Backcountry Avalanche Forecast Central Sierra Nevada
Sierra Avalanche Center
www.sierraavalanchecenter.org
- Issued
- Friday, December 1, 2023 - 6:49AM
- Expires
- Saturday, December 2, 2023 - 6:49AM
- Author
- Steve Reynaud
The Bottom Line
New snow accumulation over the last 24 hours along with strong winds have created slabs of wind blown snow. In some areas, these new wind slabs exist on top of a very weak snowpack. Avalanches are possible today. Limited terrain continues to exist for over the snow recreation.
Avalanche Danger
Friday, December 1, 2023
Saturday, December 2, 2023
- Above Treeline2 - Moderate
- Near Treeline2 - Moderate
- Below Treeline1 - Low
 1 - Low |  2 - Moderate |  3 - Considerable |  4 - High |  5 - Extreme | |
|---|---|---|---|---|---|
| Travel Advice | Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. | Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. | Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. | Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. | Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain. |
| Likelihood of Avalanches | Natural and human-triggered avalanches unlikely. | Natural avalanches unlikely; human-triggered avalanches possible. | Natural avalanches possible; human-triggered avalanches likely. | Natural avalanches likely; human-triggered avalanches very likely. | Natural and human-triggered avalanches certain. |
| Avalanche Size and Distribution | Small avalanches in isolated areas or extreme terrain. | Small avalanches in specific areas; or large avalanches in isolated areas. | Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. | Large avalanches in many areas; or very large avalanches in specific areas. | Very large avalanches in many areas. |
Avalanche Problems (1)
Problem #1: Wind Slab
Problem Type
Aspect/Elevation
Likelihood
Size
Recent new snow and strong SW-W winds have created wind slabs in near and above treeline areas. Most locations throughout the forecast area received 2 to 3'' of new snow overnight with small wind slabs expected for today. Areas that received the higher end snow totals, such as Carson Pass which received 6'' of new snow, larger wind slabs will be possible. This includes below treeline terrain. These larger formed wind slabs could cause failure deeper into the old weak snow near the ground. These avalanches would be larger and wider having increased consequences.
Look for blowing snow, new cornice formation, snow surface signs, and wind pillows as to where wind slabs may have formed. Any cracking, collapsing, or whumpfing sounds would be signs that you are overloading the weak layer below the new storm snow. Avalanches could occur in starting zones at the top of slopes, or potentially midslope where old weak snow exists. Very low snowpack conditions continue and even a small avalanche could have large consequences with all the obstacles present.
Forecast Discussion
Throughout the forecast region, 1 to 2 feet of snow can be found on NW-N-NE aspects above 8000'. The snowpack is made up of rain crusts and weak faceted snow. At elevations around 8000', mostly firm supportable rain crusts are present. At higher elevations above 8500', a very weak snowpack structure exists and is made up of facets and large depth hoar. Previous NE wind events have scoured many wind exposed slopes down to rock, dirt, and/or ice. Snow coverage and snowpack structure are highly variable throughout the forecast region.
Early season conditions exist with many obstacles (rocks, bushes, logs, open water, etc.) exposed or barely covered. Hitting one of these hazards could easily end your season before it even begins. If you are traveling on snow for recreation, you should come up with a daily plan based on the current conditions and carry your normal backcountry kit including avalanche rescue gear (avalanche transceiver, probe, shovel).
Media
Mountain Weather
- Issued
- Friday, December 1, 2023 - 6:38AM
- Author
- Steve Reynaud
Unsettled weather will continue through the weekend with periods of light snow and gusty winds. 1 to 6'' of snow fell during the last 24 hours mainly favoring the higher elevations of the southern part of the forecast area. Periods of light snow showers will continue into Sunday morning with minimal accumulation expected. Dryer and warmer conditions are expected starting early next week.
| Central Sierra Nevada | Conditions in the last 24hrs | Weather Forecast for Today Produced in partnership with the Reno NWS | Weather Forecast for Tonight Produced in partnership with the Reno NWS | Weather Forecast for Tomorrow Produced in partnership with the Reno NWS |
|---|---|---|---|---|
| Weather | Cloudy with snow. | Partly cloudy. Snow levels below 5500 feet. Chance of precipitation is 5%. | Mostly cloudy. Slight chance of snow showers in the evening. Snow levels 5500 feet. Chance of precipitation is 10%. | Mostly cloudy. Slight chance of snow showers. Snow levels 5500 feet. Chance of precipitation is 20%. |
| Temperatures 7000 to 8000 ft. | @ 5am: 18 to 28° F | Max: 26 to 37° F | 32 to 37. ° F | 19 to 25. ° F | 34 to 39° F |
| Temperatures 8000 to 9000 ft. | @ 5am: 15 to 25° F | Max: 23 to 34° F | 27 to 33. ° F | 17 to 22. ° F | 30 to 35 ° F |
| Mid Slope Winds | SW 5 to 10mph with gusts to 16mph. | Light winds becoming west around 15 mph with gusts to 30 mph in the afternoon. | West around 15 mph with gusts to 25 mph in the evening becoming light. | Southwest 15 to 20 mph. Gusts up to 35 mph in the afternoon. |
| Ridgetop Winds | SW 20 to 25mph with gusts to 35mph. | West 20 to 30 mph with gusts to 55 mph. | West 20 to 30 mph with gusts to 60 mph. | Southwest 20 to 30 mph increasing to 25 to 40 mph in the afternoon. Gusts up to 65 mph. |
| Snowfall 7000 to 8000 ft. | 1 to 4 inches | No accumulation. | SWE = none. | Up to 1 inch.. | SWE = less than .10 inch. | Up to 1 inch. | SWE = less than .10 inch. |
| Snowfall 8000 to 9000 ft. | 2 to 6 inches | No accumulation. | SWE = none. | Up to 1 inch. | SWE = less than .10 inch | Up to 1 inch. | SWE = less than .10 inch. |
| Total Snow Depth between 8200 and 8700 ft. | 8 to 12 inches |
This information is provided by the U.S.D.A. Forest Service and describes general backcountry avalanche hazard and conditions.
It does not apply to ski areas and highways where avalanche mitigation is conducted.