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 29, 2009:


March 29, 2009 at 6:44 am

This morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger may develop on E-SE-S-SW aspects, 37 degrees and steeper in response to daytime warming.


Forecast Discussion:


A cold front is passing through the forecast area today. Strong ridgetop winds and maximum daytime air temperatures up to 20 deg colder than Saturday's highs are expected. Strong winds overnight have kept an air temperature inversion from forming, so the coldest air is at the upper elevations this morning. Very strong westerly ridgetop winds are forecast to gradually decrease to moderate to strong in speed and shift to northwest this afternoon.

Yesterday, the combination of an air temperature inversion and rapid daytime warming caused snow surfaces on E-SE-S-SW aspects to melt very early in the day. On Mt. Judah (Donner Summit area) snow surface melting at the 8,000' level allowed for quality, safe recreation, corn snow conditions on E-SE-S aspects at 9:30 am. By 10:30 am these slopes were becoming very wet and less supportable. The snow surfaces on W-NW-N aspects remained frozen until just after mid day in most areas. No new avalanche activity was reported or observed.

Overnight, remote sensors are reporting below freezing air temperatures above about the 7,500' level. A strong refreeze of yesterday's wet surface snow is expected to have occurred overnight at the upper elevations. Below 7,500' radiational cooling under partly cloudy skies is expected to have allowed for a weak to fair refreeze of the snow surface, largely depending on aspect and snow depth. Today, daytime air temperatures dramatically cooler than the past two days combined with some convectional snow surface cooling from moderate to strong winds will help to limit areas of wet snow instability. However, some pockets of deep wet snow may form by mid afternoon at the lower elevations where air temperatures are warmer and overnight refreeze was not as strong. If you find yourself sinking into wet snow up to the top of your boots, move to a safer location on either a more westerly aspect, northerly aspect, or low angle terrain.


The bottom line:

This morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger may develop on E-SE-S-SW aspects, 37 degrees and steeper in response to daytime warming.


Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 29 deg. F.
Max. temperature in the last 24 hours: 42 to 45 deg. F.
Average wind direction during the last 24 hours: West
Average wind speed during the last 24 hours: 50 mph
Maximum wind gust in the last 24 hours: 85 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 143 inches

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

For 7000-8000 ft:

  Sunday: Sunday Night: Monday:
Weather: Partly cloudy skies. Clear skies. Sunny skies.
Temperatures: 34 to 40 deg. F. 17 to 22 deg. F. 38 to 44 deg. F.
Wind direction: W shifting to NW NE NE
Wind speed: 15 to 25 mph with gusts to 45 mph. Decreasing to 10 to 20 mph with gusts to 30 mph. 10 to 20 mph with gusts up to 30 mph after midnight. 10 to 20 mph with gusts to 30 mph in the morning. Decreasing to around 10 mph in the afternoon.
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Sunday: Sunday Night: Monday:
Weather: Partly cloudy skies. Clear skies. Sunny skies.
Temperatures: 30 to 37 deg. F. 15 to 20 deg. F. 34 to 39 deg. F.
Wind direction: W shifting to NW NE NE shifting to NW
Wind speed: 45 to 55 mph with gusts to 100 mph. Decreasing to 15 to 30 mph with gusts to 60 mph in the afternoon. 20 to 35 mph with gusts to 70 mph. 20 to 30 mph with gusts to 60 mph. Decreasing to 15 to 20 with gusts to 45 mph.
Expected snowfall: O in. O in. O in.