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Avalanche Advisory for 2018-01-24 07:00:08

  • EXPIRED ON January 25, 2018 @ 7:00 am
    Published on January 24, 2018 @ 7:00 am
  • Issued by Andrew Kiefer - Mt Shasta Avalanche Center
  • January 24, 2018 @ 7:00 am

    Advisory Hotline: (530) 926-9613

  • The avalanche danger will rise to CONSIDERABLE above treeline by this afternoon. Fresh wind slabs will form near and above treeline on SE-E-NE-N-NW aspects. Natural avalanches are possible and human triggered avalanche are likely. Heightened avalanche danger is expected through the end of the week as an active weather pattern continues.

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

Avalanche Problem 1: Wind Slab

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Strong southwest winds and new snow will form fresh wind slabs 2-3 feet thick near and above treeline on SE-E-NE-N-NW aspects. Wind slabs will grow in size and distribution throughout day. By the afternoon, natural wind slab avalanches will be possible, and human triggering will be likely. Be especially careful of leeward slopes and cross-loaded terrain features 35 degrees and steeper above treeline. Today, wind slab avalanches will be large enough to bury, injure, or kill a person. Wind slabs can be avoided by sticking to sheltered or wind scoured areas.

Advisory Discussion

Dangerous avalanche conditions will exist in the backcountry by this afternoon. Touchy wind slabs will be widespread near and above treeline. Monitor conditions as they change rapidly throughout the day. Watch for obvious signs of instability like recent avalanches, shooting cracks and whumphs. Look for signs of wind loading like blowing snow, cornices, textured snow surfaces and hollow sounding snow. Check to see how the new snow is bonding to the old snow surface. Expect low visibility and challenging travel conditions. Careful snowpack evaluation, cautious route finding and conservative decision-making are essential today.

Recent Observations

No new snow has fallen as of 7am this morning. Skies remained cloudy yesterday with windy conditions above treeline. A lenticular cloud consumed the upper mountain for most of the day. At 8,000 ft, winds averaged 15-20 mph with 35 mph gusts blowing out of the NW shifting SW overnight. Snow surfaces are variable. Near and below treeline, low-density powder snow can be found on W-N-E aspects, while a thin sun crust exists on steep, open south facing slopes. Above treeline, snow surfaces are wind textured, with many exposed terrain features and N-NW-W aspects scoured down to a slick, icy old snow surface.  

Weather and Current Conditions

Weather Summary

The arrival of a strong frontal system has been slightly delayed, but heavy snowfall will begin mid-morning. The NWS has issued a WINTER STORM WARNING IN EFFECT UNTILL 10PM PST THURSDAY. For today, expect strong southwest winds, high temperatures near 30 degrees, and 1 inch of water by 10pm.  Snow levels should begin at 4,000 ft, dropping to town by this afternoon. Snow accumulations of 10-15 inches are expected at 6,000 ft, with more snow likely at higher elevations. A second front will arrive tomorrow, dropping snow levels further and bringing another round of precipitation. Tonight, we should pick up 2-4 inches of snow, with 3-8 inches forecast for tomorrow. Today will be a potent start to an active weather pattern that will continue through early next week.

Season Precipitation for Mount Shasta City

Period Measured Normal Percent of Normal
From Oct 1, 2017 (the wet season) 9.07 20.13 45
Month to Date (since Feb 1, 2018) 3.24 4.92 66
Year to Date (since Jan 1, 2018) 3.24 4.92 66

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) 37 27 43 35 4 SE
Sand Flat (6750 ft) 28 23 37 29 18 0 0 0
Ski Bowl (7600 ft) 23 23 34 29 35 0 0 0
Grey Butte (8000 ft) 23 21 30 25 15 31 WNW
Castle Lake (5870 ft) 28 26 34 29 3 0 0
Mount Eddy (6509 ft) 27 26 37 28 2 10 S 20 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
  Wednesday Wednesday Night Thursday
Weather Heavy snow and windy. Chance of precipitation 100%. Snow showers. Chance of precipitation 90%. Snow showers. Chance of precipitation 90%.
Temperatures 30 deg. F. 19 deg. F. 23 deg. F.
Wind direction South South/Southwest South
Wind speed 15-25 mph 15-20 mph 15-20 mph
Expected snowfall 15-21 in. 3-5 in. 6-10 in.
For 9000 ft to 11000 ft
  Wednesday Wednesday Night Thursday
Weather Heavy snow and windy. Chance of precipitation 100%. Wind chill values as low as -14. Snow showers. Chance of precipitation 90%. Wind chill values as low as -26. Snow showers and windy. Chance of precipitation 90%. Wind chill values as low as -21.
Temperatures 19 deg. F. 4 deg. F. 17 deg. F.
Wind direction South/Southwest West/Southwest Southwest
Wind speed 40-50 mph, increasing throughout the day 35-45 mph, gusting 50+ mph 35-45 mph, gusting 60+ mph
Expected snowfall 24-30 in. 3-7 in. 6-10 in.

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.