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 January 22, 2011:


January 22, 2011 at 8:00 am

The avalanche danger should remain LOW for all elevations and aspects today. Continue to use normal caution when traveling in the backcountry.


Forecast Discussion:


The strong high pressure ridge over the forecast area shows no signs of departing. After some clouds this morning, mostly sunny and dry weather should continue over the next 24 hours across the region. Today's temperatures should not climb as high as yesterday due to a cold front passing east of the area. This will also allow the winds to increase and shift more towards the north and east today and tonight. By tomorrow temperatures should start to climb again and the winds should start to decrease.

Observations:

A week of spring-like weather and consistent melt-freeze cycles have created excellent corn snow on the southerly aspects. On the south slopes of Mt. Tallac above Lily Lake (photo) and on Tamarack Peak yesterday, 2-3 inches of soft, wet snow has formed on top of a supportable frozen layer on sun-exposed southerly aspects. Similar conditions existed in the Donner Summit area and the Mt. Rose area the day before. In all of these areas, not enough melting occurred for water to saturate any layers in the snowpack or for wet snow instabilities to form over the last two days due to solid overnight refreezes, low sun angles, and well established drainage channels in the snowpack. On the northerly aspects, a firm, frozen crust exists in most areas with a few patches of softer snow in some areas. 

Avalanche Concerns:

Another strong overnight refreeze should have occurred last night due to overnight temperatures below or near freezing in most areas and a mostly clear night sky that allowed the snowpack to radiate heat out into space. With cooler temperatures and stronger north and east winds forecast for today, less melting should occur, and what melting does occur should take longer. The melting that happens today should be enough to soften the snow surface on the most sun-exposed southerly aspects, but it should not release enough water into the snowpack for dangerous wet snow instabilities to form. Some small, isolated, shallow, wet, loose sluffs could still occur on the most sun-exposed slopes especially if the temperatures climb higher than forecasted. Most northerly aspects should remain frozen today. Continue to travel with caution in the backcountry today.


The bottom line:

The avalanche danger should remain LOW for all elevations and aspects today. Continue to use normal caution when traveling in the backcountry.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 28-32 deg. F.
Max. temperature in the last 24 hours: 49-56 deg. F.
Average wind direction during the last 24 hours: Northeast
Average wind speed during the last 24 hours: 15 mph
Maximum wind gust in the last 24 hours: 39 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 60-89 inches

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

For 7000-8000 ft:

  Saturday: Saturday Night: Sunday:
Weather: Partly cloudy this morning becoming sunny this afternoon Clear Sunny in the morning becoming partly cloudy in the afternoon
Temperatures: 40-45 deg. F. 25-33 deg. F. 43-48 deg. F.
Wind direction: Northeast shifting to the East East East
Wind speed: 10-20 mph with gusts to 30 mph 10-20 mph with gusts to 30 mph around 10 mph
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Saturday: Saturday Night: Sunday:
Weather: Partly cloudy this morning becoming sunny this afternoon Clear Sunny in the morning becoming partly cloudy in the afternoon
Temperatures: 35-40 deg. F. 25-30 deg. F. 35-43 deg. F.
Wind direction: Northeast shifting to the East East East shifting to the Northwest
Wind speed: 15-25 mph with gusts to 50 mph increasing to 20-35 mph with gusts to 60 mph in the afternoon 20-35 mph with gusts to 65 mph 15-25 mph with gusts to 35 mph decreasing to 10-15 mph in the afternoon
Expected snowfall: O in. O in. O in.