11th Annual Utah Snow & Avalanche Workshop Open and Motorized Sessions Oct. 27th.
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Observation Date: 
4/4/2017
Observer Name: 
Joey Dempster
Location Name or Route: 
Big Springs, South Fork of Provo Canyon
Weather
Sky: 
Scattered
Wind Direction: 
North
Wind Speed: 
Moderate
Weather Comments: 
Cool despite strong sun in the morning. Moderate ridge top winds out of the north kept a lid on heating. Clouds moved in around 3pm and really shut down the warming, refreezing the south facing corn that had developed through the day.
Snow Characteristics
Snow Surface Conditions: 
Dense Loose
Wind Crust
Melt-Freeze Crust
Damp
Snow Characteristics Comments: 

Typical spring mixed bag today.  Supportable crusts on sun exposed slopes, dense powder remaining on sheltered north facing slopes above 8000 feet, and breakable crust (both sun and wind related) on exposed mid and high elevation slopes.

Corn developed nicely on due south facing slopes around noon, but quickly refroze a few hours later when clouds moved in.  So it was barely warm enough today to melt the surface snow.  I would expect that at the highest elevations, not even south facing slopes experienced surface melting.  

Powder could be found in patches and it was stable, but it was the exception, as most north facing snow had a breakable wind crust that made skiing challenging.  However, your favorite high sheltered spots could easily still have good powder tomorrow if they stayed out of the wind.  It was sufficiently cold again today to preserve it. 

Comments: 

Overall stability is good, and I found that the low hazard forecasted for the day was accurate. South facing slopes up to 9500 feet received enough heating yesterday to consolidate and refreeze into a supportable surface.  On the north facing slopes that held powder, there was no evidence of instability from isolated columns, ski cuts, and skiing in 35 degree terrain. There were widespread wind crusts, but they were shallow and breakable, 1-2 inches in depth and not an avalanche hazard, just poor skiing!

On north facing slopes there is ~16 inches of new snow on top of the mid-March consolidated surface (which is effectively the ground).  Within that 16 inches, there is a shear plane that is visibile, but does not produce clean shears in tests.  Small facets are visible in this layer, but it isn't overburdened at the moment, and I think it will heal before it gets another load on it this weekend.  But I would be looking for it once it snows again.

Wind was out of the north today, but I observed no snow transport.  

Also of interest (although probably primarily academic), is the widespread shallow slab avalanches that I observed around 8500-9000 feet.  There were probably a dozen, all on the same aspect and elevation band, that probably ran yesterday.  I have attached a picture of one of them.  They appear to be only 3-4 inches in depth, but they were wide enough that they could have potentially buried a person, even if not deeply.  I suspect they ran yesterday when the sun came out, and it appeared that the hazard was diminished by heating and refreezing overnight, because skiing similar slopes did not produce an signs of instability.  Still, it was interesting and a reminder that "low doesn't mean no", and shallow slabs can still pack a punch if they propagate wide enough.  

Bottom line: low hazard on all aspects up to the observed elevation of 9500 feet.  Hazard will be low again tomorrow, with a rising danger of wet avalanches as it finally warms up (this will be the first warm day since the last snow event, so there will be new snow that could be shed as it warms up).  North facing slopes should provide decent powder skiing with low slab avalanche hazard.

Today's Observed Danger Rating: 
Low
Tomorrows Estimated Danger Rating: 
Low
Snow Profile Coordinates: 

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