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 storm systems that impacted the forecast area yesterday and last night have tapered off early this morning. Yesterday, snow level was much lower and snowfall intensity much higher than forecast. This lead to 10 to 20 inches of new snow accumulation above 6,700' during the day yesterday. Last night, an additional 14 to 21 inches of new snow accumulated bringing the 24 hour new snow accumulation to 20 to 32 inches across the forecast area. New snow amounts since Tuesday are 25 to 65 inches above 6,700'.

Remote sensors are reporting air temperatures above 8,200' in the low teens to low 20s this morning across the forecast area. Maximum daytime air temperatures are forecast to warm into the low 20s to low 30s today for areas above 7,000'. Ongoing snow showers are forecast for an additional 1 to 4 inches of new snow accumulation today. Ridgetop winds remain out of the southwest and are decreasing in speed this morning. Strong winds over the past several days have decreased to moderate in speed this morning and are forecast to further decrease to light to moderate in speed this afternoon. Colder air moving into the region behind the departing storm system will drop air temperatures into the single digits and teens tonight above 7,000'. Daytime highs in the teens and 20s and expected tomorrow above 7,000'. Continued light to moderate speed west winds are expected. Snow showers are forecast to continue through the weekend.

Recent Observations:

Natural and intentionally human triggered avalanches with snowpack failure occurring at the base of wind slabs 1.5 to 2 feet deep were observed yesterday in wind loaded areas on the East Ridge of Tamarack Peak (Mount Rose area). These avalanches occurred at 9,400' on a N aspect 35 to 40 degree slope in near treeline terrain. The avalanches measured 75' to 100' wide and ran 200' to 250' down slope (photos, videos, more info). Observations made yesterday on Mt. Judah (Donner Summit area) revealed that the persistent weak layer of crust and faceted snow was buried nearly 6 feet below the snow surface prior to last nights additional snowfall and bridged by a high density snow layer making it difficult to trigger (pit profile, more info). Observations made yesterday along Frog Lake Ridge (Carson Pass area) indicated ongoing instability of this same persistent weak layer that was buried only 2 to 3 feet deep in the snowpack prior to last nights new snowfall. Snowpit tests on this layer indicated that once collapse of the weak layer was triggered, propagation along that weak layer is likely to occur (videos, more info). This indication of likely propagation is similar to recent observations from around the forecast area over the past 2 to 4 weeks and continues to fuel concerns for deep slab avalanches.

Today's Primary Avalanche Concern: Wind Slabs and Storm Slabs

With last night's storm system tapered down and departing the area, the best window for widespread natural avalanche activity has past. That said, cornices are large and weak in many areas. Naturally occurring cornice collapse could still trigger a natural avalanche today. Ongoing instability of recently created wind slabs and storm slabs is expected. Human triggered avalanches remain likely today with large destructive avalanches possible. Warming air temperatures yesterday and high intensity snowfall rates last night are expected to have created weak layers within the storm snow that will persist today in both wind protected areas and wind loaded areas. 

Today's Secondary Avalanche Concern: Persistent Deep Slabs

The persistent weak layer of crust and facets that exists above and below treeline on most NW-N-NE aspects and some E aspects was heavily loaded by new snow and rain through this storm cycle. Additional rapid loading by high intensity snowfall occurred last night. Human triggering of this weak layer leading to deep slab avalanches is of greatest concern along the Sierra Crest from the Echo Summit area southward and along the Carson Range on the east side of Lake Tahoe. In these areas this weak layer is closer to the snow surface and easier to trigger. Along the northern Sierra Crest, this weak layer is now buried 6+ feet deep, bridged by a very strong and supportable layer of snow, and more difficult to trigger at this time. Any avalanche activity involving failure of this weak layer will cause very large and destructive avalanches as the overlying slab is several feet thick and composed of high density snow.

The bottom line:

Both above and below treeline, avalanche danger is CONSIDERABLE on NW-N-NE-E-SE aspects on slopes 35 degrees and steeper. For all other areas, avalanche danger is MODERATE with pockets of CONSIDERABLE danger on slopes 35 degrees and steeper. Due to the combination of several feet of new snow and persistent deep slab instability, large destructive avalanches are possible today.

Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	14 to 21 deg. F.
Max. temperature in the last 24 hours:	29 to 34 deg. F.
Average wind direction during the last 24 hours:	Southwest
Average wind speed during the last 24 hours:	35 mph
Maximum wind gust in the last 24 hours:	74 mph
New snowfall in the last 24 hours:	20 to 32 inches
Total snow depth:	56 to 93 inches

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

For 7000-8000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:	Mostly cloudy skies with scattered snow showers. Snow showers increasing and becoming numerous by afternoon.	Cloudy skies with snow showers.	Cloudy skies with snow showers.
Temperatures:	26 to 32 deg. F.	11 to 16 deg. F.	17 to 24 deg. F.
Wind direction:	S shifting to NW to N	W	W
Wind speed:	20 to 25 mph with gusts to 35 mph in the morning, shifting and decreasing to 10 to 15 mph.	Light winds increasing to 5 to 15 mph.	10 to 20 mph with gusts up to 30 mph in the afternoon.
Expected snowfall:	2 to 4 in.	1 to 3 in.	1 to 3 in.
For 8000-9000 ft:
	Saturday:	Saturday Night:	Sunday:
Weather:	Mostly cloudy skies with scattered snow showers. Snow showers increasing and becoming numerous by afternoon.	Cloudy skies with snow showers.	Cloudy skies with snow showers.
Temperatures:	21 to 26 deg. F.	6 to 12 deg. F.	16 to 22 deg. F.
Wind direction:	S shifting to W	W	W
Wind speed:	30 to 35 mph with gusts to 50 mph in the morning, shifting and decreasing to 10 to 15 mph with gusts to 25 mph in the afternoon.	10 to 15 mph.	15 to 25 mph with gusts to 40 mph.
Expected snowfall:	2 to 4 in.	1 to 3 in.	1 to 3 in.