Pro Field Report

Basic Information

Observation Details

Observation Date:
December 28, 2022
Submitted:
December 29, 2022
Observer:
SAC - Davis
Zone or Region:
Galena Summit and Eastern Mtns
Location:
Prairie Peak (Primarily S-SE-E-NE, 7,000-9,400')

Signs of Unstable Snow

Recent Avalanches? 
Yes
Cracking? 
Isolated
Collapsing? 
None Experienced
Avalanches refer to a small storm or wind slab on the N side of Griffin Butte (see below). Cracking in isolated wind-drifts near the summit. I didn't travel through a lot of wind-drifted terrain. Stability between Fair and Good.

Snow Stability

Stability Rating: 
Good
Confidence in Rating: 
Moderate
Stability Trend: 
Steady

Bottom Line

With somewhat limited visibility, I did not observe natural avalanches in the southern Boulders or Smokys near Prairie Ck. A weak layer of snow buried 1.5 to 2' deep was concerning particularly on wind-loaded slopes.

Media/Attachments

Prairie Peak, ESE at 8,600': This faceted rain crust was buried on December 19th. It produced ECTP 7 and 11.
Prairie Peak, ESE at 8,600'.
Prairie Peak, ESE at 8,600'.
There are numerous weak layers under the recent storm snow. In this pit the rain crust that was buried on (12/19) was the most worrisome.
Small avalanche on NE facing slope of Griffin Butte @ 7,400'.

Advanced Information

Weather Summary

Cloud Cover:
Mostly Cloudy
Temperature:
20s F
Wind:
Light , NW
New/Recent Snowfall:
HST = 35-50 cm, HN = 15 cm

Light wind from the W and NW. 15 cm of low-density snow available for transport, more than that with strong wind. Very light snowfall during daylight hours with no real accumulation.

Avalanche Observations

 #  Date Location Size Type Bed Sfc Depth Trigger Comments Photo
1 Griffin Butte
NE 7,400 		D1.5 SS N-Natural
Small avalanche on NE facing slope of Griffin Butte @ 7,400'.

Snowpack Observations

Rain line, New/Old, Surface Obs: There was ~15 cm of low density (F-) snow over 20-30 cm of heavier (4F) snow. The new/old interface was a rain crust below about 7,300' that disappeared by 7,500'. Above that it was a stout 3 cm melt-freeze crust (sunnier slopes) or rounded grains (shaded slopes), or something on a continuum between the two. It did not produce any concerning results and was well-bonded where I dug.

ESE @ 8,700', HS = 135 cm, HST = 53 cm: This pit was in a mostly sheltered small clearing."12/19" dn 53 cm produced ECTP 7, 11 under a faceting, brittle rain crust. (See photos). "12/8" was detectable as a half-step hardness change and subtly more faceted but produced ECTX. "11/27" was rough, moist and 4F+. It produced ECTX and CPST28/100 end.

There are numerous weak layers under the recent storm snow. In this pit the rain crust that was buried on (12/19) was the most worrisome.

Avalanche Problems

Problem Location Distribution Sensitivity Size Comments
Persistent Slab
Isolated
Specific
Widespread
D1
D1.5
D2
D2.5
D3
D3.5
D4
D4.5
D5
 Layer Depth/Date: 35-50 cm, 12/19
Weak Layer(s): Dec 19, 2022 (FC)
Comments: I suspect 12/8 would also be on my radar had I traveled on more shaded aspects. Seems most likely to be triggered where a fresh wind slab rests near the surface. That said, Scott was getting ECTPs on this layer prior to the storm.

"11/27" is buried more than a meter in this region beneath a 1F+ slab and is somewhere between stubborn and unlikely to trigger.

Terrain Use

I felt comfortable on short, supported, steeper slopes without an obvious recent wind-load. I avoided wind-loaded terrain. Steep W-N-E still give me the most hesitation due to a higher number of better developed weak layers.