The so-called Supermoon tends to be over-exaggerated, so to be fair we’d like to call your attention to its exact opposite.
On the morning of November 28, 2012 the full moon (6:46am PST) will occur within four hours of its apogee, the most distant point in its orbit of 252,503 miles (which occurs at 11:35am PST). Last spring, on May 5, the full moon occurred within a minute of reaching actual perigee position of 221,705 miles away making it the Moon's closest approach to Earth in 2012. The close approach of the Moon and its full phase coincide every 412 days. In other words, despite the hype by some sources, the phenomenon of a large Moon isn't that unusual. Many have dubbed tomorrow's event as the "Super Tiny Moon" and I encourage everyone to go outside at moonrise to see just how small the Moon can be - or if you tell the difference at all!
The size of the Moon seen near a horizon is a trick your eyes play on you called "the moon illusion." The illusion is a matter of perception, a trick of the brain, which perceives the Moon as closer when seen overhead when seen on the horizon. When an object is perceived to be nearer, the brain may compensate by making it look smaller to us. Likewise, an object thought to be farther away will be seen as larger.
Interestingly enough, a penumbral lunar eclipse will also occur on the morning of November 28. Unfortunately for Portland, the lunar eclipse will have ended by the time the moon sets in west. The Earth’s shadow has two parts: a dark inner umbra and a lighter surrounding penumbra. It’s this lighter penumbral shadow of Earth that the moon will enter on November 28, 2012. Some viewers cannot detect a difference on the moon’s face during a penumbral eclipse, even while the eclipse is in progress. Others will walk outside, unaware that an eclipse is happening, and say, “Hey, what’s going on with the Moon?!”
For Portland viewers, first contact with the penumbra occurs at 4:14am PST with the moon 30 degrees above the western horizon and will not be visible to the naked eye. The greatest eclipse will be at 6:33am PST as the moon is just 7 degrees above the horizon. For about 30 minutes before and after the eclipse’s maximum, a light grey shading will be seen along the moon’s northern limb. The moon will set at 7:29am PST with the eclipse in progress. The last contact with the moon leaving the earth's shadow will be at 8:51am PST at 12 degrees below the horizon.
The next total lunar eclipse will occur near midnight of April 14, 2014. It will be easily visible for all of the Pacific Northwest!