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Avalanche Advisory for 2018-04-10 06:33

  • EXPIRED ON April 11, 2018 @ 6:33 am
    Published on April 10, 2018 @ 6:33 am
  • Issued by Aaron Beverly - Mount Shasta Avalanche Center

A weak frontal system may bring a few inches of snow at elevations above 8000 ft leading to the formation of small wind slabs. Avalanche danger will rise to MODERATE late this afternoon above treeline. Avalanche danger is LOW at all other elevations. Be prepared for smooth icy snow surfaces and gale force winds.

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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Small wind slabs may begin to form above treeline this afternoon on west, north, and east aspects. Smooth firm snow surfaces exist that will provide ideal bed surfaces for avalanches. These will unlikely be large enough to bury a person, but could be touchy to trigger and may cause a slide for life situation down steep icy slopes.

Avoid wind slabs by traveling in windward areas where snow surfaces have been eroded. Avoid slopes greater than 35 degrees where wind loading has occurred. Evaluate conditions as you travel in safe terrain by looking for signs of the wind slab problem:

  • Smooth rounded wind pillows
  • Hollow sounding snow
  • Harder snow atop softer snow
  • Shooting cracks

Advisory Discussion

Smooth snow surfaces exist on all aspects. A cooling weather pattern means these surfaces will stay icy during the day. An ice axe and crampons are mandatory for climbing up steep terrain. Self-arrest will be difficult in these conditions.

Active icefall was observed yesterday and many grapefruit sized ice balls were seen in gullies below Helen Lake. Colder weather will keep this at bay, but be prepared for it nonetheless. Wear a helmet!

Winds could reach gale force velocities. Be ready to receive a pummeling if venturing above treeline today.

Recent Observations

No new snow was received last night. The temperature reached a high of 53 °F at the Old Ski Bowl weather station.

Yesterday, Avalanche Gulch hosted near perfect corn skiing conditions on all aspects by 2:30 p.m. Snow surfaces were smooth. Thin layers of soft corn snow sat atop firm consolidated snow. Small roller balls could be ski-triggered on aspects exposed to direct sun, but there were no natural signs of wet loose activity. Westerly aspects were extremely icy in the morning.  A hiker/climber was observed taking a hair-raising slide off of Green Butte Ridge. Person was uninjured. Grapefruit sized balls of ice were seen in gullies below Helen Lake and ice fall was active out of Red Banks and the Trinity Chutes.

Weather and Current Conditions

Weather Summary

A weak warm front moves in from the coast today. Precipitation at near and below treeline elevations will see this in the form of rain and wet snow. Snow levels look to be 8000-9000 ft. Above treeline, 2-3 inches of snow is possible. South winds could reach speeds above 50 mi/hr.

A stronger front moves in tomorrow bringing colder temperatures and the possibility of several inches of snow above 5000 ft.

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) 52 31 73 57.5 2 N
Sand Flat (6750 ft) station down
Ski Bowl (7600 ft) 37.5 37.5 52.5 44.5 73.5 0 0 1.5
Gray Butte (8000 ft) 36.5 36.5 52 44.5 8 31 ESE
Castle Lake (5870 ft) station down
Mount Eddy (6509 ft) 41 34.5 57 47 2 11 SSW 37.5 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
  Tuesday Tuesday Night Wednesday
Weather Rain. Windy. Chance of precipitation is 80%. A chance of rain and snow showers before 11 p.m., then a slight chance of snow showers. Mostly cloudy. Chance of precipitation is 30%. Snow. Breezy. Chance of precipitation is 100%.
Temperature (°F) 41 30 34
Wind Direction S S S
Wind Speed (mi/hr) 15-20 10-15 15-20
Expected Snowfall (in) 0 <0.5 2-4
For 9000 ft to 11000 ft
  Tuesday Tuesday Night Wednesday
Weather Snow. Windy. Chance of precipitation is 80%. A 30 percent chance of snow showers, mainly before 11 p.m. Mostly cloudy. Wind chill values as low as -7. Windy. Snow. Wind chill values as low as -11. Windy. Chance of precipitation is 90%.
Temperature (°F) 30 21 22
Wind Direction SW SW SW
Wind Speed (mi/hr) 50-60 30-35 40-45
Expected Snowfall (in) 2-3 <0.5 2-4

Season Precipitation for Mount Shasta City

Period Measured (in) Normal (in) Percent of Normal (%)
From Oct 1, 2017 (the wet season) 17.17 36.47 47
Month to Date (since Oct 1, 2018) 1.22 1.01 121
Year to Date (since Jan 1, 2018) 11.34 21.26 53

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.