The supermoon will rise Sunday, but will we see it?

A supermoon rises behind Mount Baker in October, 2014.
A supermoon rises behind Mount Baker in October, 2014. The Bellingham Herald file

The only supermoon of 2017 rises Sunday, but you may need help to see it: Western Washington’s forecast is for rain and partly cloudy skies this weekend.

Known as the “full cold moon” – the Haida of the Pacific Northwest called it the “Snow Moon,” or “Ta’aaw Kungaay,” a nod to December weather – it’s what astronomers call a perigean full moon. The full lunar face is illuminated when the moon is at perigee, or when it’s closest to the Earth in its elliptical orbit. Due to an optical effect known as the moon illusion, this makes Earth’s moon appear up to 14 percent bigger and 30 percent brighter than normal, according to Space.com.

The best time to see a supermoon is after moonrise when the moon is just above the horizon – about 4:56 p.m. Sunday in Whatcom County – because it’s size contrasts well to much of the region’s landscape . The sun sets at 4:15 p.m. that same day, so the moon will rise in twilight.

The moon’s gravitational pull also affects tides, and on Sunday the difference between low and high tide will be dramatic.

The high tide at 3:21 p.m. will be 9.07 feet, while the low tide at 10:44 p.m. will be minus 2.36 feet.