Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
April 5, 2023
Submitted:
April 5, 2023
Observer:
NWAC Forecaster - Joe Dellaporta
Zone or Region:
Mt Hood
Location:
Heather & Clark Canyons/ Pea Gravel

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
None Experienced
Collapsing? 
None Experienced

Media/Attachments

Accordian Bowl Avalanche HS-AE-Rd-D3-I Max crown depths:5 ft
Shallow parts of crown
Rollerballs on west aspects in Heather
hard slab debris
Smaller explosive triggered soft slabs in wind drifted snow.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Sunny
Temperature:
32°F
Wind:
Calm , W
New/Recent Snowfall:
<1 in

The sun felt warm today and made solar aspects below 7000' moist. However, after 1300 clouds started rolling in and ridgeline winds out of the W started increasing. On my ski out I noticed small rollers shedding off of steep west aspects.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Apr 4, 2023 7:00 am
() 		Heather Canyon
SE 6100ft 		D3
R4 		HS-Hard Slab I-New/Old Interface 3.5ft AE-Explosive Surface
c-Intentional
Very large (D3) hard slab avalanche triggered by a small explosive on an ESE near treeline. A 4" layer of lower-density precipitation particles observed at the interface of slab failure about 12" above the 3/31 crust.
Massive, blocky debris from a very large (D3) hard slab avalanche triggered by a small explosive on an ESE near treeline. Crown depth 2-6 ft. 
Very large (D3) hard slab avalanche triggered by a small explosive on an ESE near treeline. Crown depth 2-6 ft. 
Very large (D3) hard slab avalanche triggered by a small explosive on an ESE near treeline. Crown depth 2-6 ft.  Avalanche runout pictured. The debris descended Heather Canyon and re-ascended 100 ft up Pea Gravel Ridge.
Very large (D3) hard slab avalanche triggered by a small explosive on an ESE near treeline. Crown depth 2-6 ft. 
View from the top of the convex rollover from which a very large (D3) hard slab avalanche was triggered by a small explosive on an ESE near treeline. Crown depth 2-6 ft. 
Very large (D3) hard slab avalanche triggered by a small explosive on an ESE near treeline. Crown depth 2-6 ft.  Ski Patroller for scale.
Very large (D3) hard slab avalanche triggered by a small explosive on an ESE near treeline. Crown depth 2-6 ft. 
Report
Heather Canyon

Snowpack Observations

Today I went out to check out the explosive triggered D3 in Clark Canyon and to to gather info on snowpack structure before heading into a warmer regime.

Completed a crown profile at the sight of the Accordian Bowl avalanche @ 6000 ft, ESE aspect. This avalanche is characterized as a HS-AE-R4-D3-I. This hard slab occurred on a heavily loaded slope and failed on a softer layer (4F-) of decomposing particles just above ( 6 inches) the 3/31 MF crust. Max crown depths measured 5 ft and tapered to 2 ft in its shallower spots. This avalanche was approximately 400 ft wide and ran 600 ft. Check out photos for more details.

Skiing around I observed smaller explosive triggered soft slabs in wind drifted snow. These smaller avalanches were generally 4-8 in deep on leeward aspects above 6500 ft.

Digging around on Pea Gravel Ridge, I observed a fairly strong upper snowpack above the 3/21 crust. Snowpack test yielded unremarkable results. Most aspects I traveled on (minus northerlies) have a thin surface sun crust. Northerly aspects are still holding preserved, cold snow. In isolated, sheltered area BTL I observed a fresh batch of SH.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wind Slab
Isolated
Specific
Widespread
Unreactive
Stubborn
Reactive
Touchy
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Comments: We have 2 flavors of wind slabs out there. The softer, shallower ones that formed in the last 24 hrs. And the bigger, hard slabs that formed in more exposed areas in the last 24-48 hrs. These larger hard slabs are gaining strength and stubborn to trigger.
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