You are here

Avalanche Advisory for 2014-03-08 06:58:49

  • EXPIRED ON March 9, 2014 @ 7:58 am
    Published on March 8, 2014 @ 6:58 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

Today, overall MODERATE avalanche danger will form on sun affected slopes, E-SE-S-SW-W aspects, 35 degrees and steeper. Above freezing temperatures last night and warm daytime highs today will cater towards loose wet avalanches on said aspects. Loose wet avalanche instabilities will increase as the day warms.

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Avalanche Problem 1: Wet Slab

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

Temperatures have been above freezing since 1400 yesterday. Even warmer temperatures are expected today. This will increase the chance for wet snow avalanches. Slopes greater than 35 degrees on E, SE, S, SW and W facing should be most suspect during the warmest portions of the day. Wet snow instabilities will likely be in the form of roller balls and small wet snow sluffs. Some could entrain enough snow however to cause a problem for backcountry riders.


 

Avalanche Problem 2: Wind Slab

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

Wind slabs on Mt Shasta have shown good stability over the past two days with no natural or human triggered activity. Use normal caution near ridgetops and bowls concerning hard wind slabs on the upper mountain, above 9,000 feet and all aspects.

Avalanche Problem 3: Cornice

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

Always be cautious of corniced ridgelines when new snow and winds are present. Stay back on terra firma as cornices can break back much further than expected.

Recent Observations

Overall good snow stability was found yesterday during a tour of Casaval Ridge and Avalanche Gulch. Smooth snow above treeline and good skiing conditions have brought many folks up onto the mountain. A handful of skiers descended from Redbanks yesterday. Snow conditions range from firm, frozen crust, wind packed powder, to smooth and creamy! Lower elevation crusts were sometimes breakable by a skier and sometimes not. Weak layers in the snowpack have varied from location to location. Most common has been failures at or near buried crust layers. However, a pit dug on an east facing aspect of Casaval Ridge yesterday yielded a 2-5 cm weak layer of graupel, about 30 - 40 cm deep. Stability tests showed moderate stability within this weak layer and full slope propagation not likely. (CT11-Q2/ECTN22-Q2)

--------------------------------------------------------------------------------------------

Commentary From 3-7-14

Of note since last week, at least two avalanches occured in Avalanche Gulch. Both were assumed to be naturally triggered. The larger slide started near The Heart and ran down below Lake Helen, splitting the morain. (D2/3, R2.5)

Photo courtesy of Chris Carr, Shasta Mountain Guides. This photo shows the toe/debris of the larger slide that occured sometime on March 2nd or 3rd. Green Butte and Sargents Ridgelines are in background.

The second, smaller slide occured off of Casaval Ridge and slid down into climbers gully in Avalanche Gulch. The slides were thought to be wind and storm slab avalanches, although the larger of the slides appeared to look like a wet slide due to it's gouging of the snowpack. However, due to the high elevation of the start zone, a wet slide is doubted and it was likely just heavy debris.

Photo courtesy of Chris Carr, Shasta Mountain Guides. Wind Slab avalanche off of Casaval Ridge expected to have occured March 3 or 4th. Lake Helen is up and to the right, out of the photo.

Overall, a thick (2-3 inch) rain crust dominates our backcountry snowpack. I was able to wiggle up to 8,500 feet yesterday in the Old Ski Bowl before visibility became nil. Of course when I returned to Bunny Flat the clouds lifted. Below the crust, very moist. greasy snow exists. While this could cause concern for wet slides, below freezing temperatures last night and said crust will keep this problem unlikely today. The primary concern will be for pockets of wind slab avalanches that have formed on the upper mountain near ridgetops and bowls. These will be found above the rain/snow line, greater than 9,000 feet.

Stability test at test pit yesterday at 8,100 feet, southeast aspect, 31 degrees resulted in an ECTN-Q3 and CT11-Q3@120cm from ground.

Photo courtesy of Chris Carr, Shasta Mountain Guides. Powder riding in Avalanche Gulch from this past week.

2014-03-06: Test pit profile, 8,100 feet, SE, 31 degrees, ECTN-Q3 and CT11@120cm

---------------------------------------------------------------------------------------------------------------------------------------------------------------

While Northgate, Brewer Ck and Clear Ck trailheads are officially closed, the bathrooms are still open with packout bags inside, and one can still access the Mt Shasta Wilderness. However, your summit pass and wilderness permits must be purchased at McCloud or Mt Shasta Ranger Stations. NO DOGS are allowed in the Mt Shasta Wilderness OR Sierra Club Property. Thanks!

---------------------------------------------------------------------------------------------------------------------------------------------------------------

Terrain:  Remember most of the terrain that we like to play on is greater than 30 degrees.  Avalanches are possible on anything steeper than 30 degrees.  Avoid cornices, rock bands, terrain traps and runout zones of avalanche paths.

Weather:  Most of our areas avalanche danger will occur 24-48 hours after a storm. We still can see persistent weak layers from time to time and we always will be sure to let you know about that!  Heed the basic signs: Wind (significant snow transport and depositions), Temperature (rain/snow/rain/snow, which in turn weakens the snowpack), and Precipitation (Snow or rain add weight and stress to the current snowpack).

