What is the moon phase tonight?

A waning (shrinking) gibbous moon rises between the sunset and the midnight, and sets after sunrise.

The waning gibbous is the moon phase after the Full Moon. It lasts until half of the Moon's surface is illuminated at the phase called Third Quarter or Last Quarter.

In other words, the waning gibbous starts with a moon illumination of 99.9% and reduces down to 50.1%.

This phase took the name "gibbous" because of the shape of the illuminated (visible) part of the moon which is greater than a semicircle and less than a circle.

This transition lasts about a week, which is approximately the 1/4 of the moon period.