NOAA forecasters have issued a watch for minor-to-moderate geomagnetic storms May 16-17. Forecasters say there is a 40% chance of minor (G1) geomagnetic storming on May 16, as Earth enters a stream of solar wind flowing from a hole in the Sun’s atmosphere. The storm could intensify to moderate (G2) on May 17, due to a combination of coronal hole activity on the Sun’s surface and the impending arrival of a May 13 coronal mass ejection (CME), which is expected to deliver a glancing blow to Earth’s magnetic field.

The storming could make auroral displays visible at lower-than-typical latitudes. Under G1 and G2 conditions, HF radio propagation can fade at higher latitudes.