Observation: NWAC Forecaster

All Observations

Basic Information

Observation Details

Observation Date:
February 5, 2023
Submitted:
February 5, 2023
Observer:
NWAC Forecaster - Katie Warren
Zone or Region:
East Central
Location:
Mission Ridge (4500-6700ft; Primarily N & E aspects)

Signs of Unstable Snow

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

Media/Attachments

In steep terrain, small dry lose avalanches ran quickly and easily.
Snow profile from a sheltered area below Mission Peak at 6500ft.
Shovel Tilt Test produced Q1 sheers with easy force on a layer of buried surface hoar 15cm deep.
A more recently buried (1/18) layer of surface hoar is down about 15cm. Small column tests produced sudden collapse results on this layer. (CTM 11 SC)
Although I went beyound the standard loading steps for this ECT, it propagated and failed failed at 31 on the 1/4 layer of buried surface hoar.
This is an older layer of surface hoar (1/4) buried about 60cm deep below the MLK crust. Although beyond the standardized loading steps in an ECT it produced a sudden collapse, propagating test result. (ECTP31)

Advanced Information

Weather Summary

Cloud Cover:
Overcast
Temperature:
30°F
Wind:
Light
New/Recent Snowfall:
Overnight storm totals were just around 10cm

Light precipitation in the morning shortly gave way to a brief period of broken skies and good visibility. After midday, low clouds drifted in, obscuring the surrounding peaks once again. Winds were light during the morning hours and no blowing snow was observed.

Snowpack Observations

It was a nice day to get up into the upper elevations to look at the recent storm snow and any wind transport or wind-affected surfaces. The new snow was light and just deep enough to cover scratchy, icy old surfaces. Most notably, there was little wind affect. Although on steep terrain, it was easy to get small dry loose avalanches running respectable distances. These dry loose avalanches were the only signs of instability we observed during the day.

A pit dug at 6500ft on a E aspect showed a robust snowpack for the Wenatchee Mountains. HS was 230cm. Most of the upper snowpack consists of 1F to P hard, rounded grains with two notable layers of buried surface hoar, one below the MLK crust (Jan 4th Surface Hoar) and one above (Jan 18th Surface Hoar).

The Jan 18th surface hoar layer is buried 15cm deep and showed sudden failures in a compression test (CTM 11 SC), but did not propagate in an extended column test (ECTN 9). The Jan 4th surface hoar layer is buried below the MLK crust and produced a sudden collapse on a compression test (CTH23 SC). In an extended column test, this layer did not propagate in the standardized 30 loading steps of the test. However, upon an additional extra loading step, it failed suddenly and propagated (ECTP 31 SC). While outside of the bounds of this test, it is still a notable result.

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