as if some of the clouds had been wiped away along a straight edge.
It was probably just crepuscular rays* that happened to have very wide bands of light and shadow.
In my sky folder, and I found these images of more typical looking rays:
On Monday evening, I followed a ray of light from the sunset in the west...
all the way across the sky...
to the east where subtle rays appeared to converge opposite the setting sun.
(The white dot is the moon.)
|anti-solar crepuscular rays|
*It is interesting to note that although sun beams seem to radiate outwards, it is an illusion. Rays of sunlight are parallel to each other like rails on a train track that appear to converge at a vanishing point at the horizon.
See more sky images from around the world at Skywatch Friday.