Observation: NWAC Observer

All Observations

Basic Information

Observation Date:

March 26, 2023

Submitted:

March 26, 2023

Observer:

NWAC Observer - Keeley Rideout

Zone or Region:

West South

Location:

St. Helens (2500-5000ft, All Aspects)

Recent Avalanches?

Yes

Cracking?

None Experienced

Collapsing?

None Experienced

Sticky snow in trees. Lots of heavy snow coating trees.

Windy conditions as the sun breaks through NTL/ATL.

Hard to see point releases on steep slope below trees.

Wind affected surface near pit location.

Pit @4100ft on SE aspect. 28 degree slope. Air Temp: 35F. CT failures denoted by purple layers.

CT17 @30cm on density difference in new snow.

Advanced Information

Cloud Cover:

Overcast

Temperature:

35°F

Wind:

Light , SW

New/Recent Snowfall:

HST: 58cm

Today was overcast with steady snowfall most of the day, though the sun broke through every once in a while. Light winds gusting to moderate. ~2 cm of new snow accumulated over the course of the day and getting blown around, especially at elevations NTL/ATL. Returning climbers turned around at upper elevations after encountering white out conditions and strong winds.

Avalanche Observation Comments:

Some point releases were present on steep slopes below cliff bands/trees.

Below treeline the biggest hazard is tree bombs. There's a lot of snow glommed onto the trees and when the wind jostles it loose watch out! Warm sticky snow all through the trees and on the near treeline boundary made for tough skinning conditions (it's skinwax season).

Near and above treeline, light winds gusting to moderate kept snow swirling this afternoon - lots of wind features on ridgelines and on the snow surface. A widespread wind affected layer below a few centimeters of new snow made for 'interesting' skiing conditions.

A pit profile on a SE slope at 4100ft showed ~58cm of relatively dry new snow from this storm atop old wet snow. The total snow depth was deeper than my probe length (300cm). The surface was a wind crust ~3cm thick, 43cm down was another wind crust followed by a layer of graupel from the beginning of the storm atop the old snow.

A compression test got results in multiple layers of the new snow. The wind slab to failed immediately: CT1 @3cm with a planar fracture that slid easily. After that a density difference in the snow failed on CT17 @30cm with another planar fracture. CT25 failed on the old wind crust from early in the storm @43cm. Finally at CT30 the remaining snow failed on the graupel layer-old snow interface at 50cm down.

Problem	Location	Distribution	Sensitivity	Size	Comments
Wind Slab	N E S W	Isolated Specific Widespread	Unreactive Stubborn Reactive Touchy	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5	Comments: Failure @CT1
Wet Loose	N E S W	Isolated Specific Widespread	Unknown	D1 D1.5 D2 D2.5 D3 D3.5 D4 D4.5 D5	Comments: Lower elevations, especially on S/SE/E aspects

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