UFO's land and at flight during a overcast morning...

I was twelve years old at the time; wrangling with my father at Lake Amanor. When these diamond shaped UFO's. The UFO's had unusual dark colors. they where on the opposite side of the lake hovering then appeared to land inside a gully. At some point I recall they decended and acended very quickly. The morning was overcast, so when the blue sky appeared the UFO's moved quickly.  A sheriff arrived telling us we had to leave the area. My father described at night while driving in the area he was or almost abducted at night the UFO chased his international travelall.