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 23rd, 2016–Feb 24th, 2016

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

Wind slab may be touchy on recently loaded aspects Wednesday. Depending on how much sunshine is received, loose wet avalanches may also become a problem on steeper solar slopes on Mt. Hood. 

Detailed Forecast

Cool easterly flow should abate on Wednesday with warming temperatures forecast across the west slopes and Mt. Hood. However, a dissipating frontal band will push mid and high clouds over the area, potentially limiting sun effects on Wednesday. 

Recent E-SE winds have redistributed recent snowfall to non-traditional westerly aspects forming generally shallow but touchy windslab primarily in the near and above treeline elevation bands, but may still be possible below treeline depending on local loading patterns.  

Watch for wind transported snow on a variety of aspects Wednesday: Don't let the combination of Moderate avalanche danger with non-traditional lee aspects/cross-loaded slopes catch you by surprise!  

Loose wet avalanches may be the primary problem in your area depending on the amount of sunshine Wednesday. Freezing levels will rise on Wednesday and combined with sunshine should activate loose wet avalanches on steeper solar slopes. Watch for pinwheeling and rollerballs as precursors to more significant loose wet activity and especially be wary of loose wet avalanches around terrain traps. 

Snowpack Discussion

Weather and Snowpack

Last week, heavy rain and mild temperatures dominated along the west slopes including Mt. Hood forming the latest rain crust. NWAC sites at Mt Hood recorded about 2.5 inches of rain over the 2 days ending Tuesday morning February 16th.

An active and cooler pattern began to bury the crust on February 17th and dropped about 2 feet of snow at Mt Hood stations from Wednesday through Saturday morning. A weak front on Sunday only brought a few inches of additional snowfall through Monday morning.

Storm layers in the snow received from Wednesday to Saturday have had many days to stabilize. Bonding of storm snow to the February 17th crust varied along the west slopes and Mt. Hood initially, but also should have improved over the last few days.

Moderate E-SE winds Monday night and Tuesday at Mt. Hood likely redistributed recent surface snow and built shallow but new wind slab in all elevation bands. 

The mid and lower snow pack along the west slopes should be a stable mix of crusts and layers of moist and rounded snow crystals.

Recent Observations

The Mt Hood Meadows pro-patrol reported large explosively triggered 2-3 foot hard wind slab on north to east slopes in the above tree line Saturday. In the near and below treeline storm snow was well bonded to the February 17th crust with some small easily triggered storm slab on isolated terrain features.

Several reports from the Mt. Hood pros on Monday indicated a generally stable snowpack with minimal sun affects on solar slopes and some scoured windward slopes above treeline due to the persistent westerly transport winds. Loading patterns were reversed on Tuesday, likely cross-loading some slopes.  

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.