Backcountry Avalanche Forecast Central Sierra Nevada
Sierra Avalanche Center
www.sierraavalanchecenter.org
- Issued
- Tuesday, December 5, 2023 - 6:53AM
- Expires
- Wednesday, December 6, 2023 - 6:53AM
- Author
- Steve Reynaud
The Bottom Line
A weak snowpack continues to exist throughout much of the forecast region. There are limited areas where a strong slab layer exists on top of this weak snowpack. Avalanche conditions are isolated to these areas where strong snow exists on top of weaker snow until our next storm arrives. Limited snow coverage is available for over the snow recreation with early season conditions present.
Avalanche Danger
Tuesday, December 5, 2023
Wednesday, December 6, 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
Weak faceted snow that formed earlier in the season can be found near the ground of our shallow snowpack on NW-N-NE aspects. This weak snow is mixed in with rain crusts near 8000', with mostly faceted snow and depth hoar existing above 9000'. Long clear nights and low sun angles continue to promote the faceting process on these shaded slopes. Recent storm snow over this past weekend added load to these weak layers and formed overlying stronger slabs of snow in some areas. These weak layers are highly variable in distribution and strength. There is a high level of uncertainty predicting exactly where or if persistent slab avalanches may occur and how much additional load will be required.
Any snowpack collapses, whumpfing sounds, or shooting cracks represent signs of unstable snow. If you encounter any of these signs of instability, avoid NW-N-NE aspect avalanche terrain in the area.
Forecast Discussion
1 to 2 feet of snow can be found on NW-N-NE aspects above 8000' throughout the forecast region. Continuous snow cover starts around 7,200' to 8,000' along the Sierra Crest and 8000’ to 8500’ in the Carson Range. There is a lot of variability in the structure of the existing snowpack depending on elevation and location with concerning weak layers in some areas on NW-N-NE aspects. Some locations are thick rain crust either with or without a thin layer of facets. Some locations are a mix of layers of rain crusts and faceted snow. While other areas are all faceted snow and depth hoar without any crusts. There is generally little to no rain crust within the snowpack above 8,800' to 9,000'.
Previous NE wind events scoured the upper portion of many wind exposed slopes down to rock, dirt, and/or ice before the recent snowfall. Despite this scouring, weaker faceted snow persisted on the lower portions of many slopes. A much thinner snowpack or bare ground exists across E-SE-S-SW-W aspects.
While the snowpack has become more usable for over the snow travel, there is still the potential to hit many obstacles (rocks, logs, etc.) that are barely covered. Areas with a supportable rain crust below the recent new snow are the most usable. If you are traveling on snow for recreation, you should come up with a daily travel plan based on the current conditions and associated hazards. 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
- Tuesday, December 5, 2023 - 6:30AM
- Author
- Steve Reynaud
Light winds, dry conditions, and mild temperatures will continue for our region today. A couple small storms are expected Wednesday afternoon into Thursday. Winds will increase on Wednesday with ridgetop winds forecasted at 80-90mph and peak gusts well over 100mph. These small storms will have the possibility of bringing a few inches to the Tahoe Basin and up to 6'' along the Northern Sierra Crest by the end of Thursday. High pressure with dryer weather is expected for the weekend.
| 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 | Sunny and clear. | Sunny. Snow levels 9000 feet. Chance of precipitation is 0%. | Partly cloudy. Snow levels 8500 feet. Chance of precipitation is 0%. | Partly cloudy then becoming mostly cloudy. Snow likely in the afternoon. Snow levels 7500 feet. Chance of precipitation is 70%. |
| Temperatures 7000 to 8000 ft. | @ 5am: 22 to 46° F | Max: 41 to 54° F | 49 to 54. ° F | 31 to 37. ° F | 41 to 46. ° F |
| Temperatures 8000 to 9000 ft. | @ 5am: 31 to 43° F | Max: 40 to 51° F | 45 to 51. ° F | 29 to 34. ° F | 36 to 42. ° F |
| Mid Slope Winds | South 5 to 10mph with gusts to 15mph. | Light winds. | Southwest 15 to 20 mph. Gusts up to 45 mph after midnight. | Southwest 15 to 30 mph increasing to 25 to 35 mph in the afternoon. Gusts up to 70 mph. |
| Ridgetop Winds | SW 15 to 20mph with gusts to 25mph. | Light winds becoming southwest around 15 mph with gusts to 30 mph in the afternoon. | Southwest 15 to 25 mph with gusts to 40 mph increasing to 25 to 35 mph with gusts to 60 mph after midnight. | Southwest 30 to 45 mph with gusts to 80 mph increasing to 45 to 60 mph with gusts to 100 mph in the afternoon. |
| Snowfall 7000 to 8000 ft. | 0 | No accumulation. | SWE = None. | No accumulation. | SWE = None. | 70% probability up to 2 inches. | SWE = Up to 0.40 inch. |
| Snowfall 8000 to 9000 ft. | 0 | No accumulation. | SWE = None. | No accumulation. | SWE = None. | 70% probability of 1 to 3 inches. | SWE = Up to 0.35 inch. |
| Total Snow Depth between 8200 and 8700 ft. | 12 to 13 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.