WASHINGTON (AP) -- An extreme solar flare is blasting its way to Earth and could mess up some power grids, satellites and radio transmissions, scientists say. It's been several years since Earth has had a solar storm of this size coming from sunspots smack in the middle of the sun, said Tom Berger, director of the Space Weather Prediction Center in Boulder, Colorado. Solar storms happen often, especially during peaks in the solar cycle, and don't directly harm people. But what makes this one more worrisome is its location on the sun along with its strength, he said. "There's been a giant magnetic explosion on the sun," Berger said. "Because it's pointed right at us, we'll at least catch some of the cloud" of highly energized and magnetized plasma that can disrupt Earth's magnetic sphere, which sometimes leads to temporary power grid problems. Forecasters don't yet know when Wednesday's solar storm will arrive here and which part of the planet will be facing the sun and bear the brunt of the effects. It could arrive as early as Thursday morning or may take a few days. via News from The Associated Press.