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 February 25, 2013:


February 25, 2013 at 7:30 am

Avalanche danger is LOW for all elevations and aspects. Finding an isolated unstable wind slab is unlikely but not impossible today in near treeline or above treeline terrain. Normal caution is advised.


Forecast Discussion:


A weather system is passing by to the north of the forecast area today. As a result, ridgetop winds shifted to the west last night and air temperatures are a few degrees warmer this morning. A few clouds from the tail end of the passing system will pass over the region today, mainly over the northern portion of the forecast area. A gradual warming trend continues today with maximum daytime air temperatures expected at 7 to 10 degrees warmer than yesterday for areas above 7,000'. Moderate speed westerly ridgetop winds for today are forecast to become strong tonight as they shift to the northwest and then to the northeast after midnight. Similar air temperatures and decreasing northeast winds are forecast for tomorrow.

Recent Observations:

Observations made yesterday on Silver Peak (Pole Creek area) revealed hard wind slabs in near and above treeline areas on all aspects. For the most part, formal and informal tests indicated that these slabs were stable. A few isolated snowpit tests indicated the possibility of difficult to trigger, but theoretically possible instability lingering on N aspects at treeline. Slab thickness varied greatly from 3 to 6 inches across most slopes, often over very short distances (pit profile, more info). Recent observations from a variety of locations around the forecast area over the past few days have also indicated stable snowpack conditions (videos, photos, pit profiles, more info).

Avalanche Problem #1: Wind Slabs

Strong to gale force winds shifting back and forth from SW to NE have occurred over the past few days. Observations thus far have shown that wind slabs that formed on most aspects are generally stable. On a regional scale, triggering a wind slab avalanche is unlikely today. That said, an isolated unstable wind slab may exist in recently wind loaded or cross loaded near treeline or above treeline terrain. Upper elevation complex or extreme terrain near the Sierra Crest is the most likely location for the existence of an unstable wind slab today.

A small amount of wet surface snow will likely form today in wind protected areas at mid and lower elevations on southerly aspects. While a few small roller balls may occur, wet snow avalanche activity remains unlikely.


The bottom line:

Avalanche danger is LOW for all elevations and aspects. Finding an isolated unstable wind slab is unlikely but not impossible today in near treeline or above treeline terrain. 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: 22 to 27 deg. F.
Max. temperature in the last 24 hours: 30 to 36 deg. F.
Average wind direction during the last 24 hours: Northeast shifting to west
Average wind speed during the last 24 hours: NE 25 mph | W 20 mph
Maximum wind gust in the last 24 hours: NE 43 mph | W 35 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 57 to 83 inches

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

For 7000-8000 ft:

  Monday: Monday Night: Tuesday:
Weather: Mostly sunny to partly cloudy skies. Partly cloudy skies, becoming clear. Sunny skies.
Temperatures: 37 to 43 deg. F. 20 to 27 deg. F. 38 to 45 deg. F.
Wind direction: W NW shifting to NE E
Wind speed: 15 to 20 mph with gusts to 30 mph. 15 to 20 mph with gusts to 35 mph, shifting and decreasing to 10 to 15 mph with gusts to 30 mph after midnight. 10 to 15 mph. Gusts to 25 mph in the morning.
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Monday: Monday Night: Tuesday:
Weather: Mostly sunny to partly cloudy skies. Partly cloudy skies, becoming clear. Sunny skies.
Temperatures: 30 to 37 deg. F. 20 to 27 deg. F. 30 to 38 deg. F.
Wind direction: W NW shifting to NE NE
Wind speed: 20 to 30 mph with gusts to 45 mph. 30 to 40 mph with gusts to 60 mph, shifting and decreasing to 20 to 30 mph with gust to 45 mph after midnight. 15 to 25 mph. Gusts to 40 mph in the morning.
Expected snowfall: O in. O in. O in.