Avalanche forecast

Central Sierra Nevada

Sierra Avalanche Center
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Avalanche danger

Alpine
2 · Moderate
Treeline
2 · Moderate
Below
2 · Moderate
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Highlights

Very early this morning while the snow surface remains frozen, LOW avalanche danger exists for all elevations and aspects. Areas of MODERATE avalanche danger will form quickly in response to snow surface melt as the morning progresses. Starting during the mid to late morning hours, human triggered loose wet avalanche activity will become possible on all aspects at all elevations on slopes 35 degrees and steeper.

Avalanche problems

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2

    Air temperatures were in the mid 30s to low 40s for most locations again last night. In open areas, a decent but superficial snow surface refreeze is expected to have occurred last night fueled entirely by radiational cooling. This superficial snow surface refreeze is expected to melt rapidly this morning, exposing the deeper wet snow below and allowing for the possibility of loose wet avalanches today. In treed areas, overnight snow surface refreeze may have been poor. The high sun angle this time of year will allow for snow surface melt to affect all aspects. The most rapid melt will occur on E-SE-S-SW-W aspects. NW-N-NE aspects that are shaded in February will experience more sun exposure, little shade, and snow surface melt today, even at the upper elevations.

    Timing of travel in and below avalanche terrain is critical today for avalanche avoidance. Late starts (mid morning and beyond) are not advised for finding the ideal balance of quality recreation and minimum hazard in avalanche terrain. Late starts lead to lower quality recreation and greater avalanche hazard. Pay attention to how the snow feels under equipment and the degree of supportability. When the snow surface feels like it is loosing supportability and equipment is penetrating deeper into wet snow, conditions are becoming ripe for a loose wet avalanche to occur. Human triggered roller balls, pinwheels, and deep penetration into wet snow are the instability clues that exist prior to avalanche occurrence. When signs of wet snow instability are present, stop ascending and move to slopes less than 35 degrees in slope angle without steeper terrain above.

Avalanche Discussion

Yesterday, observations made on Mt. Tallac (Desolation Wilderness area) and recieved from the Sierra Crest between Mt. Anderson and Mt. Lincoln (Donner Summit area) revealed a poor to decent snow surface refreeze had occured the night before. By the mid morning hours, the snow surface on E-SE aspects had become unsupportable in some areas at low and mid elevations. By noon, signs of loose wet instablity had spread to other aspects, including northerly aspects at 9,000'. Widespread areas of unsupportable wet snow were noted at noon below 7,000'. More specific info below.

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