Backcountry Avalanche Forecast Central Sierra Nevada
Sierra Avalanche Center
www.sierraavalanchecenter.org
- Issued
- Monday, December 11, 2023 - 6:52AM
- Expires
- Tuesday, December 12, 2023 - 6:52AM
- Author
- Steve Reynaud
The Bottom Line
Old, weak, sugary, snow continues to exist near the base of the snowpack below the most recent storm snow. Avalanches will remain possible where strong snow exists above this weak snowpack. Increased consequences continue to exist of any avalanche involvement due to the rocky and shallow snowpack.
Avalanche Danger
Monday, December 11, 2023
Tuesday, December 12, 2023
- Above Treeline2 - Moderate
- Near Treeline2 - Moderate
- Below Treeline2 - Moderate
 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: Persistent Slab
Problem Type
Aspect/Elevation
Likelihood
Size
While skinning up this slope near an N-facing area at 9800 ft on Tamarack Peak, the group remotely triggered shooting cracks and a collapse that sounded like "thunder."
Old faceted weak snow exists on most NW-N-NE aspects below the most recent storm snow. The exact structure and weakness of the snowpack varies widely by location and elevation. Areas with wind blown snow or consolidated recent storm snow, could provide all the ingredients for a persistent slab avalanche to occur. Previous wind scouring may have left some of the weakest snow in locations for mid or lower on the slope avalanches to occur. If a persistent slab avalanche did occur, it could break wider than expected and could be remotely triggered.
Any signs of instability like recent avalanches, shooting cracks, whumpfing sounds, or snowpack collapses would indicate an unstable snowpack in your area. Use low-angle, non-avalanche terrain not connected to steeper areas above or beside it if you see signs of instability. If an avalanche did occur, it could result in serious trauma from all the exposed rocks and current shallow snowpack.
Forecast Discussion
A weak faceted (sugary) snowpack exists above about 8,000', but could be encountered as low as 7,200' in isolated locations. As elevation increases expect to find layers of faceted snow in between rain crusts. Above about 8,500' or so, rain crusts disappear and the snowpack becomes nearly all weak faceted snow. Generally speaking, the higher up you go on wind protected NW-N-NE aspects, the weaker the snowpack. Early season NE wind events previously scoured some exposed slopes down to dirt, rock, or ice. This makes the distribution and location of the weak faceted snow more variable through the forecast region.
There is still the potential to hit many obstacles (rocks, logs, open water, bushes, etc.) that are barely covered (or not) by the shallow snowpack. Areas with a supportable mid snowpack rain crust in the 7,500’ to 8,500’ elevation range provide the most usable snowpack. Anticipate encountering a different snowpack structure and a different set of travel conditions if you are moving from one place to another around the forecast area.
Media
Mountain Weather
- Issued
- Monday, December 11, 2023 - 6:38AM
- Author
- Steve Reynaud
High pressure will continue to provide dry conditions, valley inversions, and near average temperatures. Increasing cloud cover will move into the area today. Quiet weather is expected throughout the week with some colder temperatures and increasing winds expected midweek.
| 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 | Increasing clouds. | Partly cloudy then becoming mostly cloudy. Snow levels 6000 to 6500 feet. Chance of precipitation is 0%. | Partly cloudy then becoming clear. Snow levels 5500 to 6500 feet. Chance of precipitation is 0%. | Sunny. Snow levels 5500 feet. Chance of precipitation is 0%. |
| Temperatures 7000 to 8000 ft. | @ 5am: 24 to 40° F | Max: 43 to 53° F | 44 to 50. ° F | 20 to 26. ° F | 33 to 38. ° F |
| Temperatures 8000 to 9000 ft. | @ 5am: 28 to 43° F | Max: 45 to 54° F | 40 to 46. ° F | 18 to 23. ° F | 29 to 35. ° F |
| Mid Slope Winds | Light winds. | Light winds. | Light winds. | Light winds becoming east around 15 mph with gusts to 25 mph in the afternoon. |
| Ridgetop Winds | Southwest 15 to 20mph with gusts up to 38mph. | Southwest 15 to 25 mph. Gusts up to 35 mph. | Light winds. | Light winds becoming east around 15 mph with gusts to 30 mph in the afternoon. |
| Snowfall 7000 to 8000 ft. | 0 | No accumulation. | SWE = None. | No accumulation. | SWE = None. | No accumulation. | SWE = None. |
| Snowfall 8000 to 9000 ft. | 0 | No accumulation. | SWE = None. | No accumulation. | SWE = None. | No accumulation. | SWE = None. |
| Total Snow Depth between 8200 and 8700 ft. | 8 to 23 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.