Winds out of the Southwest seem to have kept much from happening last night. Some small signature is seen after sunset but dissipates by midnight, possible due more to atmospheric causes. Below is some information provided by Greg Thompson (the Guru behind the ncar website).

Greg wrote:
” Don’t forget that some echo comes from insects not always birds (though the two often go
hand-in-hand – food chain thing) AND, MORE IMPORTANTLY, that
some echo comes from A.P. (anomalous propagation) whereby the
radar energy is scattered by a large difference in air density
then off the actual terrain surface before being measured at
the radar site. This type of echo is probably hard to tell from
birds/insects under the right circumstances. That air density
difference can arise when the nighttime inversion starts to
occur which is why the radars all light up at sunset from
east to west and vice-versa at sunrise. “