NOAA’s Space Weather Prediction Center (SWPC) issued a G2 – Moderate geomagnetic storm watch, forecasting the arrival of a coronal mass ejection (CME) at Earth on March 19.
Geomagnetic activity is expected to remain below G1 levels on March 18, intensify to G2 on March 19, and weaken back to G1 conditions on March 20. The bulletin supersedes all previous watches and reflects updated modeling of the CME’s propagation through interplanetary space.
The event is associated with an M2.7 solar flare that erupted at 12:15 UTC on March 16 from Active Region 4392. The flare was accompanied by a Type II radio emission with an estimated shock speed of 1 227 km/s, a Type IV radio emission, and a 10 cm radio burst peaking at 380 sfu.
Coronagraph observations shortly after the eruption revealed an asymmetric halo CME, confirming that at least part of the ejecta is directed toward Earth. Subsequent modeling by SWPC placed the most likely arrival window on March 19.
Impacts from G2 geomagnetic storm conditions are expected primarily poleward of 55° geomagnetic latitude. Under these conditions, power grid fluctuations can occur, and high-latitude power systems may experience voltage alarms. Spacecraft operations may be affected by orientation irregularities, and increased atmospheric drag can impact low Earth orbit satellites.
High-frequency (HF) radio propagation may degrade at higher latitudes during the storm period, affecting aviation and maritime communications. The effects are typically temporary and confined to geomagnetically active regions.
Auroral activity is expected to intensify during the peak of the storm on March 19, with visibility potentially extending significantly equatorward. Under favorable conditions, aurora may be observed as far south as New York, Wisconsin, and Washington state.
References:
1 Forecast Discussion – NOAA/SWPC – Issued at 12:30 UTC on March 17, 2026