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 25, 2009:


April 25, 2009 at 7:00 am

Today, the avalanche danger should remain LOW for all aspects and elevations. Some sluffing may occur in the new snow today. Some very small, isolated, human-triggerable winds slabs may exist on wind-loaded aspects near and above treeline.


Forecast Discussion:


Clearer skies, slightly warmer temperatures, and moderate northerly winds should prevail over the forecast area today as the cold front moves off to the east. Winds should shift back to the south and west tonight ahead of a series of low pressure systems moving through the Pacific Northwest. These systems should also bring some clouds, continued cool temperatures, and a chance for some light snow fall to the area early next week.

The forecast area received more snow than expected yesterday with accumulations of 5-8 inches along the Sierra Crest north of Highway 50, 5-10 inches along the crest south of Highway 50, and 6-7 inches in the Carson Range east of Lake Tahoe. Observations from Jake's Peak (West Shore area) and Mt. Judah (Donner Summit area) indicated that this new snow did not bond well to the old, frozen, melt-freeze crust. Snowpit tests and other observations also showed only minor soft slab formation in the new snow and very limited fracture propagation potential. Several human triggered sluffs involving all of the new snow occurred on N-NE-E facing slopes steeper than 35 degrees. While these sluffs did not entrain enough snow to bury a person, they could knock someone over or push a person off course. Some small shooting cracks occurred on Jake's Peak above 8000' on small, steep terrain features (photo). No slab avalanche activity was observed or reported.

The small, isolated wind slabs and cornices that formed during the storm on the N-NE-E aspects should decrease in size today due to the moderate northerly winds that will transport snow from the NW-N-NE-E aspects to the SE-S-SW aspects. As the sun hits the new snow on the SE-S-SW aspects, some small, wet-snow instabilities like roller-balls, pinwheels,and small point-release slides may occur. These should not entrain enough snow to do more than knock a person over or push them somewhere that they did not intend to go. Human-triggered sluffs occurring in the new snow on N-NE-E aspects steeper than 35 degrees should also continue today. However, as the new snow settles and bonds to the old snow surfaces, these sluffs should become less widespread. These sluffs should remain small and should not involve enough snow to bury a person. Most slab avalanche activity should remain unlikely today. A few pockets of small human-triggerable wind slabs and fragile cornices may remain on the most heavily wind-loaded slopes near and above treeline. Slab avalanche activity due to these wind slabs should remain very small and isolated.


The bottom line:

Today, the avalanche danger should remain LOW for all aspects and elevations. Some sluffing may occur in the new snow today. Some very small, isolated, human-triggerable winds slabs may exist on wind-loaded aspects near and above treeline.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 21 deg. F.
Max. temperature in the last 24 hours: 26 deg. F.
Average wind direction during the last 24 hours: Southwest shifting to the north
Average wind speed during the last 24 hours: 22 mph
Maximum wind gust in the last 24 hours: 78 mph
New snowfall in the last 24 hours: 5-10 inches
Total snow depth: 126 inches

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

For 7000-8000 ft:

  Saturday: Saturday Night: Sunday:
Weather: Mostly cloudy in the morning with a chance of snow showers south of Lake Tahoe. Partly cloudy this afternoon Partly cloudy becoming mostly cloudy after midnight Mostly cloudy becoming partly cloudy in the afternoon
Temperatures: 36-44 deg. F. 19-29 deg. F. 38-48 deg. F.
Wind direction: North Southwest West
Wind speed: 10 mph with gusts to 25 mph 10 mph 10 mph
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:

  Saturday: Saturday Night: Sunday:
Weather: Mostly cloudy in the morning with a chance of snow showers south of Lake Tahoe. Partly cloudy this afternoon Partly cloudy becoming mostly cloudy after midnight Mostly cloudy becoming partly cloudy in the afternoon
Temperatures: 26-36 deg. F. 17-27 deg. F. 30-40 deg. F.
Wind direction: North West South shifting to the west
Wind speed: 15-25 mph with gusts to 35 mph 15-25 mph with gusts to 35 mph 15-20 mph decreasing to 10-15 mph with gusts to 30 mph in the afternoon
Expected snowfall: O in. O in. O in.