THIS AVALANCHE ADVISORY EXPIRED ON April 17, 2016 @ 6:40 am
Avalanche Advisory published on April 16, 2016 @ 6:40 am
Issued by Brandon Schwartz - Tahoe National Forest

Early this morning, avalanche danger is LOW for all elevations and aspects. Areas of MODERATE avalanche danger will form at all elevations and on all aspects on slopes 35 degrees and steeper as loose wet avalanche problems develop in response to daytime warming.

2. Moderate

?

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

2. Moderate

?

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

2. Moderate

?

Below Treeline
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: Loose Wet
  • Type ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

With clear skies and below freezing air temperatures, a strong snow surface refreeze will have occurred last night. The exception will be in the areas along the Sierra Crest in the northern portion of the forecast area where several inches of storm snow accumulated Wednesday night. In these areas a thin breakable crust will exist on top of recent storm snow that has yet to be affected by melt-freeze. This remnant storm snow sits on top of hard melt-freeze crust. In areas that received little to no new snow this past week or were wind scoured yesterday, expect hard melt-freeze crust at the snow surface

As daytime warming occurs, snow surface melt is expected to today. Melt will occur mainly on E-SE-S-SW-W aspects with some degree of melt occurring on NW-N-NE aspects as well. Areas with remnant storm snow on the surface and direct sun exposure will be the most prone to loose wet avalanches today.  Areas with melting crust will become unstable once the surface crust looses supportability.

In areas with recent new snow, roller balls, pinwheels, and test slope failures will be the indicator that unstable wet snow is developing. In areas without recent storm snow, body weight boot penetration into surface wet snow will be the indicator. Boot penetration of 8 to 10 inches or more is problematic. When signs of wet snow instability are present, exit avalanche terrain by moving onto slopes less than 30 degrees in slope angle without steeper terrain above.

recent observations

Observations made yesterday on Castle Peak (Donner Summit area) revealed unstable wet snow in sun affected areas and blowing snow along the ridgetops. At noon, ski cuts on steep E aspect micro terrain features within a macro scale S aspect produced small loose wet avalanches. These avalanches involved all of the 4 inches of recent storm snow and ran on the hard melt-freeze crust below it. Areas of blowing snow were visible all along the Sierra Crest in the Donner Summit area, but new wind slab formation was minimal.

Weather and CURRENT CONDITIONS
weather summary

High pressure continues to build over the forecast area. Ridgetop winds will remain out of the E to NE today but decrease to moderate in speed. Winds are forecast to become light on Sunday. Sunny skies and clear nights are expected through the weekend. A warming trend is ongoing with maximum daytime air temperatures warming to around average today and above average on Sunday.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 28 to 32 deg. F.
Max. temperature in the last 24 hours: 36 to 38 deg. F.
Average wind direction during the last 24 hours: NE
Average wind speed during the last 24 hours: Sensors offline, est at 40 mph
Maximum wind gust in the last 24 hours: Sensors offline, est at 80 mph
New snowfall in the last 24 hours: 0 inches
Total snow depth: 60 to 106 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Saturday Saturday Night Sunday
Weather: Sunny skies. Clear skies. Sunny skies.
Temperatures: 45 to 52 deg. F. 30 to 36 deg. F. 52 to 59 deg. F.
Wind Direction: E E E
Wind Speed: 15 to 20 mph with gusts to 30 mph. 10 to 15 mph. Gusts to 25 mph after midnight. 10 to 15 mph in the morning, becoming light.
Expected snowfall: 0 in. 0 in. 0 in.
For 8000 ft. to 9000 ft.
Saturday Saturday Night Sunday
Weather: Sunny skies. Clear skies. Sunny skies.
Temperatures: 41 to 48 deg. F. 26 to 33 deg. F. 47 to 54 deg. F.
Wind Direction: E E E
Wind Speed: 20 to 25 mph with gusts to 40 mph. 15 to 20 mph with gusts to 30 mph. 10 to 15 mph.
Expected snowfall: 0 in. 0 in. 0 in.
Disclaimer

This avalanche advisory is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This advisory covers the Central Sierra Nevada Mountains between Yuba Pass on the north and Ebbetts Pass on the south. Click here for a map of the forecast area. This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.

For a recorded version of the Avalanche Advisory call (530) 587-3558 x258