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.

After another mostly clear night, cloud cover should start to increase over the forecast area today as a low pressure system approaches the region. This system should bring some precipitation with it. Light showers could start as early as this afternoon. By tonight the precipitation will become more widespread and heavier. Most of this precipitation should fall as rain until a cold front associated with this system reaches the Central Sierra tomorrow. Snow levels should start near 8500 ft and remain there until tomorrow when they should fall to around 7500 ft. The forecast calls for 1.5 inches of precipitation by the end of the day tomorrow. At the elevations above 8500 ft. 10-12 inches of new snow could accumulate. The southwest winds should also start increasing ahead of this storm. They should remain strong through tomorrow.

Observations:

Yesterday more sunshine, less wind, and warmer temperatures than expected led to more warming instabilities than expected. Observations on Castle Peak (photos and more info) and Echo Peak (photos and more info), showed some small, human-triggerable, wet snow sluffs and roller balls on the southerly aspects at all elevations. In both of these areas, the instabilities did not entrain enough snow to cause serious consequences except in areas with terrain traps. Some areas on the northerly and easterly aspects in both of these places still held recent snow that had not fully transitioned to melt-freeze snow. In these areas larger roller balls and sluffs occurred. A strong, thick, and frozen melt-freeze crust existed underneath the wet surface snow in both of these areas.

Primary Avalanche Concern: Warming Instabilities

Mostly clear skies and temperatures near freezing should have allowed the snowpack to radiate enough heat out into space for a moderate refreeze to occur in most areas. As the sun hits the slopes today and the temperatures climb back into the mid to upper 40's, melting will start to produce free water in the snowpack. When the clouds increase this afternoon, melting due to the sun and warm air temperatures should begin to slow down. If, however, rain also accompanies these clouds it will allow the melting to continue. Rain will cause melting and will add more water to the snowpack on all aspects. Sun, warm temperatures, rain, and a weaker overnight refreeze should allow the melting that occurs today to penetrate deeper into the snowpack and create a thicker layer of soft, wet snow on the surface. Wet snow instabilities like roller balls and wet snow sluffs will again become possible today. The thicker layer of wet snow will allow these instabilities to grow slightly larger today. They could start to push people into terrain traps with more serious consequences. Some wet slab avalanches may again become possible especially in areas that receive rain where the recent snow has not fully transitioned to melt-freeze snow. As the rain showers increase this evening and tonight, wet snow instabilities will become more widespread.

The bottom line:

This morning the avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE avalanche danger should form on all aspects due to daytime warming and rain this afternoon and tonight. As the rain showers increase this evening and tonight, wet snow instabilities will become more widespread.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	33-36 deg. F.
Max. temperature in the last 24 hours:	47-54 deg. F.
Average wind direction during the last 24 hours:	West Southwest
Average wind speed during the last 24 hours:	20 mph
Maximum wind gust in the last 24 hours:	35 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	94-159 inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Partly cloudy this morning becoming mostly cloudy with a slight chance of rain this afternoon. Snow level 8500 ft.	Rain	Rain and snow. Snow level lowering to 7500 ft.
Temperatures:	48-54 deg. F.	31-37 deg. F.	40-46 deg. F.
Wind direction:	Southwest	Southwest	Southwest
Wind speed:	10-15 mph with gusts to 35 mph increasing to 15-25 mph with gusts to 50 mph	15-25 mph with gusts to 55 mph	20-30 mph with gusts to 55 mph
Expected snowfall:	Rain: trace in.	Rain: 1 in.	Above 7500 ft.: up to 4 in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Partly cloudy this morning becoming mostly cloudy with a slight chance of rain this afternoon. Snow level 8500 ft.	Rain and snow. Snow level 8500 ft.	Snow.
Temperatures:	40-44 deg. F.	29-35 deg. F.	34-40 deg. F.
Wind direction:	Southwest	Southwest	Southwest
Wind speed:	15-25 mph with gusts to 45 mph increasing to 30-45 mph with gusts to 65 mph in the afternoon	25-35 mph increasing to 30-45 mph after midnight with gusts to 75 mph	25-40 mph with gusts to 75 mph
Expected snowfall:	Trace in.	Above 8500 ft: up to 6 in.	up to 4 in.