The supermoon shines brightly through the clouds in June 2013. (Kevin Ambrose)

The last full moon of 2017 will appear especially plump and vibrant in the night sky this weekend.

As it reaches fullness, the moon will also be making its closest approach to Earth around the same time, designating it a “supermoon.”

Because of the moon’s extra-close approach to Earth, it will appear about 14 percent bigger than if it were at its farthest away point in its orbit. It will shine up to 30 percent brighter, not only because it’s close to Earth, but also because Earth will be nearing its closest to the sun in early January.

“The sunlight reaching and reflecting off the Moon this time of year is about 7 percent more intense” than in the summer, explains NASA.

The moon officially turns full at 10:47 a.m. Sunday, but it will look full or very close to full to the naked eye Friday, Saturday and Sunday nights.

December’s full moon is known as the Cold Moon or Frost Moon because of the cold weather at this time of year. It is also sometimes referred to as the Moon Before Yule (Yule is an old northern European winter festival, associated with Christmas).

 

While this supermoon is 2017’s one and only, 2018 will start with two in succession. Supermoons are set to occur twice in January, on the 2nd and 31st. When two full moons occur in the same month, the second is sometimes called a blue moon or, in this case, a super blue moon.

EarthSky notes this January super blue moon “will pass right through the Earth’s shadow,” making for a super blue moon eclipse!

Astrologer Richard Nolle defined a supermoon in 1979, but the term has really taken off in the past few years. Nolle said that a supermoon is a new or full moon that occurs when the moon is within 90 percent of its closest approach to Earth, known as perigee, in a given orbit.

In Washington, D.C., moon rise in the eastern sky will occur at 3:42 p.m., 4:26 p.m., and 5:15 p.m. Friday, Saturday and Sunday nights, while  moon set occurs at 5:35 a.m., 6:47 a.m., and 7:58 a.m. Saturday, Sunday and Monday mornings.

The cloud cover forecast Friday, Saturday and Sunday nights, shown below, offers a good general sense for the areas that can expect clear skies. The good news for much of the Eastern Seaboard is that clear to partly cloudy skies should prevail during this period, except for Saturday night in the Northeast. More extensive cloud cover is forecast in the Pacific Northwest and Great Lakes regions throughout the period.


Cloud cover forecast from GFS model Friday, Saturday and Sunday nights.