SnowpackIf snow accumulates, give the snowpack a chance to adjust to the new snow load before you play on or near steep slopes (greater than 30 degrees).  Most direct action avalanches occur within 24-48 hours of recent snowfall.  Watch for obvious signs of snowpack instability such as recent natural avalanche activity, collapsing of the snowpack (often associated with a “whumphing” sound), and shooting cracks. If you see these signs of instability, limit your recreation to lower angle slopes.

Human Factor: Don’t forget to carry and know how to use avalanche rescue gear. You should NOT be skiing or climbing potential avalanche slopes without having beacons, shovels, and probes.  Only one person in a group should be exposed to potential avalanche danger at a time.  Remember, climbing, skiing, and riding down the edge of slopes is safer than being in the center.  Just because another person is on a slope doesn’t mean that it is safe.  Be an individual!  Make your own decisions.  Heed the signs of instability: rapid warming, “whumphing” noises, shooting cracks, snowing an inch an hour or more, rain, roller balls, wind loading, recent avalanche activity.

 


 

    Weather and Current Conditions

    Weather Summary

    In Mt Shasta City this morning at 0500, we have clear skies with a current temperature of 33 F.

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

    Old Ski Bowl - 7,600 feet. The Old Ski Bowl weather station has received no new snow in the last 24 hours. The current temperature is 36F with a low of 22F and a high of 37F. Total snow depth is 59 inches with 1 inch of settlement since yesterday.

    Gray Butte - 8,000 feet - The current temperature is 38F. Temps have ranged from a low of 23F to a high 38F.  Winds have averaged 12 mph primarily from the E. Gusts hit 35 mph from the E at 700 to 800 yesterday morning..

    Castle Lake and Mt Eddy (West side of I-5)... 

    Castle Lake - 5,600 feet, the current temperature is 40F with a low of 27F and a high of 47F. Castle Lake has received no new snow and has a current snowpack of 5 inches with 1 inch settlement since yesterday.

    Mt Eddy - 6,500 feet, the current temperature is 36F with a low of 22F and a high of 41F. Mt Eddy has received no new snow and hosts a current snow depth of 22 inches. Winds have averaged 2 mph with gusts to 8 mph, southerly in nature.

    THIS SEASON: Since September 1st , we have received 10.75 inches of water, normal is 31.90 inches, putting us at 33% of normal. For the year of 2014, Mt Shasta has received 7.93 inches of water with normal being 16.02 inches which puts us at 49% of normal. And lastly, for March we sit at 109% of normal, receiving 1.89 inches of water, normal is 1.73 inches.

    WEATHER SYNOPSIS:

    An even warmer day today will kick off the weekend with high temperatures in town creeping to near 70 F degrees! A long stream of moisture extends out this morning to the Hawaiian islands and we should see increasing clouds as this system moves on shore later today.  Precipitation will begin Saturday night and should be steady through Sunday. The heaviest precip is expected to be in the late afternoon on Sunday. While the moisture is welcomed, the temperatures and snow levels look quite high. Snow levels will start near 9,000 to 10,000 feet. We will see a gradual cooling as the storm progresses, however by the time the snow level drops to 6,000 feet, most of the moisture will have fallen. So, this means rain on snow for a good portion of the snowpack on the mountain. 1.34 inches of water is expected by the end of the weekend. Winds will be light this morning and picking up, West/Southwest and blowing 30-40 mph with gusts higher by tomorrow.

    CURRENT CONDITIONS at Bunny Flat (6950 ft)
    0600 temperature: 36
    Max. temperature in the last 24 hours: 37
    Average wind direction during the last 24 hours: E-WNW
    Average wind speed during the last 24 hours: 12 mi/hr
    Maximum wind gust in the last 24 hours: 35 mi/hr
    New snowfall in the last 24 hours: 0 inches
    Total snow depth: 59 inches

    Two Day Mountain Weather Forecast

    Produced in partnership with the Medford NWS

    For 7000 ft to 9000 ft
      Saturday
    (4 a.m. to 10 p.m.)
    Saturday Night
    (10 p.m. to 4 a.m.)
    Sunday
    (4 a.m. to 10 p.m.)
    Weather Mostly clear, increasing clouds in the late afternoon, chance of rain in evening Rain, mostly after 10pm Rain
    Temperature (°F) 47 36 41
    Wind (mi/hr) South / Southeast 5-10 mph East / Northeast 10-15 mph East 5-10mph
    Precipitation SWE / Snowfall (in) / 0 / .25-.5 water / .75-1 water
    For 9000 ft to 11000 ft
      Saturday Saturday Night Sunday
    Weather Sunny and clear this morning with increasing clouds this afternoon/evening, slight chance of rain/snow Snow, mostly after 10pm Snow
    Temperature (°F) 39 30 33
    Wind (mi/hr) Southwest 30-40 mph Southwest 0-.5 Southwest 25-35 mph
    Precipitation SWE / Snowfall (in) / 0-.5 / 1-3 / 3-7

    Disclaimer

    This advisory does not apply to Ski Areas or Highways and is for the Mt. Shasta, Castle Lake and Mt. Eddy back country. Use this information for guidance only. You may find different conditions in the back country and should travel accordingly. This advisory expires on midnight of the date it was posted unless otherwise noted.