr) 30-40 mph, gusting 50+ mph 30-40 mph, gusting 50+ mph 25-35 mph
Expected Snowfall (in) 6-10 5-9 < 1

Season Precipitation for Mount Shasta City

Period Measured (in) Normal (in) Percent of Normal (%)
From Oct 1, 2017 (the wet season) 8.64 19.91 43
Month to Date (since May 1, 2018) 2.81 4.70 60
Year to Date (since Jan 1, 2018) 2.81 4.70 60

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.