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.

A strong low pressure dropping out of the Gulf of Alaska should begin to push the high pressure over the forecast area towards the east. The winds have already shifted back to the southwest and increased ahead of this storm. The winds should continue to increase as this low moves closer. The forecast calls for sustained ridgetop winds above 50 mph with gusts over 110 mph by tomorrow afternoon. Cloud cover should also start to increase later today and become widespread by tonight. By tomorrow afternoon/evening precipitation should start to fall. Snow levels should start between 7500 and 8000 ft during the day tomorrow and lower during the storm. Check the Reno NWS site for more details and updates on the approaching storm.

Observations:

Snowpit data and layer bonding tests from Jake's Peak (West Shore area) and Horse Canyon (Bear Valley area) showed continued settlement in the recent snow. Moderate force did still break the bonds between the graupel layer near the base of the recent snow and the snow above it on a NE facing aspect on Jake's Peak. However, ski cuts on test slopes in this area did not produce any signs of instabilities on the N-NE facing slopes where this graupel layer still exists. 4-8 inches of soft snow remained on the N-NE facing aspects on Jake's Peak above 7500'. Above 8000', a thin, barely noticeable crust existed below this snow. Below 8000' this crust became thicker and more widespread leading to more "dust on crust" conditions on the lower elevation slopes. Melt-freeze cycles over the last few days have quickly transformed most of the snow on the more sun-exposed E-SE-S aspects below 8000' into melt-freeze snow. On Jake's by noon yesterday, SE facing slopes below 8000 ft had 1-2 inches of soft corn snow sitting on top of a supportable melt-freeze crust. Above 8000' some of the snow on these sun exposed aspects has not fully changed to melt-freeze snow and remains wet and sticky. Remote sensors indicated that temperatures in most areas below 8300' remained above freezing last night. Even though the snowpack should have released enough heat into the atmosphere to refreeze some clouds and the warmer overnight temperatures should have caused a weaker refreeze last night.

Avalanche concern #1: Warming instabilities

The intense March sunshine, a weaker overnight refreeze, and daytime highs in the upper 40's and low 50's, should allow enough warming and melting to occur today for wet-snow instabilities to form on sun-exposed aspects. Most of these instabilities should present as roller balls and point-release slides; however, some slab avalanches could occur especially on steep, SE-facing slopes where the recent snow has not fully transformed from cold, new snow into melt-freeze snow (corn). These warming instabilities should be most common on SE-S-SW aspects below 9000', but they are not impossible at some of the higher elevations on the most sun-exposed slopes and on some lower elevation northerly aspects. More widespread cloud cover than forecast today would help keep most of these wet snow instabilities in check.

Avalanche concern #2: Wind Slabs

A few isolated areas of human-triggerable  wind slabs could still exist on steep, wind loaded, NW-N-NE aspects near and above treeline north of Lake Tahoe. These slabs should be more difficult to trigger today due to settlement in the snowpack. However, the right trigger in the right spot could still cause them to fail. Steep, complex terrain with unsupported snowfields, cliffs, convexities and other complicated terrain features will hold the most potential for these lingering slabs.

The bottom line:

Pockets of MODERATE avalanche danger will form on the sun-exposed E-SE-S-SW-W aspects on slopes 35 degrees and steeper due to daytime warming today. Near and above treeline a few isolated pockets of MODERATE danger may still exist on the most wind-loaded NW-N-NE aspects steeper than 37 degrees north of Lake Tahoe.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	30-34 deg. F.
Max. temperature in the last 24 hours:	42-49 deg. F.
Average wind direction during the last 24 hours:	East until 2 pm yesterday, then southwest
Average wind speed during the last 24 hours:	East: 20 mph | Southwest: 30-35 mph
Maximum wind gust in the last 24 hours:	51 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	84-123 inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Partly sunny with clouds increasing in the afternoon.	Mostly cloudy	Mostly cloudy with a 30-40% chance of rain by the afternoon. Snow levels between 7500' and 8000'.
Temperatures:	43-50 deg. F.	27-33 deg. F.	44-49 deg. F.
Wind direction:	Southwest	Southwest	Southwest
Wind speed:	10-15 mph with gusts to 30 mph increasing to 20-30 mph with gusts to 50 mph in the afternoon	20-30 mph with gusts to 50 mph	20-30 mph with gusts to 60 mph increasing to 30-45 mph with gusts to 75 mph in the afternoon
Expected snowfall:	O in.	O in.	Rain -.05 in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Partly sunny with clouds increasing in the afternoon.	Mostly cloudy	Mostly cloudy with a 40% chance of snow by the afternoon.
Temperatures:	43-49 deg. F.	22-29 deg. F.	42-45 deg. F.
Wind direction:	Southwest	Southwest	Southwest
Wind speed:	25-35 mph with gusts to 65 mph	30-45 mph with gusts to 85 mph	35-50 mph with gusts to 85 mph increasing to 45-55 mph with gusts to 110 mph
Expected snowfall:	O in.	O in.	less than .5 in.