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Avalanche Advisory for 2018-03-12 07:03

  • EXPIRED ON March 13, 2018 @ 7:03 am
    Published on March 12, 2018 @ 7:03 am
  • Issued by Andrew Kiefer - Mt Shasta Avalanche Center

A potent storm will begin this afternoon. Heavy rain and snow are expected tonight and tomorrow with snow levels ranging between 6,500-8,000 ft. The avalanche danger will rise over the next 24 hours as wind slabs develop above treeline.

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

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

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

Avalanche Problem 1: Wind Slab

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

Strong southerly winds accompanying the storm will create wind slabs above treeline on leeward slopes. Wind slab development will occur late in the afternoon and overnight. Wind slabs will grow in size and distribution as the storm progresses. As snow begins to accumulate today, watch for blowing snow, cornices/wind lips, textured snow surfaces and hollow sounding snow as evidence wind loading has occurred.  

Advisory Discussion

The bulk of precipitation will come between 11 pm tonight through 5 pm tomorrow. Avalanche danger will rise to MODERATE late this afternoon and overnight as wind slabs develop. Storm slabs will likely become a problem tomorrow as a rapid load of new snow is added to our snowpack. The rain/snow line will be as high as 8,000 ft during the storm. Rain may melt much of our existing low elevation snowpack, while several feet of snow expected near and above treeline will create dangerous avalanche conditions tomorrow.

Recent Observations

Spring-like weather brought warm temperatures and sunshine yesterday. Highs in Mount Shasta City hit 62 degrees and the mid 40s on Grey Butte at 8,000 ft. Light winds blew out of the SE in the afternoon but ramped up overnight with gusts to 30 mph near treeline. No avalanche activity has occurred over the past week. Shallow snowpack hazards still exist in all zones throughout the advisory area. The Pilgrim Creek Snowmobile Park trails have recently been groomed.

Weather and Current Conditions

Weather Summary

A strong frontal system will impact the area tonight through Tuesday bringing heavy rain and snow. Skies will remain clear this morning with increasing cloud cover throughout the day. Highs will be in the mid 40s and south winds will become strong this afternoon and overnight. Precipitation should begin after 5pm, with the bulk of rain and snow expected overnight and during the day tomorrow. Snow levels will be high ranging between 6,500-8,000 ft over the next 48 hours. The advisory area should receive over 2 inches of water by Wednesday morning. This should translate to 18-24 inches of snow for upper elevation terrain. Precipitation will continue through the end of the week.

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) 32 27 62 45 1 N
Sand Flat (6750 ft)
Ski Bowl (7600 ft) 31.5 26.5 42.5 34.5 61.5 0 0 .5
Gray Butte (8000 ft) 30 28 41.5 33.5 8 25 E station down
Castle Lake (5870 ft) 31.5 31.5 31.5 31.5 27 0 0
Mount Eddy (6509 ft) 34 25 45 36.5 2 9 WSW 41 0 1
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
  Monday Monday Night Tuesday
Weather Rain and snow likely after 11am. Chance of precipitation 70% Heavy rain and windy. Chance of precipitation 100%. Rain and snow, becoming all snow after 11am. Windy with a chance of thunderstorms.
Temperature (°F) 39 37 35
Wind Direction S S S
Wind Speed (mi/hr) 10-15 mi/hr 10-15 mi/hr 10-15 mi/hr
Expected Snowfall (in) < .5 0 5-9
For 9000 ft to 11000 ft
  Monday Monday Night Tuesday
Weather Snow mainly after 11am. Windy. Heavy snow and windy Snow. The snow could be heavy at times. Slight chance of thunderstorms.
Temperature (°F) 26 25 20
Wind Direction S S S
Wind Speed (mi/hr) 25-35 mi/hr 35-45 mi/hr 35-45 mi/hr
Expected Snowfall (in) 2-3 5-8 18-24

Season Precipitation for Mount Shasta City

Period Measured (in) Normal (in) Percent of Normal (%)
From Oct 1, 2017 (the wet season) 12.52 32.15 39
Month to Date (since Dec 1, 2018) 1.63 2.65 62
Year to Date (since Jan 1, 2018) 6.69 16.94 39


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.