Forecasters are tracking a geomagnetic storm threat after an M2. 7 solar flare on March 16 launched a coronal mass ejection (CME) toward Earth, and space weather centers have issued watches for the nights ahead.
What Happens When a Geomagnetic Storm Arrives?
The eruption launched on March 16 expanded away from the Sun and is now en route to Earth. Satellite imagery and model runs show the CME’s transit, and an arrival in the overnight window around March 19 is the focus of current forecasts. NOAA’s Space Weather Prediction Center has issued a G2 (moderate) geomagnetic storm watch for the early hours of March 19 ET, with G1 (minor) conditions anticipated to begin around 11: 00 p. m. EDT through 2: 00 a. m. EDT, followed by G2 conditions from 2: 00 a. m. through 8: 00 a. m. EDT.
When the CME impacts, it will disturb Earth’s magnetic field and can push the auroral oval equatorward, producing visible Northern Lights at higher and sometimes mid-latitudes. Model output from NASA’s Solar Dynamics Observatory and ENLIL simulations place a likely arrival around 12: 00 UTC on March 19, but timing remains uncertain and could shift earlier or later. Cloud cover will determine whether observers catch the show.
- Likely timing windows (ET): G1 around 11: 00 p. m. through 2: 00 a. m.; G2 from 2: 00 a. m. to 8: 00 a. m.
- Canadian regions with clearer skies in current forecasts: Northwestern Ontario; a band across eastern New Brunswick, Prince Edward Island, and western mainland Nova Scotia; in the west, southern Manitoba, southwestern Saskatchewan, southern Alberta, and interior and central British Columbia.
- Possible reach: G2 could bring aurora as far south as New York and Idaho; there is a chance of G3 conditions that could allow sightings into mid-latitudes such as Illinois and Oregon.
- Visibility caveat: If the main CME arrives during daylight hours at a given longitude, observers could miss the display.
What If the Multiple CMEs Extend Activity?
Forecasters now note that at least four CMEs may be headed toward Earth in quick succession. That pattern can complicate timing and intensity: rather than a single, short-lived peak, geomagnetic activity could persist for 24–48 hours or longer. Some model runs suggest the primary CME could arrive later, and ensemble outputs point to the possibility of activity extending into March 20–21 ET and beyond, potentially producing multiple nights of auroral displays at lower latitudes.
Extended activity raises two practical outcomes. First, observers at mid-latitudes should be prepared for intermittent displays over several nights rather than a single blackout window. Second, forecasting uncertainty increases; overlapping CMEs can amplify or weaken combined effects depending on magnetic orientation and arrival spacing. The result is a forecasting window that favors vigilance rather than certainty.
What to expect in the short term: watch timing windows around late evening and the early morning hours in ET, monitor local sky conditions, and be aware that activity could start sooner, peak later, or stretch across multiple nights. The situation remains fluid, but the approaching solar eruptions present a clear chance of auroras and magnetospheric disturbance linked to the current geomagnetic storm
