An unusually strong solar storm headed toward Earth could produce northern lights in the U.S. and potentially disrupt communications this weekend.

An unusually strong solar storm headed toward Earth could produce northern lights in the U.S. and potentially disrupt communications this weekend.

The National Oceanic and Atmospheric Administration issued a rare geomagnetic storm watch — the first in nearly 20 years. The watch starts Friday and lasts all weekend.

NOAA is calling this an unusual event, pointing out that the flares seem to be associated with a sunspot that’s 16 times the diameter of Earth. An extreme geomagnetic storm in 2003 took out power in Sweden and damaged power transformers in South Africa.

The latest storm could produce northern lights as far south in the U.S. as Alabama and Northern California, according to NOAA.