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 weather system that brought cloud cover and anywhere from a trace to 0.4 inches of rain at 8,500' and 0 to 2 inches of new snow at the highest elevations of the forecast area yesterday has moved on. Clear skies and below freezing air temperatures at all elevations have moved in along with high pressure. Ridgetop winds remain out of the west this morning, but have decreased from strong to moderate in speed. Winds are forecast to shift from west northwest to northeast by this afternoon and generally decrease to light in speed. Maximum daytime air temperatures above 7,000' for today are expected in the upper 20s to low 40s, significantly colder than the last several days.

Observations:

Observations made yesterday on Donner Pass (Donner Summit area) revealed no evidence of an overnight refreeze in that area. At 8:30am the top 1.5 to 2 feet of the snowpack was wet snow with free water visible in all wet snow layers at 7,140' on an open SE aspect. Free water production did appear to have decreased during the overnight hours, but without refreeze. At that time, the snow surface was increasing in melt rate and free water production (pit profile, more info). Similar conditions were noted during the mid morning hours on W-NW-N-NE-E aspects on Donner Peak up to the traveled highpoint of 7,600'.

Overnight, remote sensors reported air temperatures falling into the 20s at all locations across the forecast area. For most areas, below freezing air temperatures existed for the 7 to 12 hours leading up to 7am this morning. This is expected to have brought a solid overnight refreeze to the upper portion of the snowpack.

Primary Avalanche Concern: Warming Instability

As air temperatures climb above freezing today and the April amounts of solar radiation warm the snowpack, some areas of warming instability will form today. The greatest areas of instability are expected below 8,000' on slopes with direct sun exposure. With a solid overnight refreeze likely in place and fairly mild air temperatures for today, the entire freeze layer formed last night is not expected to melt today in the vast majority of areas. Wet surface snow on top of a supportable ice layer is expected to last nearly all day today. Human triggered wet loose snow avalanches are the expected form of instability today in steep terrain. Wet slab avalanches are unlikely.

The bottom line:

Early this morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger will form in response to daytime warming on E-SE-S-SW-W aspects on slopes 37 degrees and steeper.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	21 to 28 deg. F.
Max. temperature in the last 24 hours:	38 to 42 deg. F.
Average wind direction during the last 24 hours:	West
Average wind speed during the last 24 hours:	49 mph
Maximum wind gust in the last 24 hours:	93 mph
New snowfall in the last 24 hours:	0 to 2 inches
Total snow depth:	108 to 175 inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Mostly sunny skies.	Clear skies.	Partly cloudy skies.
Temperatures:	35 to 43 deg. F.	25 to 32 deg. F.	49 to 56 deg. F.
Wind direction:	W shifting to NE	NE shifting to SE	W
Wind speed:	5 to 10 mph.	Around 10 mph.	Up to 10 mph.
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:	Mostly sunny skies.	Clear skies.	Partly cloudy skies.
Temperatures:	26 to 32 deg. F.	25 to 32 deg. F.	41 to 49 deg. F.
Wind direction:	W shifting to NE	E	NE shifting to W
Wind speed:	15 to 25 mph with gusts to 40 mph. Winds shifting and decreasing to 15 to 20 mph in the afternoon.	10 to 20 mph with gusts to 35 mph.	10 to 15 mph.
Expected snowfall:	O in.	O in.	O in.