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.

This advisory was posted on April 13, 2008 6:55 AM

A map of the SAC forecast area is available on our home page.

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Today's Advisory:
Early this morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger will develop in sun exposed areas, 38 degrees and steeper in response to daytime warming.

Warm air temperatures are expected to remain in place over the forecast area through Monday morning before a change is in store. Yesterday's warm air temperatures and light winds have allowed a significant air temperature inversion to set up overnight. This morning, remote sensors are reporting air temperatures at the 6,000' to 6,500' level at or slightly below freezing. Air temperatures above 8,000' are in the low to mid 40s. Overall slightly colder air temperatures have been reported this morning in the Carson Pass area. Ridgetop winds are expected to remain light this morning before shifting to the southwest and becoming light to moderate in speed this afternoon

Yesterday, the warmest air temperatures so far this spring were observed across the forecast area. Observations made on Secret Peak and Jake's Peak (West Shore Tahoe area) indicated that significant free water production occurred within the upper portion of the snowpack on all aspects and at all elevations in the area (6,700' to 9,200'). With significant melt-freeze conditions occurring over the past 7 weeks, the snowpack was able to handle the increase in free water production with only minimal and spotty signs of wet snow instability observed. On Secret Peak, a small skier triggered wet snow sluff was observed at 11:20 am on an E aspect, 38 degree slope convexity at 8,000'. On Jake's peak, ski penetration approached 3 to 4 inches in wet snow on E-NE aspects at 1 pm. However, no wet snow sluffs or other signs of instability were observed, even in areas 38 degrees and steeper. Observations made near Kirkwood ski area reported that shallow skier trigger surface sluffs occurred in wet, unconsolidated 1 week old snow on steep NE aspects around 9,500'.

Today, the amount of overnight refreeze of the snowpack will be deceiving. At lower elevation trail heads, the snow surface will be well frozen this morning due to a combination of near or below freezing air temperatures and radiational cooling of the snowpack overnight. With warmer air temperatures at the upper elevations, only a thin and superficial refreeze of the snow surface is expected to have occurred from radiational cooling. Once the sun begins to melt the snow surface, this thin melt-freeze crust will quickly disappear. This will expose the 1 to 2 feet of wet snow in the upper portion of the snowpack that formed yesterday. Conditions will change from frozen to mush much faster today at the upper elevations than at the lower elevations. Human trigger wet snow sluffs are expected to occur again today in pockets of sun exposed terrain 38 degrees and steeper. Deeper wet slab avalanches are unlikely but not impossible at this time.

The bottom line: Early this morning, avalanche danger is LOW for all elevations and aspects. Pockets of MODERATE danger will develop in sun exposed areas, 38 degrees and steeper in response to daytime warming.

Brandon Schwartz, Avalanche Forecaster

Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 43 deg. F
Max. temperature at Sierra Crest past 24 hours: 51 to 59 deg. F.
Average wind direction at Sierra Crest past 24 hours: Southwest becoming light and variable
Average wind speed at Sierra Crest past 24 hours: 10 mph
Maximum wind gust at Sierra Crest past 24 hours: 26 mph
New snowfall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 70 inches

Mountain Weather Forecast For Today:
Sunny and even warmer.
Temperature forecast for 8,000 to 9,000 feet: 50 to 59 deg. F
Ridgetop winds forecast for the Sierra Crest: Light winds becoming southwest at 10 to 15 mph with gusts to 35 mph in the afternoon.
Snowfall expected in the next 24 hours: 0 inches

2 Day Mountain Weather Forecast:

7000 to 8000 Feet:

Today, sunny skies with daytime highs 59 to 67 deg. F. Light winds becoming southwest around 10 mph in the afternoon.

Tonight, mostly clear skies with overnight lows 36 to 41 deg. F. Southwest winds at 10 to 20 mph with gusts to 35 mph.

For Monday, partly cloudy skies with daytime highs 46 to 54 deg. F. Southwest winds at 15 to 25 mph with gusts to 40 mph. Winds shifting to west at 30 to 40 mph with gusts to 60 mph in the afternoon.

Above 8000 Feet:

Today, sunny skies with daytime highs 50 to 59 deg. F. Light winds becoming southwest at 10 to 15 mph with gusts to 35 mph in the afternoon.

Tonight, mostly clear skies with overnight lows 34 to 40 deg. F. Southwest winds at 30 to 45 mph with gusts to 60 mph, increasing to 75 mph after midnight.

For Monday, partly cloudy skies with daytime highs 37 to 46 deg. F. Southwest winds at 35 to 50 mph with gusts to 100 mph.

The bottom line:

Andy Anderson - Avalanche Forecaster, Tahoe National Forest

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

0600 temperature:	deg. F.
Max. temperature in the last 24 hours:	deg. F.
Average wind direction during the last 24 hours:
Average wind speed during the last 24 hours:	mph
Maximum wind gust in the last 24 hours:	mph
New snowfall in the last 24 hours:	O inches
Total snow depth:	inches

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

For 7000-8000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.
For 8000-9000 ft:
	Sunday:	Sunday Night:	Monday:
Weather:
Temperatures:	deg. F.	deg. F.	deg. F.
Wind direction:
Wind speed:
Expected snowfall:	O in.	O in.	O in.