Observations from Round Top

Location Name: 
Round Top
Region: 
Carson Pass Area
Date and time of observation: 
Fri, 04/20/2012 - 11:00
Location Map: 
United States
38° 39' 58.482" N, 120° 0' 9.0108" W
See map: Google Maps
US


Red Flags: 
Rapid warming
Obvious avalanche path
Observation made by: Professional Observer
Snowpit Observations
More detailed information about the snowpack: 

Evidence of radiational refreeze, with treed slopes in melt phase by 8am, but open slopes exposed to radiational cooling held 10-15cm of very supportable MFcr until mid-morning. This MFcr quickly returned to melt phase due to very warm temps and strong solar input. Previous MFcr beneath last week's storm snow remained frozen and knife hard.

Pic: From provided lat/long. HS 280cm. No free water observed below 30cm from surface at 11am. Supported by informal obs elsewhere in the area. Well defined drainage runnels on all but the steepest N aspects.

Most steep slopes, including N aspects, had evidence of previous roller ball activity and loose wet avalanches. Roller balls initiated today gained significant mass and continued downslope on low slope angles (~20 degrees), but did not entrain additional snow nor reach the previous MFcr.

Steep couloirs on Round Top remained firm into mid-day, with frozen previous tracks creating terrible descending contitions.

Snowpit or crown profile photo or graph: 
Weather Observations
Blowing Snow: 
No
Cloud Cover: 
Clear
Air temperature: 
Above Freezing
Wind Speed: 
Light
Precipitation: 
None
Air temperature trend: 
Warming
Wind Direction: 
Southwest
Accumulation rate: 
None
More detailed information about the weather: 

Minimal afternoon buildup of thunderheads observed, with no precip by our departure at 12:30pm.