Winter Again

Went to Noisy Basin to watch the cold front come in.

• Before the storm:
  • Despite temperatures not dipping below freezing last night, and the surface being wet at mid elevations this morning, the most recent melt-freeze crust was stout and supportable. Boot penetration was only 3 cm. The crust covered all aspects and elevations.
  • Snow line was between 4,500 and 5,400 feet, depending on aspect.
  • Sheltered, shady slopes at mid elevations had about 2 inches of dry snow from the last Canadian cold front on the 18th-19th atop the crust.
  • The snowpack under the crust consisted of moist to wet melt forms on south aspects and settled dry snow with a few graupel and facet layers on north aspects. See photo and snowpack tab.
  • I found a few rocky areas in alpine terrain where the snowpack is thin, around a meter deep, and consists entirely of weak facets below the recent crust.
• The front crossed the Swan Divide around 9:30 am when winds and snowfall started.
  • Temperatures quickly dropped below freezing. Snowfall increased quickly with periods of about an inch per hour.
  • Winds became moderate to strong from the northeast and moderate to intense blowing snow was a constant on ridgelines above 6,000 feet.
  • New wind slabs developed quickly on south-facing slopes. These were thin, but regularly cracked around me on test slopes.
  • On sheltered windward slopes I easily triggered loose dry sluffs. These were small, running about 100 feet, because there wasn't much snow to entrain.
  • It snowed 2 inches by the time I left in the early afternoon.