Thanks to two solar flares that occurred in rapid succession late this week, a widespread and potentially vivid display of the Northern Lights is possible for many parts of the U.S. and Canada. This could include parts of the Mid-Atlantic, Midwest, and Pacific Northwest, including cities such as Washington, D.C., St. Louis, Missouri, and Portland, Oregon.
The National Oceanic and Atmospheric Administration (NOAA), which monitors space weather, has issued a G3 or "strong" geomagnetic storm watch for Friday, due to the combined influence of two coronal mass ejections, or CMEs, that were associated with the solar flares.
"The second of the expected coronal mass ejections (CMEs) has arrived, and arrived in good agreement with the predicted arrival times. As expected, an initial look shows this CME is stronger than the first. G2 (Moderate) storming is underway now and the forecast for G3 (Strong) storming on the 13th still looks reasonable," said NOAA's Space Weather Prediction Center on its website on Friday.
Coronal mass ejections, which are essentially magnetic clouds ejected at high velocity from the sun, can affect the electricity grid, radio transmissions and GPS signals, among other things, when they interact with the planet's magnetic field. This event is not expected to cause significant disruptions, and instead could create a significant display of the Northern Lights, also known as the Aurora Borealis.
The Aurora is notoriously difficult to predict, but the best bet for seeing them is to get away from urban lights, and look, well, north, late at night on Friday night into Saturday morning. On Thursday night, when the solar storm was weaker than it will be Friday, the Aurora was observed as far south as New Mexico, based on Twitter reports.
— Reid Wiseman (@astro_reid) September 12, 2014
The Capital Weather Gang blog recommends checking the "K" index, which helps predict Aurora activity, before heading out the door. K indices above a seven typically mean there is a good chance of Northern Lights in the area. As of 6 p.m., the estimated 3-hour Planetary Kp-index was at about a 5.
Another website to look at when planning your Northern Lights spotting is the University of Alaska's Aurora forecasts, although that site was experiencing some hiccups as of 6 p.m. ET.