How to read a northern lights forecast from Southeast Alaska

Aurora forecasts are full of numbers, and the one most people look at first is the Kp index, a scale from zero to nine that describes how disturbed Earth’s magnetic field is. The higher the number, the farther south the aurora can reach. In Southeast Alaska a moderate number can be enough on a dark, clear night, which is why a forecast that would mean nothing in Seattle can send half of Juneau out to the beach.