Backcountry Avalanche Forecast
East slopes WA Cascades - north of Stevens Pass
The NWAC program is administered by the USDA-Forest Service and operates out of the National Weather Service Forecast Office in Seattle. NWAC services are made possible by important collaboration and support from a variety of federal, state and private cooperators.
Weather Service ID WAZ513-518-519-019-042-501-502-ORZ011
| Wednesday | Thursday | |||||||
| 6am-Noon | Noon-6pm | 6am-Noon | Noon-6pm | |||||
| Danger Trend | Level | Slightly Decreasing | Strongly Increasing | Strongly Increasing | ||||
| 7000' | 2 | 2 | 3 | 3 | ||||
| 6000' | 2 | 2 | 3 | 3 | ||||
| 5000' | 2 | 2 | 3 | 3 | ||||
| 4000' | 1 | 1 | 3 | 3 | ||||
| 3000' | 1 | 1 | 3 | 3 | ||||
| Notes: This represents a regional scale avalanche forecast for each elevation and time period shown. For complete information see the detailed avalanche forecast. | ||||||||
Jump to Danger Scale Legend at bottom of forecast
Forecast
Wednesday and Wednesday night: Moderate avalanche danger above 5000 feet and low below. Avalanche danger gradually increasing Wednesday night.
Thursday and Thursday night: Increasing considerable avalanche danger below 7000 feet Thursday. Further increasing high avalanche danger above 5000 feet and considerable below Thursday night.
Snowpack Analysis
Weak frontal passages Sunday night and again Tuesday night have deposited generally shallow amounts of low density unconsolidated snow amounting to total new snow of about 4 to 6 inches. The new snow has fallen on and is weakly bonded to generally hard melt-freeze crust surfaces or settled old snow on shaded slopes. The new snow may have also buried a hoar frost layer that formed during clearing periods last weekend. The new snow in most areas is unconsolidated and therefore lacks the cohesion and ability to propagate a fracture and therefore fail as a slab avalanche.
There may be a few isolated unstable slab layers but these should be confined to mainly higher elevations near ridges where shallow triggered avalanches could be possible.
While the current danger may not be too great, the current snow pack structure is such that it should quickly become unstable when loaded with heavy snowfall along with strong winds such is expected beginning early Thursday, continuing through Thursday.
Backcountry travelers should be alerted to the expected significant increase in danger over the next few days.
There remains some older buried hoar frost layers from early and mid-late February on some sheltered north aspects, especially in the northeast Washington Cascades that remain a concern. This layer has been settling somewhat over the past few weeks, but guides in the area continue to uncover the layer in test pits where relatively easy and clean shears persist down about 15 to 20 inches. This layer caused some natural and triggered slab avalanches as late as about a week ago.
Detailed Forecasts
Wednesday and Wednesday night
Light snow showers will end by midday, giving way to some sunshine along with high clouds and light winds. This should allow for a slow decrease in danger, mainly later Wednesday as isolated unstable layers settle. Any sunshine received during the afternoon could make wet snow avalanches possible on steeper south facing slopes where extra caution is advised.
Increasing strong winds Wednesday night with increasing light snow overnight should lead to a gradually increasing danger. New unstable layers will form over weak existing surface snow.
Thursday and Thursday night
Very strong winds and moderate to heavy snow along with a slight warming trend is expected Thursday. This should cause a further increase in danger in all areas, especially higher elevations where strongest winds are expected. New increasingly dense and deep unstable layers should form, especially on lee slopes at higher elevations where natural or triggered slab avalanches will be likely. Backcountry travel on steep open slopes at higher elevations is not recommended Thursday.
Further warming and moderate snow and very strong winds Thursday night should lead to a further increasing danger.
n/a
Danger Scale Legend
| 5 | = Extreme avalanche danger | |
| 4 | = High avalanche danger | |
| 3 | = Considerable avalanche danger | |
| 2 | = Moderate avalanche danger | |
| 1 | = Low avalanche danger | |
Warning = Extreme or high avalanche danger occurring or expected to occur within 12 hours: at or below 4000 feet in the Olympics and/or WA Cascades; at or below 5000 feet in the Mt. Hood Area.
Watch = Warning conditions expected within 12-48 hours.
Special Conditions = Unusual conditions meriting special attention that do not meet Watch or Warning criteria.
Click here for complete definitions of the avalanche danger scale.
Backcountry travelers should be aware that elevation and geographic distinctions are approximate and that a transition zone between dangers exists. Remember there are avalanche safe areas in the mountains during all levels of avalanche danger. Contact local authorities in your area of interest for further information.
NWAC weather data and forecasts are also available by calling 206-526-6677 for Washington, 503-808-2400 for the Mt Hood area, or by visiting our Web site at www.nwac.us. Remember that these avalanche forecasts apply to back country avalanche terrain below 7000 feet outside of developed and operating ski areas or highways.
The NWAC program is administered by the USDA-Forest Service. NWAC forecasts, data and avalanche or mountain weather information are made possible by partnerships between the Forest Service and many important cooperators, including the National Weather Service, Washington State Department of Transportation, Washington State Parks and Recreation Commission, Washington Snowparks and Snowmobile Grants, National Park Service, Ski Washington, Pacific Northwest Ski Area Association, the Friends of the Avalanche Center and others.
This forecast is prepared for cooperators and users of the NWAC, as an aide to tranportation and recreational operations, and to help promote public safety in the NW mountains.