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 warm day with significant cloud cover is expected today with rain and snow showers at times. The greatest amount of cloud cover is forecast over the northern half of the forecast area with more sun breaks expected over the far southern end of the forecast area. Snow level is forecast at 7,000' to 7,500' during the day today, lowering to around 6,000' overnight and down to 5,500' by Thursday afternoon. A few inches of new snow are expected to accumulate tonight and tomorrow. Air temperatures this morning at 8,500' are right around freezing with above freezing air temperatures observed in areas below 7,000'. Ridgetop winds remain out of the west southwest this morning and are increasing from light to moderate in speed. Strong southwest winds are expected later this afternoon and tonight. Cloudy skies and ongoing snow showers are forecast for Thursday.

Observations:

Observations made yesterday morning on Castle Peak (Donner Summit area) revealed new snow amounts from Monday at a trace to 5 inches. The new snow was very wet and high density with a surface rain crust that formed at the end of the storm up to 8,850'. This rain crust was 1 inch thick and very weak. It supported the weight of a skier only on ridge tops and on higher elevation windward aspects. Rain runnels were present at all elevations and aspects in this area. Evidence of some small point release avalanches from yesterday were observed on shaded aspects. The top 1.5 feet of the snowpack was moist or wet and very loose due to the lack of a good refreeze Monday night. No skier triggering of any avalanches occurred during the mid morning hours and stability tests did not indicate any easy failures or propagation (photos, more info).

Observations made mid day yesterday on Jake's Peak (West Shore Tahoe area) revealed that the rain on snow event on Monday created wet snow in the top 30 to 60cm at all elevations traveled (6,800' to 9,150'). By noon the weak melt freeze surface crust that formed Monday night was either fully melted or nearly fully melted to less than 0.5 inch of unsupportable crust remaining at the base of around 4 inches of wet snow with more wet snow below. N-NE aspects above 9,000' were the exception with the melt freeze surface crust remaining supportable at noon. A trace of new snow on top of crust areas existed above 8,500'. Isolated pockets of supportable crust remained in shadows below treeline down to 7,200' on E aspects. Skier triggered wet loose snow avalanches were very easily triggered below 8,300' on E aspect slopes steeper than 35 degrees. This instability was limited to the top 4 inches of wet snow but would entrain more snow with downhill progress (videos, more info).

Primary Avalanche Concern: Warming Instabilities

Increasing cloud cover last night and air temperatures dropping below freezing only at the upper elevations are expected to have allowed for only a weak snow surface refreeze last night. For areas below 7,000', very little to no refreeze is expected to have occurred. At the highest elevation areas above 9,500', air temperatures were considerably colder last night with a stronger snow surface refreeze expected to have occurred on the higher peaks of the Carson Range. Areas of wet snow instability are expected to carry over from yesterday, in many areas below 8,500' due to generally poor snow surface refreeze conditions overnight in the majority of areas. Poorly bonded wet snow up to several feet deep is expected in many low and mid elevation areas today. At the south end of the forecast area where more sun breaks are expected, increased free water production near the snow surface will serve to further fuel the existing wet snow instabilities. Most instability today is expected to take the form of human triggered wet loose snow sluffs. Wet slab avalanches are unlikely but not impossible in isolated areas such as on top of smooth rock slabs. Areas below 8,500' that show little or no evidence of snow surface refreeze last night will be the most suspect.

The bottom line:

Areas of MODERATE avalanche danger are expected at nearly all elevations on E-SE-S-SW-W aspects on slopes 35 degrees and steeper. Pockets of MODERATE danger are expected on NW-N-NE aspects below 8,500' on slopes 35 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:	28 to 33 deg. F.
Max. temperature in the last 24 hours:	36 to 46 deg. F.
Average wind direction during the last 24 hours:	West southwest
Average wind speed during the last 24 hours:	27 mph
Maximum wind gust in the last 24 hours:	66 mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	90 to 156 inches

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

For 7000-8000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Partly cloudy to cloudy skies with scattered rain and snow showers.	Cloudy skies with numerous snow showers.	Cloudy skies with numerous snow showers.
Temperatures:	44 to 48 deg. F.	19 to 26 deg. F.	38 to 44 deg. F.
Wind direction:	SW	SW	SW
Wind speed:	10 to 20 mph increasing to 25 to 35 mph with gusts to 55 mph in the afternoon.	20 to 30 mph with gusts to 65 mph.	15 to 25 mph with gusts to 50 mph.
Expected snowfall:	0 to trace in.	Up to 3 in.	Up to 1 in.
For 8000-9000 ft:
	Wednesday:	Wednesday Night:	Thursday:
Weather:	Partly cloudy to cloudy skies with scattered rain and snow showers.	Cloudy skies with numerous snow showers.	Cloudy skies with numerous snow showers.
Temperatures:	36 to 40 deg. F.	16 to 23 deg. F.	32 to 36 deg. F.
Wind direction:	SW	SW	SW
Wind speed:	20 to 35 mph with gusts to 60 mph. Winds increasing to 30 to 45 mph with gusts to 70 mph in the afternoon.	40 to 50 mph with gusts to 85 mph.	20 to 35 mph with gusts to 55 mph. Gusts decreasing to 45 mph in the afternoon.
Expected snowfall:	0 to trace in.	1 to 3 in.	Up to 2 in.