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 one more day of sunny weather today before a low pressure system quickly moves into the area. Cloud cover should increase ahead of this system during the day today in the form of some thin high clouds. The winds should remain out of the south and southwest and should increase as the system arrives this evening. Snowfall should start tonight and become heavier during tomorrow morning. By tomorrow afternoon snow accumulations could reach 5-12 in above 7000 ft. This system should start to move east of the area tomorrow afternoon and the snowfall and winds should decrease.

Observations:

The strong southwest winds and cooler daytime highs yesterday kept the snow frozen down to at least 7000 ft on Mt. Judah on the sun-exposed southerly aspects. A frozen, breakable sun crust existed on SE-S-SW aspects up to 8000 ft in this area. Farther south on Meiss Ridge the southerly aspects did soften slightly, and a thinner sun crust had started to form on these aspects. In both of these areas, no evidence of warming instabilities existed yesterday. On the northerly aspects sheltered from the wind and sun, several inches of soft snow remained on the surface. Ski cuts and stability tests in these more sheltered areas on Mt. Judah showed a mostly stable snowpack. At the higher elevations and on slopes more exposed to the winds, some small wind slabs had formed on the N-NE-E aspects. In the Judah area, these wind slabs had just started to form by 2 pm. On Meiss Ridge these slabs formed earlier in the day and were slightly larger (pit and photos). In both areas these slabs had not grown large enough to pose a threat to backcountry travelers.

Avalanche Concern #1: Isolated wind slabs

In most areas the wind slabs leftover from last week's storms have bonded quite well to the snowpack below them, and new wind-loading has not created new wind slabs large enough to overload these bonds. However, the snowpack does not gain strength everywhere all at once, and more wind-loading should occur today. Some isolated pockets of unstable wind slabs may exist in complex or extreme terrain on steep wind-loaded N-NE-E and cross-loaded NW and SE aspects near and above treeline. Even though these slabs may be more difficult to trigger, avalanches resulting from failure of these slabs could be large with serious consequences due to their locations. Larger triggers like large cornices or multiple people on a slope will have better chances of causing avalanche activity.

Avalanche Concern #2: Warming Instabilities

Continued southwest winds, more cloud cover, a strong overnight refreeze, and the fact that the snow has already experienced some warming over the last few days should help keep warming instabilities to a minimum today. However, enough melting may occur on the most sun-exposed, southerly slopes for pockets of these instabilities to remain. Small roller balls and loose snow sluffs should make up most of these warming instabilities; however, very isolated slab avalanche activity will remain possible as well. Open, sun-exposed, mid to low elevation SE-S-SW aspects are the best areas for pockets of warming instabilities to form. Instabilities due to daytime warming are unlikely but not impossible on other less sun-exposed aspects and on higher elevation sun-exposed slopes. Less cloud cover and/or warmer temperatures than forecasted could cause these kinds of instabilities to become more widespread today.

The bottom line:

Near and above treeline, very isolated pockets of MODERATE avalanche danger exist on NW-N-NE-E-SE aspects, 37 degrees and steeper. Below treeline, pockets of MODERATE avalanche danger may form on the most sun-exposed SE-S-SW aspects 35 degrees and steeper due to daytime warming.

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	17-19 deg. F.
Max. temperature in the last 24 hours:	21-27 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	35-45 mph
Maximum wind gust in the last 24 hours:	65 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	89-134 inches

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

For 7000-8000 ft:
	Tuesday:	Tuesday Night:	Wednesday:
Weather:	Thin high clouds increasing over the region	Mostly cloudy with snow developing after midnight	Snow in the morning becoming mostly cloudy with occasional snow showers in the afternoon
Temperatures:	34-40 deg. F.	25-30 deg. F.	31-36 deg. F.
Wind direction:	Southwest	South	Southwest
Wind speed:	10-20 mph with gusts between 25 mph and 35 mph	20-35 mph with gusts between 55 mph and 65 mph	15-30 mph with gusts to 55 mph
Expected snowfall:	O in.	up to 2 in.	3-6 in.
For 8000-9000 ft:
	Tuesday:	Tuesday Night:	Wednesday:
Weather:	Thin high clouds increasing over the region	Mostly cloudy with snow developing after midnight	Snow in the morning becoming mostly cloudy with occasional snow showers in the afternoon
Temperatures:	30-34 deg. F.	23-29 deg. F.	27-31 deg. F.
Wind direction:	Southwest	Southwest	Southwest
Wind speed:	25-35 mph with gusts to 55 mph	40-60 mph with gusts to 80 mph	40-60 mph with gusts to 90 mph
Expected snowfall:	O in.	up to 2 in.	5-10 in.