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Avalanche Advisory for 2017-03-21 06:46:45

  • EXPIRED ON March 22, 2017 @ 6:46 am
    Published on March 21, 2017 @ 6:46 am
  • Issued by Andrew Kiefer - Mt Shasta Avalanche Center

The avalanche danger is CONSIDERABLE above treeline and MODERATE near treeline.  New snow and strong southeast winds have allowed wind slabs to form in lee areas near and above treeline, with the most dangerous conditions in alpine terrain above 9000ft.  Snowfall will continue as freezing levels lower, and backcountry travelers should carefully evaluate changing conditions throughout the day.  LOW avalanche danger exists below treeline.     

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

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.

Avalanche Problem 1: Wind Slab

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

New snow and strong winds have formed wind slabs on leeward slopes and terrain features near treeline and above treeline.  The wind slab problem will most likely be encountered today in terrain 9000ft and above.  Moderate to strong winds have been steady from the southeast for the past 12 hours, but variable in direction for the majority of the recent storm series.  This has allowed for wind slabs to be possible on all aspects.  With additional snow, strong winds, and lowering freezing levels throughout the day, the wind slab problem will increase in distribution and size.  Watch for blowing snow and cornice formation as indications of wind slab development.  Avoid lee slopes 35 degrees and steeper where recent wind loading has occurred.



Advisory Discussion

Expect blizzard conditions with gusty southeast winds and low visibility today. Areas above 8500ft look to receive up to a foot of new snow by tonight, and the avalanche hazard may increase to CONSIDERABLE above treeline by this afternoon. As snow levels lower throughout the day, the distribution of the wind slab problem may extend to lee slopes near treeline as well. Dangerous avalanche conditions will exist in the backcountry by the end of the day.

Recent Observations

Mount Shasta remained in the clouds for the majority of the day yesterday. Precipitation was sporadic in the morning, and light rain fell up to 8000ft. Precipitation picked up around 3pm yesterday, and temperatures hovered near and just below freezing at the Old Ski Bowl overnight. Near treeline and below treeline areas out of Bunny Flat picked up 2-3 inches of wet snow in the past 24 hours. Observations from above treeline were limited. The Castle Lake and Mount Eddy areas saw only rain, and 1-2 inches of snowpack settlement.  Moderate to strong winds blew steadily out of the southeast at the 8000ft level and above.

Weather and Current Conditions

Weather Summary

Unsettled weather will continue today as two occluded fronts impact the area. The first front will bring heavy rain and snow this morning with freezing levels near 6500ft. Gusty, southeast winds will precede the second front set to arrive early this afternoon.  Thundershowers are possible.  Heavy precipitation will continue as freezing levels begin to lower to 5500ft tonight, and 5000ft by tomorrow.  The advisory area looks to pick up 1 inch of water by midnight.  Areas between 6000-7000ft look to receive 2-4 inches of snow today, while above 8500ft, 12 inches or more are expected.  Precipitation should continue through tomorrow evening.


In Mt Shasta City at 0500, we have a current temperature of 45 F.

On Mt Shasta (South Side) in the last 24 hours...

Sand Flat - 6,750 ft, the current temperture is 34 degrees F.  Temperatures have ranged from 32 F to 36 F.  Snow on the ground totals 98 inches with 2 inches of new snow.

Old Ski Bowl - 7,600ft. the current temperature is 31 degrees F.  Temperatures have ranged from 29 F to 33 F.  Snow on the ground totals 177 inches with 4 inches of new snow and .86 inches of snow water equivalent. 

Gray Butte - 8,000 feet, the current temperature is 28 degrees F. Temperatures have ranged from 28 F to 31 F.  Winds have averaged 10-20 mph with gusts to 35 mph, blowing primarily out of the south/southeast.

Mt Eddy Range (West side of Interstate-5)... 

Castle Lake - 5,800 feet, the current temperature is 35 degrees F. Temperatures have ranged from 33 F to 39 F. Snow on the ground totals 92 inches with no new snow and 1 inch of settlement due to rain on snow.

Mt Eddy - 6,500 feet, the current temperature is 33 degrees F. Temperatures have ranged from 31 F to 36 F. Snow on the ground measures 83 inches with no new snow and 3 inches of settlement due to rain on snow. Winds have averaged 1-3 mph with gusts to 14 mph, blowing out of the south/southwest.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 45.45 inches of water, normal is 33.88 inches, putting us at 134% of normal.  For the month of March, we have received 2.14 inches of water, normal is 4.38 inches, which is 48% of normal. And finally for the year of 2017, we received 24.29 inches of water, normal is 18.67 inches, putting us at 130% 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.

CURRENT CONDITIONS at Bunny Flat (6950 ft)
0600 temperature: 34
Max. temperature in the last 24 hours: 36
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 5-10 mi/hr
Maximum wind gust in the last 24 hours: 20 mi/hr
New snowfall in the last 24 hours: 2 inches
Total snow depth: 98 inches

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Tuesday Tuesday Night Wednesday
Weather Rain and snow showers becoming all snow after 11am. Some thunder is also possible. Chance of precipitation 100%. Snow showers and windy. Chance of precipitation 100%. Snow showers and breezy. Chance of precipitation 90%.
Temperature (°F) 37 28 35
Wind Direction South South South
Wind Speed (mi/hr) 25-31 mph 33-38 mph 17-22 mph
Expected Snowfall (in) 2-4 7-11 3-5
For 9000 ft to 11000 ft
  Tuesday Tuesday Night Wednesday
Weather Heavy snow and windy. Some thunder is also possible. Wind chill values as low as -7 F. Chance of precipitation 100%. Heavy snow and windy. Wind chill values as low as -12 F. Chance precipitation 100%. Snow showers and windy. Wind chill values as low as -11 F. Some thunder is also possible. Chance of precipitation 100%.
Temperature (°F) 20 14 15
Wind Direction South/Southwest South/Southwest South/Southwest
Wind Speed (mi/hr) 55-65 mph 45-55 mph 40-50 mph
Expected Snowfall (in) 12-18 9-13 3-7


This advisory does not apply to Ski Areas or Highways and is for the Mt. Shasta, Castle Lake and Mt. 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.