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 24, 2009:


April 24, 2009 at 7:00 am

Today, the avalanche danger should remain LOW for all aspects and elevations. Some minor sluffing may occur in the new snow today. Some very small, isolated, human-triggerable winds slabs may form on N-NE-E aspects near and above treeline by this afternoon.


Forecast Discussion:


A strong cold front moving through the forecast area should bring scattered, light snow showers through Saturday. Due to the lack of moisture associated with this system only a few inches of snow should accumulate. Temperatures should stay much colder today and tonight before they start to gradually warm up over the weekend. The southwest winds should remain strong until tonight when the front starts to move east of the forecast area. By tomorrow, the winds should diminish and shift to the north and east.

Yesterday marked the last day of continuous above freezing temperatures. By yesterday afternoon, several inches of wet, unconsolidated snow existed on the southerly aspects and on some sun-exposed northerly aspects on Incline Lake Peak in the Mt. Rose area. At 12:30 pm some small, human-triggered roller-balls occurred on a 39 degree SE aspect at 8600'. No other avalanche activity was reported.

As temperatures dropped below freezing last night, the snow should have started to refreeze. As long as the skies stay cloudy and the temperatures stay below freezing, this refreeze should continue. The refreeze will strengthen the snowpack by turning the water in the snowpack into ice that glues the snow together. While the snow remains frozen, avalanche activity in the old snow will remain unlikely.

Even though the winds will transport snow and form some wind slabs on the N-NE-E aspects today, the 1-2 inches of new snow that fell last night combined with up to 2 more inches of snow at the higher elevations today should not be enough for any large, dangerous wind slabs to form.  A few pockets of small human-triggerable wind slabs and fragile cornices may form on the most heavily wind-loaded slopes near and above treeline by this afternoon. Slab avalanche activity due to this wind loading should remain very small and isolated. Most avalanche activity today should be limited to small sluffs occurring in the new snow.


The bottom line:

Today, the avalanche danger should remain LOW for all aspects and elevations. Some minor sluffing may occur in the new snow today. Some very small, isolated, human-triggerable winds slabs may form on N-NE-E aspects near and above treeline by this afternoon.


Andy Anderson - Avalanche Forecaster, Tahoe National Forest


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

0600 temperature: 22 deg. F.
Max. temperature in the last 24 hours: 48 deg. F.
Average wind direction during the last 24 hours: Southwest
Average wind speed during the last 24 hours: 37-50 mph
Maximum wind gust in the last 24 hours: 65-78 mph
New snowfall in the last 24 hours: 0-2 inches
Total snow depth: 121 inches

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

For 7000-8000 ft:

  Friday: Friday Night: Saturday:
Weather: Show showers Cloudy with scattered snow showers Mostly cloudy with scattered snow showers in the morning becoming partly cloudy in the afternoon
Temperatures: 32-40 deg. F. 18-25 deg. F. 34-41 deg. F.
Wind direction: Southwest West shifting to the north Northeast
Wind speed: 20-30 mph with gusts to 45 mph 10-15 mph with gusts to 25 mph 10 mph
Expected snowfall: up to 1 in. trace in. O in.

For 8000-9000 ft:

  Friday: Friday Night: Saturday:
Weather: Show showers Cloudy with scattered snow showers Mostly cloudy with scattered snow showers in the morning becoming partly cloudy in the afternoon
Temperatures: 25-35 deg. F. 13-23 deg. F. 28-38 deg. F.
Wind direction: Southwest West shifting to the north North
Wind speed: 30-45 mph with gusts between 65 and 80 mph 15-25 mph with gusts to 35 mph 10-20 mph with gusts to 30 mph
Expected snowfall: up to 2 in. trace in. O in.