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Avalanche Advisory for 2018-01-08 06:59:18

  • EXPIRED ON January 9, 2018 @ 6:59 am
    Published on January 8, 2018 @ 6:59 am
  • Issued by Andrew Kiefer - Mt Shasta Avalanche Center

The avalanche danger will rise to MODERATE above treeline by this afternoon. Strong southerly winds and heavy snowfall are expected over the next 24 hours. Human triggered wind slab avalanches will be possible on steep, recently wind loaded slopes above 8,000ft on Mount Shasta. LOW avalanche danger exists near and below 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

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  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
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New snow and strong southerly winds have the potential to build fresh wind slabs by this afternoon. Wind slabs will likely be found above treeline on NW-N-NE-E aspects. A rise in avalanche danger with the formation of wind slabs will depend on snow accumulation. Watch for signs of wind transported snow like cornices, snowdrifts, and uneven snow surfaces. Avoid recently wind-loaded slopes that are 35 degrees and steeper.

Advisory Discussion

Another wet storm with high freezing levels will begin this morning. Heightened avalanche conditions are expected on steep leeward slopes and terrain features above treeline. Be sure to monitor conditions as they change throughout the day. If the forecast verifies, human-triggered wind slab avalanches will be possible by this afternoon. Snowfall and and gusty winds will also make for challenging travel conditions and poor visibility in the backcountry.

Recent Observations

The weekend finished off with partly cloudy skies and calm conditions. A tour up Avalanche Gulch yesterday confirmed that icefall and rockfall were very active on Casaval Ridge, the Trinity Chutes, and Redbanks.  A large rock peeled off of Casaval ridge and made it all the way down climber’s gully to the 8,500ft level. Icefall was steady throughout the day. No recent avalanches or signs of unstable snow were observed. Firm and chalky snow surfaces made for fast, groomer-like skiing between 10,500-8,000ft. Above, it was icy and variable, and below, ski quality was very poor.

Weather and Current Conditions

Weather Summary

An upper level trough of low-pressure will bring moisture to northern California today. Rain and snow are expected with highs in the mid 30’s to low 40’s. Very strong southerly winds will accompany this storm. Freezing levels will be near 6,000ft today and will rise to 7,000ft overnight and into tomorrow.  The advisory area looks to receive 1.6 inches of water over the next 48 hours. The bulk of precipitation will come today and tonight. At the 7,000ft level, 3-6 inches of wet snow is possible for today, with 1-2 inches expected overnight. Twice that amount of snow is possible for terrain 9,000ft and above by tomorrow morning. Unstable weather will continue through Thursday.

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THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 7.19 inches of water, normal is 16.86 inches, putting us at 43% of normal. For the month of January and 2018, we have received 1.36 inches of water, normal is 1.65 inches, which is 82% of normal. Mount Shasta finished off 2017 with 44.82 inches of water; normal observed value is 43.21, which is 103% of normal.

Always check the weather before you attempt to climb Mount 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.

24 Hour Weather Station Data @ 4:00 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) 44 26 50 42 3 ESE
Sand Flat (6750 ft) 33 25 38 32 11 0 0 0
Ski Bowl (7600 ft) 27 27 37 32 19 0 0 0
Gray Butte (8000 ft) 25 25 36 30 7 25 SW
Castle Lake (5870 ft) 32 31 40 35 0 0 0
Mount Eddy (6509 ft) 31 30 39 34 2 11 SSE 8 0 0
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 Snow before 10am then rain and snow. Chance of precipitation 100%. Rain and snow. Breezy. Chance of precipitation 100%. Rain likely, possibly mixed with snow. Chance of precipitation 70%.
Temperature (°F) 37 32 39
Wind Direction South South/Southeast South/Southeast
Wind Speed (mi/hr) 15-20 mph, gusting 30 mph 15-20 mph, gusting 30 mph 10-15 mph, gusting 20 mph
Expected Snowfall (in) 4-8 1-3 <1
For 9000 ft to 11000 ft
  Monday Monday Night Tuesday
Weather Snow and windy. Chance of precipitation 100%. Snow and windy. Chance of precipitation 100%. Snow likely and windy. Chance of precipitation 70%.
Temperature (°F) 28 25 25
Wind Direction South/Southwest South/Southwest West/Southwest
Wind Speed (mi/hr) 30-40 mph, gusting 60 mph 30-40 mph, gusting 60 mph 25-35 mph, gusting 50 mph
Expected Snowfall (in) 5-9 4-8 1-3

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.