A powerful solar storm developed in the earth's magnetic field shortly before 10 a.m. Tuesday, and it could have visible effects tonight in the Philadelphia region.

On a scale of 9, the Space Weather Prediction Center tonight indicated a "Kp Index" of 8 -- that's an estimate of the extent of the aurora -- meaning the northern lights would be visible as far south as Washington.

That's stronger than earlier forecast, and Bob Rutledge, a space-center scientist, said this afteroon that it's "very possible" that the aurora will be visible in the Philadelphia region tonight.

"It's as good as chance as any in the last few years, and maybe even in the years to come," said Rutledge. He added that it is difficult to forecast just how long the aurora would be visible.

The source of the potential light shows consists of two "coronal mass ejections," or CMEs, each carrying perhaps a billion tons of plasma from the sun, that left the sun on Sunday, appropriately.

They arrived about 10 a.m. at the earth's magnetic field, touching off a potent geomagnetic storm, rated a G4.

Given the recent lull in solar activity, that is one of the more-potent recent storms, Rutledge said.

This disturbance could end up affecting some radio transmissions, with a remote chance that it would impact some power grids, Rutledge said.

Aesthetically, however, geomagnetic storms can create visual bonanzas in the night sky, decorating it with elegant curtains of subtly colored lights.

Meanwhile, closer to Earth, some computer models are hinting at the potential for a snowstorm in time for the equinox in these parts

The most important thing to keep in mind in that regard is that it's only Tuesday.

Let's root for the light show.