Lawinenlagebericht

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
Auf der Karte ansehen

Lawinengefahr

Sun
Hochgebirge
1 · Gering
Waldgrenze
1 · Gering
Unterhalb
1 · Gering
Open full map
Veraltet — dieser Lagebericht ist 5 years ago abgelaufen. Du siehst vergangene Verhältnisse, nicht den aktuellen Bericht.

Kernpunkte

Large avalanches are unlikely, but there is still a slight chance of triggering a large slide on very steep, rocky, wind-affected slopes. As the day warms up, wet snow avalanches will become possible on very steep slopes that face the sun.

Lawinenprobleme

  • Persistent Slabs

    • Hochgebirge
    • Waldgrenze
    • Unterhalb der Waldgrenze
    Wahrscheinlichkeit
    Unlikely
    Größe
    2–3

    Warm and dry weather over the past 2 weeks has caused our persistent layers to go "dormant"—a state where they're unlikely to produce avalanches unless a major loading event occurs. But it's important to remember that these weak layers still exist beneath your feet or sled. The most prominent is the early-season facet layer that's buried 3-4 feet deep (photo above/right).

    As long as the poor snowpack structure exists, there is still a very small chance of triggering a persistent slab avalanche. This leaves you two choices: accept this slight chance, or avoid areas where they are more likely to occur—very steep (approaching 40 degrees), rocky, wind-affected slopes. Terrain like this is most common at upper elevations and especially in the alpine. 

    ADDITIONAL DISCUSSION:High temperatures this weekend are forecast to increase several degrees each day. This will lead to a greater likelihood of wet snow avalanches on steep, sunny slopes. Freezing temps overnight will mean the snowpack will start the day "locked up", but monitor the surface melting as the day heats up. If the slush/mush gets deeper than your boot-tops, or you start breaking through the surface crust, it's time to head for colder or mellower terrain.

    (3/11/2021) Weak layers may be dormant, but they still exist. This snow profile shows soft snow near the surface that steadily hardens until the weak facets carved out near the ground. Photo: J. Preuss

Avalanche Discussion

REMOTE WEATHER STATIONSWith less to talk about with the avalanche conditions, how about we talk about the weather? More specifically—weather stations. They say that "weather is the architect of avalanches", and we rely on a network of remote weather stations to tell us what mother nature is doing up in the mountains when we can't be there in person. Some of us (professional and recreationalists alike) check these with a frequency and passion that borders on obsession. You can view the output of our local weather stations on our map-based viewer as well as by using the trip planner tool.

Broadly speaking, there are two types of weather stations: those that measure snowfall, and those that measure wind. Sites that provide a representative measurement of these parameters are mutually exclusive. Snowfall sites are located in wind-sheltered, mid-elevation sites—typically an open clearing surrounded by trees. Wind sites, by contrast, are located along exposed ridge crests. The Sawtooth Avalanche Center maintains 8 remote stations, and we're lucky to have numerous SNOTEL sites in our area operated by the Natural Resource Conservation Service. Remote stations communicate their data through radio and cellular networks.

Snowfall sites typically measure the following:

  • Air temperature and relative humidity.
  • Occasionally wind, although this isn't representative of ridge-level wind.
  • Snow depth—measured by bouncing sound pulses off the snow and timing how long they take to come back. This form of measurement can be disturbed by snowfall and may be less accurate when the snow surface consists of very low-density snow. 
  • Precipitation—measured when snowfall (or rain) falls and melts in a "bucket" of anti-freeze. The bucket is weighed with a scale. These add expense and complexity to sites, so not every snowfall site has one. The precip gauge usually outputs the inches of melted snow or rain that fell each hour, but SNOTEL sites list the total amount of precip that's fallen since the start of the water year (October 1).
  • Total snow water equivalent (SWE)—at SNOTEL sites, a giant scale ("snow pillow") on the ground measures the weight of the entire snowpack as inches of SWE. 

Wind sites typically measure the following:

  • Air temperature and relative humidity.
  • Wind speed and direction. You would think that placing a station atop a wind-exposed ridge would always give accurate and representative wind values, but that's not the case. Local topography can influence these readings. Upper Titus, for example, tends to be sheltered from NW winds. While the Soldiers are definitely a windy place, Upper Soldier regularly experiences extreme winds when they come from the NW.

Catch up on what happened this past week in Ethan's latest Weekend Update.

Abgedeckte Regionen