THIS AVALANCHE ADVISORY EXPIRED ON April 7, 2017 @ 6:42 am
Avalanche Advisory published on April 6, 2017 @ 6:42 am
Issued by Aaron Beverly - Mount Shasta Avalanche Center
bottom line

Avalanche danger will increase throughout the day to CONSIDERABLE near and above treeline as new snow combines with moderate to strong winds to form wind slabs. Evaluate changing conditions throughout the day. Avoid slopes greater than 30 degrees where wind loading is occurring. Avalanche danger below treeline is MODERATE.

How to read the advisory


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

3. Considerable

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Above Treeline

3. Considerable

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Near Treeline

2. Moderate

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Below Treeline

Avalanche danger will increase throughout the day to CONSIDERABLE near and above treeline as new snow combines with moderate to strong winds to form wind slabs. Evaluate changing conditions throughout the day. Avoid slopes greater than 30 degrees where wind loading is occurring. Avalanche danger below treeline is MODERATE.

  • Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.
Avalanche Problem 1: Wind Slab
  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

With 8 inches of new snow overnight, and at 2-4 expected today, combined with moderate to strong south and southwest winds, wind slabs could become an issue as the day progresses. The old snow interface will provide a firm bed surface on which a wind slab could slide. Look for these on the lee slopes, near and above treeline. Slabs may exist on northwest, north, northeast, and east slopes near treeline. Above treeline, look for slabs on all aspects. Isolated slabs may exist below treeline near terrain exposed to the wind.

Mountain winds can be variable, so always pay attention to where the wind is blowing snow. Avoid wind loaded slopes greater than 30 degrees.

advisory discussion

Looks like today could be a good ski day afterall.

Both Sand Flat and the Old Ski Bowl are reporting 7-8 inches of new snow since 11 PM last night. These amounts are significantly more than what was predicted. Moderate to strong winds are likely to start transporting this snow near and above treeline increasing wind slab hazards through out the day. Wind slabs may grow to 8-12 inches in thickness or more. Monitor conditions as you travel. Look for shooting cracks in the snow as an indicator of this problem.

Late tonight more snow is on the way which will add more weight to the snowpack and will continue to increase avalanche hazard.

recent observations

If our weather stations are to be believed, we have received much more snow than predicted.

The Old Ski Bowl (7600') is reporting 8 inches of new snow since 11 PM last night. Winds have been southwest, south southwest, and south ranging from 11 - 13 mph. Temperatures have been at or below the freezing level and decreasing from the start of this precipitation event.

Sand Flat (6750') is reporting 7 inches of new snow. Castle Lake 6 inches.

CURRENT CONDITIONS Weather observations from Bunny Flat
0600 temperature: 30 deg. F.
Max. temperature in the last 24 hours: 46 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 11 mph
Maximum wind gust in the last 24 hours: 35 mph
New snowfall in the last 24 hours: 7 inches
Total snow depth: 107 inches
weather

A winter storm watch will be in effect from late tonight through friday morning.

Snow levels are expected to be 4500 feet today and 3900 feet tomorrow. The effects of a weak cold front could produce up 4 inches of snow today. Late tonight a warm front will pass through bringing with it significant precipitation and winds. Expect strong to gale force southerly winds near and above treeline. This system could drop over 3 inches of water by Saturday and over two feet of snow.

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In Mt Shasta City at 0500, we have a current temperature of 34 F

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

Sand Flat - 6,750 ft. The current temperature is 30 degrees F. Temperatures have ranged from 30 F to 46 F. Snow on the ground totals 107 inches with 7 inches of snow and 1 inch of settlement.

Old Ski Bowl - 7,600ft. The current temperature is 25 degrees F. Temperatures have ranged from 34 F to 48 F. Snow on the ground totals 182 inches with 8 inches of new snow and 1.5 inches of settlement. 

Grey Butte - 8,000 feet. The current temperature is 26 degrees F. Temperatures have ranged from 26 F to 43 F. Winds have averaged 11 mph with gusts to 35 mph, blowing south, south southwest, and southwest.

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

Castle Lake - 5,800 feet. The current temperature is 31 degrees F. Temperatures have ranged from 31 F to 49 F. Snow on the ground totals 93 inches with about 6 inches of new and 2 inches of settlement.

Mt Eddy - 6,500 feet, the current temperature 30 degrees F. Temperatures have ranged from 30 F to 43 F. Snow on the ground measures 83 inches with a trace of new snow and about 2 inches of settlement. Winds have been variable averaging 2 mph with gusts up to 18 mph.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 49.60 inches of water, normal is 36.04 inches, putting us at 138% of normal. For the month of April, we have received 0.14 inches of water, normal is .58 inches, which is 24% of normal. And finally for the year of 2017, we received 28.44 inches of water, normal is 20.83 inches, putting us at 137% 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.

 

Two-Day Mountain Weather Forecast Produced in partnership with the Medford NWS
For 7000 ft. to 9000 ft.
  Thursday Thursday Night Friday
Weather: Snow likely before 11am, then a chance of snow showers after 11am. Cloudy. Windy. Chance of precipitation is 70%. Snow. The snow could be heavy at times. Low around 28. Windy. Chance of precipitation is 100%. Snow before 11am, then snow showers after 11am. Windy. Chance of precipitation is 100%.
Temperatures: 39 deg. F. 28 deg. F. 34 deg. F.
Wind direction: South South South
Wind speed: 15-25 mph, with gusts up to 60 20-30 mph 20-30
Expected snowfall: 2-4 in. 9-18 in. 3-6 in.
For 9000 ft. to 11000 ft.
  Thursday Thursday Night Friday
Weather: Snow likely before 11am, then a chance of snow showers after 11am. Cloudy. Windy. Chance of precipitation is 70%. Snow. The snow could be heavy at times. Windy. Chance of precipitation is 100%. Snow before 11am, then snow showers after 11am. The snow could be heavy at times. Windy. Chance of precipitation is 100%.
Temperatures: 23 deg. F. 12 deg. F. 16 deg. F.
Wind direction: Southwest South Southwest
Wind speed: 54 mph 62 mph 55 mph
Expected snowfall: 2-4 in. 9-18 in. 3-6 in.
Disclaimer
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.