Pro Field Report

Basic Information

Observation Details

Observation Date:
February 20, 2023
Submitted:
February 21, 2023
Observer:
SAC - VandenBos (off duty)
Zone or Region:
Banner Summit
Location:
Copper (6,700-9,000, primarily northern half of compass)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced
No hard signs of instability.

Snow Stability

Stability Rating: 
Very Good
Confidence in Rating: 
Moderate
Stability Trend: 
Worsening

Advanced Information

Weather Summary

Cloud Cover:
Overcast
Wind:
Moderate , W
New/Recent Snowfall:
4-5cm at upper elevations, 1-2cm at highway level.

Afternoon wx obs: today was a bit warmer than forecast. Gusty, moderate winds occasionally digging down to the highway, with more consistent winds blowing in exposed upper elevation terrain. Tough to gauge HST due to amount of wind transport and thin rain crust, estimated around 4-5cm. Above about 8,000' I climbed into a zone of 100% RH where I was actively being rimed on. Very light snow was falling up here, almost more of a semi-frozen mist. New rime feathers up to 15+cm long had been deposited above 8,000', with feathers growing to the west. Today's weather did not significantly affect the avalanche hazard, but it did have a notable effect on the snowpack.

Avalanche Observations

No avalanches observed, though visibility was poor.

Snowpack Observations

This was a quick tour at the end of the day to see what the weather was up to. When I departed the car around 1600 I found moist to wet snow in the upper 5-10cm of the snowpack. It was initially difficult to tell if the snow had become wet from warm ambient temperatures, from ambient solar radiation, or from wet snow/rain. Climbing upwards, a crust appeared on the surface of the snowpack around 6,900'. This was a true rain crust (IFrc), with a thin water-ice lens (1-2mm thick), that extended all of the way to the top of Copper (~9,000'). This crust thinned a bit as I climbed, but was clearly present up into upper elevation terrain. When I descended shortly after sunset I found that the snowpack at highway level had also crystallized into an IFrc. Neat, but kinda gross. There was a trace of snow on top of this crust down low and 2-3cm of dry snow on top of the crust up high. I suspect the rain came with a short duration pulse of very warm, wet air sometime in the afternoon.

In exposed middle and upper elevation terrain, the wind was moving snow around, though there wasn't a lot of snow available for easy transport, thanks to amount of past wind affect and the new crust at the surface. If the wind blows a lot harder it would probably be able to find snow to put into to play.

Avalanche Problems

It was not warm/wet enough to produce wet snow issues here today, but we may not have been that far off.