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.

The forecast calls for rain and snow to begin over the forecast area around 10-11 am this morning. The south-southwest flow associated with this system should continue to pull warm air into the area keeping snow levels between 7500' and 8000' through tonight. A cold front should start to impact the forecast area tomorrow causing snow levels to drop to around 6000' by the afternoon. Precipitation totals should measure between .5 and 1 inches in the next 24 hours. Below 8000' most of this precipitation should fall as rain. Above 8000' most of it should fall as snow. Strong south-southwest winds will accompany the onset of this storm with sustained ridgetop winds between 40 and 70 mph for the next 24 hours. Ridgetop gusts could exceed 120 mph. The forecast calls for stormy weather through next week.

Yesterday, observations in the Mt. Rose area and on the West Shore found a few inches of soft unconsolidated snow above 7500' on shaded, wind-protected, northerly aspects. A mix of breakable sun and wind crusts, hard wind slabs, wind scoured snow, and melt / freeze snow exists on the snow surface on most other aspects. Layer bonding tests in the Mt. Rose area showed that the most recent snow, the layers around the Feb. 22-23 rain crust, and snowpack above the Jan. 22-23 crust / facet layers have continued to gain strength. These tests as well as others during that last few days indicated that the Jan. 22-23 crust / facet layer has started to gain strength in some areas but remains weak in other areas.

The primary avalanche concern today will be rain on snow. The rain that falls over the next 24 hours will erode some of the strength gained by the layers in the upper snowpack over the last few days. The rain will weaken the snowpack in 3 ways. First, it will melt the bonds that have formed between the snow grains and between the layers in the snowpack. Second, it will lubricate layers that could serve as bed surfaces in the snowpack. Third, it will add more weight to the snowpack while making the snowpack weaker. Natural and human triggered avalanche activity could become possible due to today's rain.

The second avalanche concern today will be new wind slabs above 8000' formed by the south southwest winds and the new snow. These wind slabs will form quickly on leeward slopes today. By this afternoon and evening these wind slabs could be fragile enough to break in response to a person's weight. The largest and most widespread wind slabs will form on open NW-N-NE aspects above 8000'.

The third avalanche concern today will continue to be deep slabs due to failure of the crust / facet layer at the base of the Feb. snow. Variability in the strength of this layer will make it harder to predict what will cause it to fail and where that failure might occur. Northerly aspects between 7400'-8700' that have steep, open, unsupported (for example: a cliff at the bottom of a steep slope), and rocky terrain will hold the best potential for triggering this persistent weak layer. Watch out for likely trigger points where a shallower snowpack exists, because it will be easier to break this layer in these locations. Once this layer starts to break, the fracture could propagate out into areas where a much thicker slab exists and result in very deep avalanches.

The bottom line:

The avalanche danger will rise to CONSIDERABLE  on slopes steeper than 35 degrees for all aspects and elevations that receive rain today. Above the rain line the avalanche danger is MODERATE with pockets of CONSIDERABLE developing on the on NW-N-NE aspects, 35 degrees and steeper 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:	33 deg. F.
Max. temperature in the last 24 hours:	35-41 deg. F.
Average wind direction during the last 24 hours:	South Southwest
Average wind speed during the last 24 hours:	35 mph
Maximum wind gust in the last 24 hours:	90 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	123 inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Rain and snow developing after 10 am. Snow level between 7500-8000 ft.	Rain and snow with snow level around 7500 ft.	Rain and snow becoming mostly snow by the afternoon. Snow level dropping to 6000 ft.
Temperatures:	42-48 deg. F.	26-33 deg. F.	33-40 deg. F.
Wind direction:	South	South	South
Wind speed:	20-35 mph with gusts to 50 mph	25-40 mph with gusts to 65 mph	25-35 mph with gusts to 85 mph decreasing to gusts to 60 mph in the afternoon
Expected snowfall:	Rain -> .25-.5 in. Snow -> 1-4 in.	Rain -> .25-.5 in. Snow ->1-4 in.	Snow -> 5-10 in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Snow with some rain near 8000 ft. developing after 10 am. Snow level between 7500-8000 ft.	Snow with some rain around 8000 ft before midnight. Snow level around 7500 ft.	Snow
Temperatures:	35-41 deg. F.	21-28 deg. F.	31-37 deg. F.
Wind direction:	South	South	South
Wind speed:	40-55 mph with gusts to 85 mph increasing to 110 mph this afternoon	50-70 mph with gusts to 120 mph	55-70 mph with gusts to 120 mph decreasing to 35-50 mph with gusts to 80 mph in the afternoon
Expected snowfall:	2-6 in.	4-8 in.	6-12 in.