Pro Field Report

Basic Information

Observation Details

Observation Date:
April 9, 2023
Submitted:
April 9, 2023
Observer:
SAC - Scott Savage
Zone or Region:
Banner Summit
Location:
Hailey to Swamp Ck near Banner Summit (many aspects and elevations)

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
Isolated
Mostly glassing observations, except for near road obs and some skiing around the flats near Marsh Ck/Swamp Ck. Extensive previous cracking and collapsing (continuous for several km) just below the upper 1cm crust in Marsh Ck. All recent avalanches we saw were D1 (small) wet loose.

Bottom Line

From 8 AM - 4 PM: The natural wet loose activity was more widespread today than yesterday, but the slides were almost entirely D1-D1.5 (small to medium, not big enough to bury someone unless they were in an ugly terrain trap). Since I returned home around 4 PM, I did not get to see the effects of the late afternoon-evening heat and sun; wet snow stability changes rapidly, so take any observations (including this one) with a grain of salt this week.

Advanced Information

Weather Summary

Cloud Cover:
Partly Cloudy
Temperature:
20s F around 9AM, 50s F around 4PM
Wind:
Light
New/Recent Snowfall:
No new snow in past 24 hrs. Several inches of dry snow from Sat night underneath surface crust around Marsh Ck.

CLR to PC with increasing clouds this afternoon. Mostly mid and high level clouds, so no greenhousing. No snow available for transport where we were.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Photos Details
1 Apr 9, 2023
(+/- 1 day) 		Pole Ck: peak opposite Grand Prize Gulch
SE 9400ft 		D2.5 WS-Wet Slab O-Old Snow 3ft N-Natural
This thick, wide avalanche released naturally in the Pole Ck drainage, likely on Sunday April 9th. The hot, sunny weather likely played a role in this slide.
Report
1 Apr 9, 2023 8:20 pm
(Exact) 		Warm Springs Ck - near Board Ranch
SE 6200ft 		D1.5 WL-Wet Loose N-Natural
This small wet loose avalanche blocked Warm Springs Ck near Board Ranch on Sunday afternoon, April 9th. E/SE aspect near 6200'.
Report
1 Apr 2, 2023
(+/- 3 days) 		Northern Sawtooths: McGown-Mystery cirque
NE 9400ft 		D2.5 HS-Hard Slab O-Old Snow 5ft N-Natural
This very large avalanche released naturally in the northern Sawtooth Mtns near Mystery and McGown peaks, likely around April 1-4. NE aspect near 9400'.
Report
1 Apr 2, 2023
(+/- 3 days) 		Salmon River Headwaters - SW of Camas County High Point
NW 10100ft 		D3 HS-Hard Slab O-Old Snow 4ft N-Natural
This very large avalanche likely released around April 1-4 in the Salmon River Headwaters on a NW aspect near 10,100'.
Report
Pole Ck: peak opposite Grand Prize Gulch
Warm Springs Ck - near Board Ranch
Northern Sawtooths: McGown-Mystery cirque
Salmon River Headwaters - SW of Camas County High Point

I did not list the many (20-50?) D1-1.5 wet loose slides we observed today. Several were triggered by small cornice chunks. There were a few small wet loose that gouged down to near the ground where the snowpack was thin (Carbonate E aspect, other rocky areas).

Snowpack Observations

No snowpack tests performed.

Surfaces: Near Banner Summit flats = 1cm P hard crust above 15-20cm of dry DF. In areas where there was less snowfall in the past 48 hrs, the surface became mushy and unsupportable by early afternoon. I did not fall in above my knees (boot and ski penetration) anywhere.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Wet Loose
Isolated
Specific
Widespread
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: surficial (5-25cm?)
Comments: Shaded area indicates where we observed the most natural activity by 4 PM. At upper elevations, E-SE-S-SW were most active. At middle and lower elevations, the pattern was less clear today. Direct solar input was driving the problem this morning, but afternoon activity seemed less dependent on direct sunshine.

Terrain Use

We did not plan to be in avalanche terrain today, including run out zones.