Backcountry Avalanche Forecast
East slopes WA Cascades - south of White 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
| Friday | Saturday | Sunday | ||||||
| 6am-Noon | Noon-6pm | 6am-Noon | Noon-6pm | 6am-Noon | Noon-6pm | |||
| Danger Trend | Slightly Increasing | Slightly Decreasing | Level | Slightly Decreasing | Level | Slightly Increasing | ||
| 7000' | 4 | 4 | 3 | 3 | 3 | 3 | ||
| 6000' | 4 | 4 | 3 | 3 | 3 | 3 | ||
| 5000' | 3 | 3 | 3 | 2 | 2 | 3 | ||
| 4000' | 3 | 3 | 2 | 2 | 2 | 2 | ||
| 3000' | 3 | 3 | 2 | 2 | 2 | 2 | ||
| 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
Friday and Friday night: High avalanche danger above 5 to 6000 feet and considerable below Friday morning, gradually decreasing Friday afternoon and night and becoming considerable above 4 to 5000 feet and moderate below.
Saturday and Saturday night: Slowly decreasing avalanche danger becoming considerable above 6000 feet and moderate below
Sunday and Sunday night: Slightly increasing avalanche danger mid-day through Sunday night, especially higher elevation lee slopes and sun exposed terrain
Snowpack Analysis
Gradually increasing amounts of wind driven snow at gradually rising freezing levels were deposited over a variety of buried weak layers Thursday into Friday morning. These weak layers included low density snow, spotty surface hoar, and a slightly faceting old crust, with a poor bond developing between the newly arriving snow and any of the old snow surfaces or existing weak layers. This produced a significant danger increase as slowly thickening and increasingly sensitive wind slabs gradually spread to progresively lower elevations, especially on northwest through northeast exposures. Avalanche control results from early Friday at Mission Ridge Ski Area indicated pretty good results along with good fracture propagation, shooting cracks and remote triggering of a 3 ft slab which was described as "spooky".
While field reports indicate that the most recent surface hoar growth was spotty and confined to shady pockets on northwest through northeast exposure slopes at mid and higher elevations, some larger and generally weaker surface hoar layers that developed in early-mid February may still exist beneath 1 to 2 feet or more of recent snow. Most expected avalanching should involve only the most recently received new snow releasing on one of the aforementioned weak layers and this should produce slabs ranging from about 6 to 18 inches; however, some slab releases or cornice falls may trigger isolated larger releases to one of these older surface hoar layers that have been a problem since their development over a month ago. These larger slab depths may reach 2 to 3 feet or more, entrain most of the recent snow, and run relatively long distances.
Detailed Forecasts
Friday and Friday night
Increasing moderate rain or snow spreading into most areas Friday morning was accompanied by strong winds and slight cooling. This maintained or slightly increased the considerable to high avalanche danger along the Cascade east slopes. Along with sensitive cornices that could easily fail through human triggers and a strong probability of thickening slabs of up to 1 to 3 feet releasing on buried weaknesses in more heavily wind loaded terrain, back country travel in avalanche terrain is not recommended Friday morning and mid-day.
It should also be noted that owing to the recent and current strong winds, a relatively stable and wind scoured/hardened snowpack may exist on wind exposed terrain immediately adjacent to very unstable slabs on lee terrain. Also, some paths may have significant wind pillows developing much lower than normal due to the strong winds, with the result that fracture initiation may start lower than normal in some slide paths.
Moderate snow should decrease and become more showery Friday afternoon with light to occasionally moderate showers slightly increasing late Friday night. While rapidly lowering freezing levels are expected, moderate to strong winds should only very slowly decrease overnight. Although this should allow for a slow decrease in the danger, mainly at lower and mid elevations, careful snowpack evaluation, cautious routefinding and conservative decsion making should remain essential in order to avoid avalanche involvement.
Saturday and Saturday night
Light to moderate showers Saturday morning should further decrease mid-day and become scattered Saturday afternoon. Along with decreasing winds and continued low freezing levels, associated slow settlement of recently thickening wind slabs should combine with decreasing load to allow for a slow decrease in the danger in most locations, especially at lower elevations where some previously wet surface snow may have formed a weak crust. However, expected cold temperatures and some residual wind transport should limit settlement and related danger decrease on lee slopes near higher ridgelines...mainly north, northeast and east exposures above about 5 to 6000 feet. Also, a local slight danger increase is possible on slopes receiving sun breaks Saturday afternoon. As a result, continued careful snowpack evaluation and cautious routefinding are urged, and conservative decision making is still strongly encouraged on slopes not experiencing stabilization through recent avalanche releases.
Although some increase in mid and high clouds is likely Saturday night, low freezing levels and relatively light winds should allow for futher slow settlement and stabilization of recent slabs overnight.
Outlook Sunday
A moderate to strong front should stall and slowly weaken along the Washington coast on Sunday. Several impulses on this front should intermittently nudge the front eastward. This should result in periods of occasional light rain or snow in the Olympics and northern Cascades and considerable mid and high cloudiness further south (in the central and southern Cascades). Along with rising freezing levels, this weather should produce a gradual increase in the avalanche danger…especially on previously wind loaded terrain at higher elevations, and on slopes receiving filtered sunshine in the south and central Cascades. Increasing loose or isolated slab slide activity may be possible as a result of either warming or sunshine effects.
As the front nudges further eastward Sunday night, associated increasing ridgetop winds may begin to reload lee slopes...mostly northeast through northwest exposures...at higher elevations.
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.