Solar storm watch: Geomagnetic watch issued

An unusually strong solar storm hitting Earth could produce northern lights in the U.S. this weekend and potentially disrupt power and communications. The National Oceanic and Atmospheric Administration issued a rare severe geomagnetic storm warning when a solar outburst reached Earth on Friday afternoon, hours sooner than anticipated. The effects were due to last through the weekend and possibly into next week.

Northern lights were visible in much of the U.S. and across the world Friday.

The National Oceanic and Atmospheric Administration issued a rare watch on Thursday night, warning that the solar flare effects would be worst Friday night but could last all weekend.

"G4 conditions were observed by [Space Weather Prediction Center] around 12:37 p.m. EDT today and significant to severe geomagnetic storming is likely to continue," the agency posted Friday.

The storm could produce northern lights as far south in the U.S. as Alabama and Northern California, according to NOAA. But it was hard to predict and experts stressed it would not be the dramatic curtains of color normally associated with the northern lights, but more like splashes of greenish hues.

Friday night into Saturday, the FOX Weather Forecast Center said skies looked clear for most of the northern U.S. with less than 10% cloud cover expected from the Midwest to the Northwest. However, clouds would be around in the Northeast.

Photos of northern lights across US, world

The aurora borealis, also known as the northern lights, glow on the horizon at Another Place by Anthony Gormley, Crosby Beach, Liverpool , Merseyside. (Credit: Peter Byrne/PA Images via Getty Images)

The aurora borealis, also known as the northern lights, glow on the horizon at St Mary's Lighthouse in Whitley Bay on the North East coast. (Credit: Owen Humphreys/PA Images via Getty Images)

Northern lights can be seen behind a weathercock at Wülfinghausen Monastery near Eldagsen, south of Hanover. (Credit: Bernd von Jutrczenka/picture alliance via Getty Images)

The aurora borealis, also known as the northern lights, glow on the horizon at St Mary's Lighthouse in Whitley Bay on the North East coast. (Credit: Owen Humphreys/PA Images via Getty Images)

G4 solar storm watch

The National Oceanic and Atmospheric Administration upgraded a geomagnetic solar storm watch from a Level 3 ("moderate") to a Level 4 ("severe") watch after several solar flares combined.

According to NOAA, the explosive acceleration of charged and superheated plasma, known as a coronal mass ejection or CME, speeds through space and expands.

Check back for more updates. The Associated Press contributed.