Dashboard Regions Weather Stations Radar Alerts Glossary
Contact About
Log In

Register for an account and never miss a forecast again!

Register

Avalanche Forecast

Archived

Feb 25th, 2018–Feb 26th, 2018

Alpine
Natural avalanches possible, human triggered probable.
Treeline
Natural avalanches possible, human triggered probable.
Below Treeline
Natural avalanches possible, human triggered probable.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely, human triggered possible.

Regions

Mt Hood.

Intense snow and wind brought dangerous avalanche conditions and very large Wind Slabs avalanches to the Mt Hood area. Three feet of snow has accumulated since Friday. Avoid obvious wind drifts and deep pillows of snow on leeward and crossloaded slopes 35 degrees and steeper.

Detailed Forecast

Dangerous avalanche conditions will persist Monday following a strong storm passage Sunday. Snow showers should taper overnight Sunday and end by early Monday. Temperatures should cool with diminishing winds by Monday. Monday should be cool with light winds and partial clearing with a chance of a few light snow showers but little if any accumulation expected. 

The strong storm Sunday produced widespread wind and storm slabs in the Mt Hood area. These large wind and storm slabs will take some extra time to heal and strengthen.

You will be able to trigger an avalanche Monday, especially in areas that received significant wind loaded snow, such as steep slopes below ridges, mainly facing North to Southeast. Any triggered avalanche could become very large as there is a significant amount of storm snow available to become involved in an avalanche.

Back country travelers should continue to travel with extra caution and best to travel in shallower angled terrain well away from avalanche paths or runout zones where avalanches release from above. 

Snowpack Discussion

Older low density snow from last week has been loaded by back to back strong storms over the weekend with about 3 ft of new storm snow accumulating by Sunday evening! 

Very strong winds and heavy snowfall intensities since late Friday have built large to very large wind slabs near and above treeline. Storm slabs have built over weaker lower density snow deposited late last week. 

This snowpack structure is creating dangerous avalanche conditions in the Mt Hood area. 

Avalanches releasing in the most recent storm snow may step down to older storm layers creating large avalanches.

The deepening storm snow now sits over a strong crust layer formed and buried on Saturday 2/17. This crust has been reported up to 6600 feet by professionals in the region. 

One person was killed in an avalanche south of Snoqualmie Pass on Sunday. Our condolences go to the friends and family of the victim. If conditions allow, NWAC staff will visit the accident site.

Observations

By Sunday morning, MHM professional patrol reported "monumental" snow drifts! These conditions have only become larger by Monday.

MHM professional patrol on Saturday reported white out conditions above treeline with significant wind transport occurring. Below treeline the surface snow was forming unstable storm slabs. Still relatively shallow storm slab avalanches were releasing with explosives Saturday morning. 

NWAC pro-observer Laura Green traveled in the Mt Hood backcountry Friday. Laura reported stable conditions prior to Friday’s incoming storm. She found a right-side-up snowpack with loose unconsolidated surface snow.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.