You are here

Avalanche Advisory for 2018-03-07 06:39

  • EXPIRED ON March 8, 2018 @ 6:39 am
    Published on March 7, 2018 @ 6:39 am
  • Issued by Aaron Beverly - Mount Shasta Avalanche Center
  • March 7, 2018 @ 6:39 am

    Advisory Hotline: (530) 926-9613

  • The avalanche danger is LOW at all elevations. Natural and human-triggered avalanches are unlikely. A winter storm will begin to impact the area after 4 p.m. Wind slabs may start to form on NW/N/NE aspects throughout the night.

     

  • Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Avalanche Problem 1: Wind Slab

  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Wind slabs have not been observed over the last few days and are unlikely to be encountered today. However, north aspects retain low density snow that could be transported by strong winds. With 2-4 inches of snow predicted tonight accompanied by S winds over 40 mi/hr, wind slabs may begin to form and grow after 4 p.m. near and above treeline. Look for these on NW/N/NE aspects. Signs of wind slabs include hollow sounding snow, shooting cracks, and wind pillows. When in doubt, stick to windward sides of ridges and avoid slopes over 35 degrees.

Advisory Discussion

Conditions will remain mostly unchanged today with LOW avalanche danger expected at all elevations. Sunny and warm weather yesterday coupled with below freezing temperatures last night may have produced melt freeze crusts on southerly aspects. North aspects should continue to hold dry low density snow. Roller balls and pinwheels may continue on steep southerly slopes, but are not expected to pose a significant avalanche concern. A winter storm will begin to impact the area after 4 p.m. today. If you are spending the night on the mountain, be prepared for strong winds, low wind chills, and the development of wind slabs on NW/N/NE aspects.

Recent Observations

Temperatures over the last 24 hours have ranged from 31-45 °F. Winds have been light, averaging 8 mi/hr.

Sun exposed snow surfaces to at least 8000 ft turned moist yesterday. Roller balls were observed on S/SE steep aspects. North facing slopes retain some dry low density snow that could be transported by strong winds.

A tour to Ash Creek Butte saw a snowpack with continued settlement and increased stability. Snow from the last storm was right side up, up to 100 cm (3 ft) in depth, with F-4F-1F hardness. Column test failures were stubborn to trigger. Small cornices on north aspects could be broken with moderate ski stomping. No obvious signs of avalanches or a wind slab problem were seen. See the most recent observation for details.

 

    Weather and Current Conditions

    Weather Summary

    Today expect increased cloud cover and winds as a low pressure system moves warm wet air into the area. Precipitation will begin after 4 p.m. There is some uncertainty on the timing and amount of snow in this one. Generous forecasts are predicting 2-4 inches of snow tonight and 3-4 tomorrow at mid elevations. However, total precipitable water is predicted to be .79 inches between tonight and Saturday morning. This is likely to translate into 6-12 inches of snow from mid to high elevations. The bulk of this looks to fall Thursday night and Friday morning.

    Snow levels will range from 5000 to 5500 ft.

    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) 35 23 59 41 1 N
    Sand Flat (6750 ft) station down
    Ski Bowl (7600 ft) 35.5 31.5 45.5 38 58.1 0 0 3.5
    Gray Butte (8000 ft) 34.5 31.5 42 36 8 18 ESE
    Castle Lake (5870 ft) 35.5 33 58.5 42 27.5 0 2.5
    Mount Eddy (6509 ft) 36 27.5 46 38.5 2 9 SW 43.5 0 2
    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 Snow likely after 4 p.m. Mostly cloudy. Breezy. Chance of precipitation is 60%. Snow. Low around 31. Windy. Chance of precipitation is 80%. Snow then snow showers. Breezy. Chance of precipitation is 90%.
    Temperature (°F) 44 33 36
    Wind Direction S S S
    Wind Speed (mi/hr) 5-10 mi/hr 15-20 mi/hr 15-20 mi/hr
    Expected Snowfall (in) 0 2-4 3-4
    For 9000 ft to 11000 ft
      Wednesday Wednesday Night Thursday
    Weather Snow likely after 4 p.m. Partly sunny. Wind chill values as low as 13. Windy. Chance of precipitation is 60%. Snow. Wind chill values as low as -4. Windy. Chance of precipitation is 80%. Snow then snow showers. Wind chill values as low as 0. Windy. Chance of precipitation is 90%.
    Temperature (°F) 29 19 22
    Wind Direction S S SW
    Wind Speed (mi/hr) 25-30 mi/hr 45-55 mi/hr 40-50 mi/hr
    Expected Snowfall (in) 0 3-5 4-6

    Season Precipitation for Mount Shasta City

    Period Measured (in) Normal (in) Percent of Normal (%)
    From Oct 1, 2017 (the wet season) 12.20 31.00 39
    Month to Date (since Sep 1, 2018) 1.31 1.50 87
    Year to Date (since Jan 1, 2018) 6.37 15.79 40

    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.