Northern Lights Possible Saturday Night Over Washington

WASHINGTON — Washingtonians could catch a sight of the Northern Lights Saturday night as the National Oceanic and Atmospheric Administration has issued a geomagnetic storm watch for Saturday, noting that the aurora could be visible as low as Pennsylvania to Iowa to Oregon.

The storm is classified as a "G3" or "strong" on the Space Weather Prediction Center's five-point scale, and previously the aurora has been seen as low as Illinois and Oregon with a storm of that strength.

That's a good sign for the PNW: a weaker "G2" storm earlier this month produced a dazzling show above Western Washington, and this storm has an even greater chance of lighting up skies over the Sound.

NOAA explains the storm watch was issued as a response to a coronal mass ejection on Thursday, which the agency says "are large expulsions of plasma and magnetic field from the Sun's corona."

Fortunately, skies should clear up just in time for the big event. After a week of heavy rains and wind, the forecast for the Seattle/Tacoma area is calling for clear skies starting Friday night and running through the weekend.

Light pollution can make the aurora difficult to spot, and the best bet for viewing is to get away from the city to somewhere with a clear view of the northern horizon — though the storm earlier this month was strong enough that sightings were reported even in Tacoma and Seattle.

A NOAA spokesman told Patch the storm is expected to start during daylight hours and if it persists, it will be visible at night. The best chance to view the aurora will be overnight Saturday into Sunday over the northern tier states, the spokesman said.

The Space Weather Prediction Center has a handy explainer for the conditions needed in a particular location to actually be able to see the aurora. Depending on a viewer's magnetic latitude, the geomagnetic activity over a three hour period — measured on a scale from 0-9 — needs to reach a certain threshold for it to be visible.

The prediction center says to pick a city closest to the viewer and note its magnetic latitude. Based on the latitude, the center says to check this map to see how high the geomagnetic activity (Kp) needs to be.

For example, the magnetic latitude of Seattle is 52.7. The Kp needs to be at least 7 for the aurora to be visible that low. At present, NOAA expects a Kp of between 6-7 Saturday night, which should be enough for visibility. Space officials say viewers should check the Kp activity before heading out.

However, the Space Weather Prediction Center cautions that skies also need to be favorable with no interference from the moon or city lights.

Lucas Combos contributed reporting and writing for this report.