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.


This Avalanche Advisory was published on March 27, 2013:

March 27, 2013 at 6:35 am

Avalanche danger is LOW for all elevations and aspects. Normal caution is advised.

Forecast Discussion:

A mix of cloud cover and occasional very light precipitation is expected again today and tomorrow across the forecast area. Snow level is forecast at around 7,000' to 7.500' for both days. Shower activity is once again expected to peak during the afternoon hours as daytime warming drives atmospheric instability. Any new snow accumulations are not expected to exceed trace accumulations. Ridgetop winds out of the southwest decreased from strong to moderate in speed over the past 24 hours. Moderate speed southwest winds are forecast to continue today and tomorrow. This morning, remote sensors above 8,000' are reporting air temperatures in the mid 20s to low 30s. Maximum daytime air temperatures for areas above 7,000' are expected to reach the low 30s to upper 40s, very similar to yesterday.

Recent Observations:

Observations made yesterday on Tamarack Peak (Mount Rose area) revealed well established melt-freeze conditions on E-SE-S-SW-W aspects. Northerly aspects held pockets of cold unconsolidated snow around 4-5 inches deep left over from the last storm cycle. Evidence of a decent overnight refreeze of the surface snow was evident in the areas traveled on E-SE-S aspects between 8,600' and 9,500'. At noon, these slopes held 0.5 to 1.5 inches of wet surface snow over supportable melt-freeze crust.

Snowpit tests were performed that targeted an old near crust facet layer that exists within the top foot of the snowpack on northerly aspects in this area. This layer showed characteristics for likely propagation back on March 22nd. Test results from yesterday indicated that propagation along this layer in now very unlikely and that significant stabilization had occurred over the previous 4 days (pit profile, more info).

Avalanche Problem #1: Loose Wet Avalanches

Patchy cloud cover last night is expected to have created some variance in the strength of overnight snow surface refreeze. In areas with less cloud cover, a strong overnight refreeze is expected to have occurred. In areas with more cloud cover, a weaker marginal overnight refreeze may have occurred. Mid and high level cloud cover again today will serve to slow the rate of snow surface melt. While small amounts of wet surface snow are likely to form today on E-SE-S-SW-W aspects, natural and human triggered loose wet snow avalanches are unlikely. Very isolated areas of locally greater avalanche danger could form in areas where a marginal snow surface refreeze occurred last night and prolonged sun breaks occur today.


The bottom line:

Avalanche danger is LOW for all elevations and aspects. Normal caution is advised.


Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

Weather Observations from along the Sierra Crest between 8200 ft and 8800 ft:

0600 temperature: 27 to 33 deg. F.
Max. temperature in the last 24 hours: 32 to 39 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 26 mph
Maximum wind gust in the last 24 hours: 42 mph
New snowfall in the last 24 hours: 0 to trace inches
Total snow depth: 49 to 85 inches

Two-Day Mountain Weather Forecast - Produced in partnership with the Reno NWS

For 7000-8000 ft:
  Wednesday: Wednesday Night: Thursday:
Weather: Mostly cloudy skies with isolated showers. Mostly cloudy skies with isolated showers. Mostly cloudy skies with a chance of showers.
Temperatures: 41 to 48 deg. F. 25 to 30 deg. F. 40 to 46 deg. F.
Wind direction: SW SW SW
Wind speed: 10 to 15 mph with gusts to 25 mph. 15 to 20 mph with gusts to 30 mph. 10 to 15 mph with gusts to 25 mph.
Expected snowfall: 0 to trace in. 0 to trace in. 0 to trace in.

For 8000-9000 ft:
  Wednesday: Wednesday Night: Thursday:
Weather: Mostly cloudy skies with isolated snow showers. Mostly cloudy skies with isolated snow showers. Mostly cloudy skies with a chance of snow showers.
Temperatures: 32 to 42 deg. F. 22 to 29 deg. F. 32 to 41 deg. F.
Wind direction: SW SW SW
Wind speed: 15 to 25 mph with gusts to 35 mph. 20 to 30 mph with gusts to 40 mph. 15 to 25 mph with gusts to 35 mph.
Expected snowfall: 0 to trace in. 0 to trace in. 0 to trace in.