The Full Moon happens tomorrow morning at 4:28 a.m. EDT. However, we won't be able to see the completely Full Moon due to an approaching Alberta Clipper, which will bring the potential of two-to-four inches of snow to the region. Skies will be mostly cloudy late tonight with light snow expected during the morning commute. The December Full Moon is known by a variety of names, including the Full Cold Moon and the Full Long Night Moon.
Why is it called the Full Long Night Moon? During December, the Winter cold fastens its grip in the Northern Hemisphere, and nights are at their longest and darkest. The term Long Night Moon is also an appropriate name because the early Winter night is long, and because the Moon is above the horizon for a long time. The midwinter full Moon has a high trajectory across the sky because it is opposite a low Sun.
In fact, the December Full Moon has been referred to as the Oak Moon, the Frost Moon, the Cold Moon, and the Moon Before Yule. No matter what the name, the Full Moon in December is directly opposite the Sun; therefore it is out for a long time. Since the Moon appears to follow nearly the same path as the Sun in the sky, the amount of time the Moon spends above the horizon varies as it orbits the Earth. The Moon is Full when it is opposite the Sun in the sky, so a Full Moon rises roughly at sunset and sets at sunrise. Therefore, we only see Full Moons at night.
Six months from now, on the Summer Solstice, the longest day of the year when the Sun spends the most time above the horizon, the Full Moon spends the least amount of time above the horizon. On the other hand, on the Winter Solstice, the shortest day of the year when the Sun spends the least time above the horizon, the Full Moon spends the most amount of time above the horizon. The time spent above the horizon each night for the Full Moon varies throughout the year about as much as the length of the day.