Avalanche Forecast

Archived

Dec 7th, 2015–Dec 8th, 2015

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Regions

Mt Hood.

Dangerous wet snow or reactive wet slab avalanches are expected near and above treeline Tuesday on Mt Hood.

Detailed Forecast

Another strong warm front is expected Tuesday. Strong southwest to west winds near ridges and increasing heavy to very heavy mostly rain at continued very high freezing levels is expected through the day Tuesday.

More loading or increasingly large storm or wind slab will continue to be the focus on Tuesday.

The warming and change from snow to rain Monday may have already caused a widespread natural avalanche cycle by the time Tuesday's storm arrives, however where still snowing this should reload new slab layers over the strong November crust.

With little snow near and below treeline at Mt Hood, wet loose snow avalanches will not be in the forecast. But change your plans if you find wet snow deeper than a few inches or see signs of wet loose activity such as pin wheels or natural wet loose avalanches.

Snowpack Discussion

Weather and Snowpack:

We had a wet and wild November with about 18-22 inches of water at NWAC station at Mt Hood only amounting to about 1-2 feet of snow above 6000 feet. This formed a strong crust in mid November.

In late November, strong high pressure and sunny weather persisted over Mt Hood.

The weather so far in December has become very active, with heavy snowfall at Mt Hood through early Monday, followed by very heavy rain to high elevations Monday afternoon. Timberline had 1 inch of rain in an hour's time this afternoon!.

Reports:

We don't have much information for Mt Hood yet this season.

The Mt Hood Meadows pro-patrol on Sunday found little on avalanche control. But on a northeast slope at 6600 feet a ski cut gave a sensitive 6-8 inch nearly fully path slab avalanche that released on the mid November crust.

Problems

Wet Slabs

Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.

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.