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 4th, 2016–Jan 5th, 2016

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

Regions

Mt Hood.

Wind slab will need to watched for on on Tuesday a variety of aspects. New shallow storm slab will also be possible on Tuesday.

Detailed Forecast

A couple more weak short waves and weak bands of precipitation should move out of a large weak trough and over the Northwest on Tuesday. Several inches of snowfall is possible at Mt Hood.

Wind slab will need to watched for on a variety of aspects. Old wind slab may still be found on the more usual north to southeast slopes.  Wind slab from over the weekend is more likely on west aspects.

New shallow storm slab will also be possible on Tuesday. Warming of more than a few degrees would help make new snowfall somewhat upside down with denser snow near the surface which contributes to instability.

Snowpack Discussion

Fair weather was seen the last couple days of December through the weekend. This weather caused lots of consolidation and stabilizing of the heavy snow from December. By Thursday through Saturday, moderate to strong east-northeast winds had significantly scoured or transported available surface snow onto lee westerly  aspects, mainly in the near and above treeline elevation bands.

NWAC observer Laura Green was in the Newton Creek drainage Friday and found good skiing in non-wind affected terrain. Even on wind loaded slopes near treeline, the denser wind slab was bonding to underlying snow and no natural or skier triggered avalanches were noted. Significant wind loading continued to occur on the upper mountain Friday and to lesser extent Saturday.

Surface snow sculpted by wind and active wind transport. Photo: Laura Green

By Monday morning the Mt Hood Meadows pro patrol reported warming and a widespread 1 cm freezing rain crust up to 7000 feet. This layer was not reactive to tests and should not create a new avalanche danger and will give poor ski conditions.

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.