We had an accident today at the Y.  No reports have been filed and we don't know much.  What we do know is that the winds aloft forecast for the area was 21mph at 12k ft.  Measured winds at Baldy (11k ft) between 7AM and 5PM were consistently between 22mph and 29mph with gusts in the low to mid 30s.  By 6PM winds were 38mph gusting 54mph.

From the Book of Risk:

Mechanical turbulence and rotor downwind of obstacles start with winds at about 9 miles per hour.  At 12 miles per hour that turbulence has the strength to collapse a paraglider.  At 15 miles per hour the collapses become difficult to block.  At 18 miles per hour even the very best among us will begin to lose their wing. 

Conservative winds aloft numbers for intermediate pilots for the the Wasatch are 

12 mph at 12K ft.
  9 mph at 9K ft
  6 mph at 6k ft

Flight in known/knowable turbulence

On February 5, 2020 an intermediate pilot landed downwind through a switching wind directions and hit the ground hard enough to cause serious bruising.

The pilot hiked to the top of the North Side and noticed the wind at the top had switched from 4mph out of the northwest to 3mph out of the Southwest.  After kiting along the road at the top the pilot launched downwind.  Soon after launching the pilot encountered leeside thermic lift.  Not expecting lift the pilot turned west.  The lower wind sock was showing light northeast wind.  Despite the lower wind sock direction the pilot noticed his approach landing speed was above 30mph.  Suddenly the pilot's glide angle dropped more quickly the last 20 feet and unable to complete a flare he hit the ground hard.

Switching base wind with leeside thermals pulling localized wind toward the thermal core made a complex mix of convoluted air for the pilot to fly through.  From his description it is likely that he was flying in zero to light downwind air into stronger down wind air with the transition causing the sudden drop similar to flying through a wind gradient.

Strong thermals will always mess up what we believe the local wind direction to be.  Nonetheless, the safest conditions are with base winds consistent in both strength and direction or no wind at all.  The highest risks come with high winds followed closely by switching winds.

From the book of risk:

Turbulence can be knowable with some education in weather and wind effects.  Study the weather a lot, read a lot of books about weather especially that related to paragliding and hang gliding:

Understanding the Sky by Dennis Pagen

Thermal Flying by Burkhard Martens

Mastering Thermaling by Kelly Farina

Weather for Dummies

Flight Outside of Conservative Equipment Choice Parameters

This Spring between 5PM and sunset in mild conditions:

A P2 Novice pilot flying an EN C glider crash landed on the face of the lower ridge of the North Side.  Although the impact split the pilot's helmet, no immediate medical attention was required.

The apparent factor involved in this accident is equipment choice.  Higher classes of gliders spin and stall more easily than lower classes of gliders.  Many hours of flying are required to develop the muscle memory required to keep higher-aspect gliders open under duress.  

From the Book of Risk:  (Flight outside of Conservative Equipment Choice Parameters). 

Problematic equipment choice involves flying an EN class paraglider without adequate education, experience or annual flight hours to prepare for the challenges of flying that class.

Experience recommendation for the EN C class:

500-1000 hours EN C 

Annual flying hours recommended for the EN C Class:

150 hours EN C (wear this glider out)