Strong geomagnetic storm could bring northern lights to Pennsylvania: forecast

(NEXSTAR) — Skywatchers across at least 18 states may have the chance to see the northern lights on Tuesday as a coronal mass ejection impacts Earth.

NOAA’s Space Weather Prediction Center has been tracking the coronal mass ejection, or CME, since Sunday. Tuesday morning, the SWPC said early signs pointed to the CME barreling through space “in the general direction of Earth.”

“This raises our measure of confidence in a geomagnetic storm,” the SWPC wrote on X. Ahead of the CME’s expected arrival, the SWPC has issued a G3 geomagnetic storm watch through Wednesday, citing “the arrival of multiple coronal mass ejections.”

Weaker conditions are expected to last into Thursday.

Tuesday night, however, you may have a chance to see the northern lights — if you live far enough north.

The latest aurora viewing forecast from the SWPC, seen below, shows the likelihood of seeing the northern lights in North America. Canada and Alaska have the greatest chance at catching the dancing lights in the sky, as usual. Still many across the Lower 48 have at least a slim chance at seeing the aurora.

Forecasting suggests you may be able to see the aurora, especially along the northern horizon, if you’re in Washington, Oregon, Idaho, Montana, Wyoming, North Dakota, South Dakota, Nebraska, Minnesota, Iowa, Wisconsin, Illinois, Michigan, New York, Vermont, New Hampshire, and Maine. Even those in the northern portions of Indiana, Ohio, Pennsylvania, and Massachusetts could catch a glimpse of the northern lights.

Geomagnetic storm conditions are expected to increase between 6 a.m. and 9 a.m. UTC (or 2 a.m. to 5 a.m. EDT), Wednesday morning, per the SWPC’s forecasting. The forecast shows a peak Kp index — used to measure the strength of the geomagnetic storming — of 6 between 12 p.m. and 3 p.m. UTC (8 a.m. and 11 a.m. EDT), a less-than-ideal time for us, since the aurora are largely invisible to us during daylight hours.

However, conditions could remain strong enough for some to see the northern lights Wednesday night.

As of Tuesday afternoon, the SWPC aurora forecast shows many of the same states could get a second light show Wednesday:

Because forecasting space weather is difficult until CMEs are closer to Earth, it’s possible the forecasting will change. You can follow the SWPC’s forecasting online.

When the geomagnetic storm conditions are weaker, and the aurora-spotting likelihood lower, experts recommend looking at the northern horizon to get a glimpse of the celestial show. You may have to use your smartphone to see it, since those devices are more sensitive than our eyes.

What is a CME?

The northern lights appear when coronal mass ejections are hurled out by the sun, sending plasma and magnetic material to collide with Earth’s magnetic field. Particles flow along the currents to the poles, interacting with oxygen and nitrogen in the atmosphere.

Those interactions form excess energy, which appear as bursts of light we know as the aurora. The gases involved and where the action is happening determine the colors that we see.

That activity in our atmosphere is known as geomagnetic storming. The stronger the storm, the further south the northern lights can be seen. Geomagnetic storms are measured on a five-point scale, ranging from G1 to G5.

Minor-level storms, even up to G3, are not uncommon. Some of the strongest storms in recent years happened last May, bringing the northern lights as far south as Florida.

Later this month, another celestial event will arrive in the sky: a rare “smiley face,” if you will. You’ll have only a narrow window of time to see it, however.