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 Avalanche Advisory was published on January 9, 2007:

January 9, 2007 at 1:00 am

Forecast Discussion:

This advisory was posted on Tuesday, January 9, 2007 at 6:55 am

One last day of warm air temperatures today before a major cooling trend begins, likely leading to the coldest air temperatures so far this winter. Air temperatures at the upper elevations are already warming this morning with above freezing temperatures observed above 7,500'. Cold air is pooled in the mountain valleys this morning, but will warm as the day progresses. Ridgetop winds shifted around to westsouthwesterly overnight and will continue at light to moderate speeds today before becoming strong on Wednesday. A chance of snowfall exists from a low moisture system that is expected to enter the forecast area on Wednesday.

Warmer overnight air temperatures last night limited conditions for continued surface hoar growth on northerly aspects in the 6,800' to 8,000' elevation range. In this area, surface hoar up to 12mm (1/2 inch) has been widespread in wind protected areas for the past few days, escaping destruction from warm daytime air temperatures and winds. Low sun angles creating lots of shade and cool snow surface temperatures will give a chance for surface hoar to persist and become buried under a couple inches of snow tomorrow night. If this scenario plays out, we will likely see a persistent weak layer form in our snowpack. Get out and observe your favorite travel areas, taking note of any locations where surface hoar exists and its distribution. Any surface hoar crystals that become buried by the next snowfall will contribute to future snowpack instability.

Melt-freeze crusts continued to form on SE-S-SW aspects up to around 8,700' yesterday. Colder, unconsolidated snow lingers on wind protected northerly aspects below treeline. Stable hard slab conditions exist above treeline on all aspects.

Avalanche danger remains LOW for all elevations and aspects.

Brandon Schwartz, Avalanche Forecaster

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Today's Central Sierra Weather Observations:
0600 temperature at Sierra Crest (8,700 feet): 35 deg. F
Max. temperature at Sierra Crest past 24 hours: 37 - 45 deg. F
Average wind direction at Sierra Crest past 24 hours: easterly shifting to westsouthwesterly overnight
Average wind speed at Sierra Crest past 24 hours: 24 mph
Maximum wind gust at Sierra Crest past 24 hours: 49 mph
New snow fall at 8,200 feet past 24 hours: 0 inches
Total snow depth at 8,200 feet: 40 inches

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Mountain Weather Forecast For Today:
Mostly sunny skies
Temperature forecast for 8,000 to 9,000 feet: 38 - 48 degrees F.
Ridgetop winds forecast for the Sierra Crest: Westsouthwesterly 15 - 30 mph, G 45 mph
Snowfall expected in the next 24 hours: 0 inches

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2 Day Mountain Weather Forecast:
7000 to 8000 Feet
For today, mostly sunny skies. Day time highs 40 to 50 degrees F. Southwest winds 10 to 20 mph. Overnight, partly cloudy with lows 22 to 32 degrees F. West winds at 15 to 25 mph, gusting to 35 mph. Wednesday will be mostly cloudy with a slight chance of snow showers. Daytime highs 28 to 38 degrees F. Southwest winds at 30 to 40 mph, gusting to 60 mph are expected.

Above 8000 Feet
For today, mostly sunny skies. Daytime highs 38 to 48 degrees F. Westsouthwesterly winds at 15 to 30 mph, gusting to 45 mph. Overnight, partly cloudy with lows 25 to 35 degrees F. West winds at 20 to 30 mph, gusting to 50 mph. Wednesday will be mostly cloudy with a slight chance of snow showers. Daytime highs 26 to 36 degrees F. Southwest winds at 50 to 70 mph, gusting to 100 mph are expected.


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:
  Tuesday: Tuesday Night: Wednesday:
Weather:
Temperatures: deg. F. deg. F. deg. F.
Wind direction:
Wind speed:
Expected snowfall: O in. O in. O in.

For 8000-9000 ft:
  Tuesday: Tuesday Night: Wednesday:
Weather:
Temperatures: deg. F. deg. F. deg. F.
Wind direction:
Wind speed:
Expected snowfall: O in. O in. O in.