Observation: NWAC Forecaster

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Weather Summary

It was a surprisingly mild day compared to the anticipated forecast. Overcast skies and low clouds obscured visibility for most of the morning. As we started the day, precipitation had stopped, with some light snowfall returning as we exited around 12 pm.

There was widespread evidence of previously wind-drifted snow, but we experienced mostly calm winds and did not observe and active wind loading.

Snowpack Observations

There was only around 1" of new snow as we left the car at 4000ft near Blewett Pass. The underlying surface was the thick supportable crust from Christmas.

I used quick hand pits as we traveled to assess the bond with the old snow surface. At lower elevations, the new snow had a favorable bond to the underlying crust and I could not locate any preserved buried surface hoar. At higher elevations, in sheltered northern aspects, the old snow interface was soft with faceting decomposing particles. I could identify surface hoar mixed in with this interface and hand shears, and shovel tilt tests produced moderate resistant planer results.

Wind affected surfaces and stiff, shallow wind slabs were observed even at lower elevations in forested areas. In more exposed locations, windward slopes were scoured down to the Christmas Crust and deeper drifts 30cm thick were found on lee aspects. Kick turns only produced minimal cracking in 4-5" wind slabs, and steep wind-loaded test slopes produced no results.

I dug a quick pit at 5500ft on a north-facing aspect. I found an HS of 90cm, with 5cm of new snow. The Christmas Crust was buried 20cm deep. In this location, the Christmas Crust had formed as two separate crusts with small, 4F, faceted grains in between. No collapsing or signs of instability were observed in this layer. Most of the older facets from November were gaining strength (1F) and rounding, with the exception of void spaces between rocks where pockets of F hard faceted could still be found.