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

Jan 22nd, 2017–Jan 23rd, 2017

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

Regions

Mt Hood.

Watch for new wind slabs formed Sunday on exposed lee slopes, especially near and above treeline. Storm slabs should continue to slowly stabilize Monday. Watch for wet snow avalanches on steep solar aspects if the sun comes out in the afternoon.

Detailed Forecast

Mostly cloudy early Monday with a chance of a few light snow showers, light winds with cool temperatures. Clouds should decrease becoming partly cloudy late Monday.

These conditions should allow for a gradual decrease in avalanche danger as recent wind and storm slabs begin to settle and stabilize. 

Allow existing storm and recent wind slabs time to continue stabilizing on Monday. Watch for recent wind effects near and below ridgelines and avoid steep slopes with obvious signs of recent wind loading.  

Storm slabs should become more stubborn to trigger Monday. Watch for denser snow overlying weaker storm snow and stick to lower angled slopes. 

Snowpack Discussion

Weather and Snowpack

An arctic air mass was over the Northwest with fair, cold weather last week. Surface hoar and near surface faceted crystals formed in wind and sun-sheltered areas during this period. Observations over the next few days should help to determine what extent any of these weak persistent grain types might have survived the atmospheric river event and remain relevant to the forecast moving forward.

An atmospheric river moved over the Northwest Tuesday and Wednesday. Heavy rain was seen up to about 7000 feet at Mt. Hood. 3 day precipitation totals through noon Thursday were about 1.5 - 2 inches of water at the Meadows and Timberline stations. Light snow showers and cooler temperatures were seen Thursday. A frontal band rotating up from the south dropped about 6 inches of snow at Meadows and Timberline through 6 pm Friday with steady snow levels seen during the day.

Bands of showers moved across the Mt Hood area midday Saturday and again early Sunday, depositing 6-10 inches new snow with moderate winds. 

Recent Observations

The Mt Hood Meadows pro-patrol on Wednesday reported that rain penetrated about 10 inches into the snow with no results during avalanche control using explosives. Visibility was low on Wednesday, and it could not be determined if there had been any natural avalanches on the upper mountain.

Visibility remained poor on Thursday, but Meadows pro-patrol reported wind slabs releasing on NE aspects well above treeline control work with explosives. Wind slabs became less reactive near tree-line and no avalanche activity or layers or concern was reported below treeline.

By Saturday, patrol at Meadows were seeing very limited results as much of the recent wind slab problem had begun settling. At elevations below the recent wind loading, storm snow lacked cohesion and was providing nice conditions.  

No observations were received Sunday, to assess the storm or wind slab distribution and sensitivity of the recent 6-10 inches of storm 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.