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Avalanche Advisory for 2013-03-02 06:59:25

  • EXPIRED ON March 3, 2013 @ 6:59 am
    Published on March 2, 2013 @ 6:59 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

For today, the overall avalanche danger remains LOW for all aspects and elevations. We received no new snow over this past week with predominantly moderate northwest winds. Instabilities are unlikely and will be limited to areas of wind loading near ridgetops, bowls, rock outcrops, chutes and gullies on all aspects and on slopes steeper than 35 degrees. Most other areas have been scoured down to the old, firm snow surface and/or entered a melt/freeze cycle. Normal caution advised.

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

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

  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Very Likely
  • Size ?
    Very Large

In general, a lot of variability exists out there concerning the depth, location and sensitivity to triggering of the wind slabs. While finding and triggering a wind slab will be very unlikely today, it will not be impossible. Isolated pockets of wind loaded snow may be found and potentially triggered with the weight of multiple skiers and/or snowmobile.  Normal caution advised.

Recent Observations

No new recent avalanches observed or reported since last Sunday and observations over the week were limited, 2-24-13.

2-23-13  North side of Mt. Shasta, 4-8 inches new snow, wind affected. Traveled only to the trailhead, not in avalanche terrain. Several feet of snow at the trailhead and no recent tracks. Snowmobiles necessary for approx. 5 miles of road to access the trailhead. Very cold, poor visibility, snowing lightly at the time.

2-22-13  Mt Eddy area, NW aspect, 35 degree slope... ECTP 2 / Q1 - Failures on same layers as seen at Castle Lake...small, faceted snow crystals above and below buried crust layer, 30-40 cm deep in wind loaded area. Weakest layer has been below this crust layer. No recent nature/human triggered avys observed.

2-21-13 - Castle Lake area, NW aspect, 30 degree slope on Middle Peak... CT-6 / ECTP - 4 - Q1/2 -   Failures near buried crust on layer of facets, above old snow, about 30-40 cm down from surface, wind deposited snow, full propagation hard slab. No recent nature/human triggered avys observed.

2-20/2-21 - Numerous reports of "whoomfing" and shooting cracks near and above treeline on Mt. Shasta: Giddy Giddy gulch, Anaconda, The Promise Land areas.

2-20-13 - Avalanche Gulch, Spring Hill area, small wind slab avalanche (R1-D2), unknown trigger

Below: ECTP-4 / Q2 at Castle Lake on 2-21. Received same results (ECT-2) in Mt. Eddy area, wind loaded NW aspect.


    Weather and Current Conditions

    Weather Summary

    We have low pressure moving through the area which will bring some precipitation this evening. It may start as rain down low but should produce a couple inches of snow overnight. Up to .16 inches of water is expected by tommorow morning with the heaviest precip during the late evening. We hope to see more snow than rain, but warm temps will keep freezing levels near Bunny Flat (6950') or higher until Sunday. It looks like dry weather for Sunday and Monday with a slightly larger storm coming in Tuesday and Wednesday.

    WEATHER STATIONS - (last 24 hours):
    In Mt. Shasta City at 0500, we have partly cloudy skies and a current temperature of 35 F.
    On Mt. Shasta:  In the Old Ski Bowl (7,600') on the south side of Mt. Shasta, we have a current temperature of 39 F. Snow on the ground totals 95"  inches with no new snow and little settlement. Temperatures have ranged from 35 F to 47F.  At Grey Butte (8,000') on the south side of Mt. Shasta winds averaged 5 mph from various directions with a max gust of 21 mph from the NW. The current temperature is 37 F and temps have ranged 36 F to 45 F.
    Castle/Mt. Eddy:   Castle Lake - Castle Lake is hosting a current temp of 42 F. In the last 24 hours temperatures have ranged from 36 F to 55 F. Snow depth measures 44" inches with no new snow and little settlement.  On Mt Eddy, we have 62" inches of snow on the ground with no new snow and little settlement. The current temperature reads 39 F with temps ranging from 29 F to 50 F. Winds have been SW, averaging 5 mph from various directions and gusting to 8 mph from the ESE.

    THIS SEASON:  September and October were warm and dry with September recording exactly zero precipitation. November remained warmer than normal with precipitation almost double normal values, 9.16" vs. 5.08". A local weather COOP observed the 2nd wettest November on record. December started out wet and warm, but temperatures cooled and brought snow to very low elevations. Since our avalanche cycle near Christmas, we've had a few small storms that brought some amounts of snow to the area, but did not produced any notable avalanches. January was below normal for precipitation with a long period of high pressure and sun that kept skiing conditions somewhat meager. We've had a few storms in the past few weeks that have brought a pittance of wintery weather, but nothing to write home about!  The area has been under siege by high pressure overall and giving us blue bird days for the most part. A disturbance this next week could bring up to an inch of water to the area with higher snow levels. California and the Sierra Nevada have recorded the driest January and February on record. We currently have 6-10 feet of snow above 6,500 ft. Since September 1st, Mt Shasta sits at 74% of normal, 22.55" recorded; normal 30.43". For 2013, we sit at 12% of normal with 1.85" recorded and 14.55" normal.

    CURRENT CONDITIONS at Bunny Flat (6950 ft)
    0600 temperature: 37
    Max. temperature in the last 24 hours: 49
    Average wind direction during the last 24 hours: variable
    Average wind speed during the last 24 hours: 0-5 mi/hr
    Maximum wind gust in the last 24 hours: NW-21 mi/hr
    New snowfall in the last 24 hours: 0 inches
    Total snow depth: 58-95 inches

    Two Day Mountain Weather Forecast

    Produced in partnership with the Medford NWS

    For 7000 ft to 9000 ft
    (4 a.m. to 10 p.m.)
    Saturday Night
    (10 p.m. to 4 a.m.)
    (4 a.m. to 10 p.m.)
    Weather Mostly cloudy Rain and snow Cloudy in the morning and clearing in the afternoon.
    Temperature (°F) 50 28 42
    Wind (mi/hr) SW 5-10 mph NW 10-15 mph N 10-15 mph
    Precipitation SWE / Snowfall (in) / trace / 1-2 / trace
    For 9000 ft to 11000 ft
      Saturday Saturday Night Sunday
    Weather Increasing clouds with snow in the afternoon Snow Clouds clearing slightly throughout the day
    Temperature (°F) 33 19 30
    Wind (mi/hr) SW 20-30 mph with gusts higher SW 1 SW 25-35 mph with gusts higher
    Precipitation SWE / Snowfall (in) / 1 / 1-2 / .5


    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.