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 13th, 2016–Jan 14th, 2016

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

Regions

Mt Hood.

The avalanche danger should gradually increase through the day Thursday as new storm snow is deposited and wind slabs begin forming on the lee, higher elevation terrain. Cautious route-finding and terrain selection will be essential Thursday at higher elevations near or above treeline to stay safe and avoid storm related avalanche problems. 

Detailed Forecast

The next in a series of frontal systems should arrive during the day Thursday, causing increasing light to moderate snow and winds, at relatively cool temperatures.  

New shallow storm or wind slabs may form by late Thursday, causing a gradual increase in danger.  Cautious route-finding and terrain selection will be essential on Thursday, especially above tree line. 

Particular caution should be used on steeper terrain, giving additional storm instabilities time to settle. Look for wind slab on a variety of aspects near and above treeline due to shifting winds. Watch for signs of firmer wind transported snow that can indicate wind slab layers near and below ridges.

Snowpack Discussion

Fair weather was centered around the New Year, allowing the heavy snow that fell prior to Christmas to settle and stabilize. Moderate to strong east-northeast winds in early January had significantly scoured most of the available surface snow in the near and above treeline elevation bands.

Warming associated with the storm Tuesday and early Wednesday caused rain or mixed rain and snow to near tree line by early Wednesday before cooling dropped the snow levels by later Wednesday. Strong winds above treeline and water equivalents of nearly 2 inches have formed extensive hard slab conditions on lee slopes above treeline. Howitzer control results Wednesday produced hard slab avalanches on lee slopes well above treeline above Mt Hood Meadows, though human triggering a similar slide is unlikely. 

 Near and below treeline, more shallow and isolated pockets of wind slab produced smaller slides with explosives, mostly 8 inches.

Cooling through the day Wednesday has allowed for previously wet surface snow to begin forming crusts, while allowing storm or wind slabs to gradually stabilize.

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.