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 April 7, 2009:

April 7, 2009 at 7:00 am

This morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger could form this afternoon below treeline on all aspects, 35 degrees and steeper in response to a combination of daytime warming and light rain.

Forecast Discussion:

The low-pressure system off the CA coast should reach the forecast area today. Cloud cover and southerly winds should begin to increase as this system moves onshore this morning. By this afternoon some scattered showers could develop over the forecast area. Initially some light rain could fall below 7500' due to a warm air mass ahead of this system. However, snow levels should quickly drop to 5000' by tonight. The forecast calls for 2-4 inches of snow in the Sierra overnight. This system should move east of the area tomorrow leaving only some isolated snow showers and clouds over the forecast area for Wednesday.

Yesterday, the sun-exposed E-SE-S-SW-W aspects softened quickly. By 11 am 2-3 inches of soft corn snow existed on the snow surface on those aspects. By 3 pm 6-8 inches of wet snow had formed on the surface on those aspects. Even though temperatures remained well above freezing overnight last night, the skies stayed mostly clear and should have allowed the snow to radiate enough heat into the night sky for most of yesterday's soft snow to refreeze.

Today, the increasing clouds should limit the amount of sun that reaches the snow surface. Some softening of the snow surface could occur on the sun-exposed E-SE-S aspects this morning while skies remain clear. Less sunshine means less melting of the snowpack. This lack of melting combined with well established drainage channels in the snowpack should prevent any major wet-snow instabilities from forming today. Below 7500' some slopes could receive light rain this afternoon. The combination of warming this morning, a weak overnight refreeze, and added warmth plus water in the form of rain could cause some wet snow instabilities to form on these slopes.


The bottom line:

This morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger could form this afternoon below treeline on all aspects, 35 degrees and steeper in response to a combination of daytime warming and light rain.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature: 38 deg. F.
Max. temperature in the last 24 hours: 52 deg. F.
Average wind direction during the last 24 hours: Southeast
Average wind speed during the last 24 hours: 14 mph
Maximum wind gust in the last 24 hours: 33 mph
New snowfall in the last 24 hours: O inches
Total snow depth: 136 inches

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

For 7000-8000 ft:
  Tuesday: Tuesday Night: Wednesday:
Weather: Increasing clouds throughout the day with some scattered showers occurring by this afternoon. Snow level 7500'. Snow showers in the evening becoming scattered after midnight Cloudy in the morning becoming mostly cloudy in the afternoon with a chance of snow showers throughout the day
Temperatures: 48-54 deg. F. 22-28 deg. F. 34-40 deg. F.
Wind direction: South Southwest Southwest shifting to the west
Wind speed: 10-15 mph with gusts to 30 mph 10-15 mph with gusts to 30 mph 10-15 mph with gusts to 30 mph increasing to 15-25 mph with gusts to 40 mph in the afternoon
Expected snowfall: O in. 1-4 in. O in.

For 8000-9000 ft:
  Tuesday: Tuesday Night: Wednesday:
Weather: Increasing clouds throughout the day with some scattered snow showers occurring by this afternoon. Snow showers in the evening becoming scattered after midnight Cloudy in the morning becoming mostly cloudy in the afternoon with a chance of snow showers throughout the day
Temperatures: 38-48 deg. F. 13-20 deg. F. 29-35 deg. F.
Wind direction: South Southwest West
Wind speed: 20-30 mph with gusts to 45 mph 15-25 mph with gusts to 40 mph 20-30 mph with gusts to 55 mph
Expected snowfall: O in. 2-5 in. O in.