Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
January 30, 2022
Submitted:
January 30, 2022
Observer:
NWAC Forecaster - Matt Primomo
Zone or Region:
Stevens Pass
Location:
Skyline to Smithbrook (all aspects 3200ft to 5,600ft)

Signs of Unstable Snow

Recent Avalanches? 
None Observed
Cracking? 
None Experienced
Collapsing? 
None Experienced

Media/Attachments

Typical profile within the upper 6" of snow on W-N-E aspects above 4,700ft. This was at 1:45pm.
Crust facet sandwich: Thin sun crust over dry, faceted snow over a thicker rain crust on a SE aspect at 4,400ft in open treed terrain.
View across the SE slopes of Tye Peak towards the highway 2 corridor and inversion layer below.
Cold air was pooled below around 4,700ft all day. This preserved dry, faceted snow at and below this elevation.
Gloppy, moist snow with light rain and wet snow mix at around 1pm at 5,400ft.
Slopes below the north side of Lichtenberg. Less snow from the 1/20 storm and perhaps some wind exposed some of the older rain crust directly in some areas.
Very large, feathery surface hoar was found in open, flat terrain at the bottoms of valleys. Freezing rain encased them in ice.
Very large feathery surface hoar found in flat terrain at 4,700ft.

Advanced Information

Weather Summary

Cloud Cover:
Overcast

We had a little bit of everything, besides strong winds. In the morning the sun poked through at times. Skies became fully overcast and a few snow/rain showers passed through. No significant snow accumulations during the day. The most notable thing was that below around 4,700ft the cold air pool stayed in place while we were out. Mixed rain and snow occurred with passing showers, but below the inversion we encountered freezing rain and sleet.

Snowpack Observations

A trace of new snow had fallen at some point before we arrived in the morning. Snow surfaces warmed during the day at upper elevatons, and by the time we skiied off the north side of Tye Peak we were managing potential for small wet loose avalanches and rollerballs in 10 day old snow. Above 4,700ft the weakest snow observed was on direct north aspects. Small near surface facets appeared to be rounding during the day and were about 0.5mm on average, but larger in some starting zones. Although snow surfaces became moist or wet from light rain, dry facets were preserved just below on most slopes and rested above the stout rain crust from 1/20. In most open areas the rain crust was quite smooth, and will make a good bedsurface for avalanches to run on. The overlying faceted grains appeared moderately well bonded to the rain crust. On a NE aspect at 5,400ft a tilt test popped the moist snow off the dry faceted grains in a planar failure with moderate force (5cm down from the surface, and 10cm above the 1/20 rain crust).

Below 4,700ft in elevation snow surfaces largely remained dry on all aspects, and became capped with a thin, breakable freezing rain crust later in the day. On flatter, open areas below the inversion there were crops of very large (3cm) feathery surface hoar. These became encased in ice from a layer of freezing rain and were quite strong.

The skiing became gloppy and sticky above the inversion on W-N-E aspects, but was quite good and fast below the inversion layer. Open slopes with SE-SW aspects above the inversion were softening up and would've still skiied like corn today.

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