Sitting outside. Overcast. Noticed a long oval shaped black spot in the clouds. Wathched for approx 30 seconds and called girlfriend out to see. As soon as I told her, it began to appear to ascend through the clouds. She only saw it for about 10 seconds as it disappeared. Freaked her out, though. I look at the sky every night and this was definitely strange. Most of the sky was a solid patch of clouds with no breaks and this spot (darker than the night sky) was very visible until I told someone to check it out.