Nice pics there Roger.. The interesting thing about these is that the evaporation of the moisture in the descending air causes cooling and this sometimes results in microbursts on the ground.
Any WA people (or anyone else for that matter) interested in the weather and related subjects is welcome to join us on our little 'waweathergroup' forum.. we are a friendly bunch..
http://waweathergroup.com/forum/index.php
A recent post on there showed an example of this Virga cloud formation as well..