NOAA forecasters see G1 storming likely on November 17 as a November 14 eruption may graze Earth

NOAA's Space Weather Prediction Center sees a minor geomagnetic storm as likely on November 17, and it now gives an extra reason. In its three-day forecast issued at 12:30 UTC on November 15, 2026, the center said G1 (minor) storm levels are likely that day as a high-speed solar wind stream from a coronal hole moves into a position to affect Earth, "coupled with the possible arrival of the 14 Nov CME late in the period." That coronal mass ejection, or CME, is new since the center's November 9 outlook, which had already marked November 17 and 18 as likely G1 days, as our November 12 report described. All times here are UTC, as the center gives them.

What left the Sun on November 14

The center's forecast discussion traces the CME to a C2.8 flare at 21:27 UTC on November 14 in Region 4579, a sunspot group it places at N15E66, 15 degrees north and 66 degrees east on the solar disk. By our reading of those coordinates, that is well toward the Sun's eastern edge as seen from Earth. The flare came with Type II and Type IV radio bursts, and the center's alert for the Type II burst gave an estimated velocity of 1,972 kilometers per second.

The cloud first appeared at about 21:36 UTC in images from LASCO, the coronagraph on the Solar and Heliospheric Observatory (SOHO), which the center describes as its primary means of analyzing and categorizing CMEs. Modeling and analysis indicate "possible glancing influences late on 17 to early 18 Nov," the discussion says. Earlier the same day, from about 01:30 to 09:30 UTC, a large filament lifted off the Sun's southern hemisphere, but forecasters found no CME from it in the coronagraph images available to them.

The forecast, three hours at a time

Only one block carries the G1 label: 03:00 to 06:00 UTC on November 17, at 4.67. By our reading, that block comes before the CME's modeled window, late on November 17 to early November 18, which the table only partly covers. The other blocks on November 16 and 17 range from 2.00 to 3.67, by our reading of the table, and the largest Kp observed in the 24 hours before the forecast was 2. The center expects mostly quiet conditions on November 15, unsettled to isolated active periods on November 16 and active periods with isolated G1 levels on November 17. The solar wind slowed from about 430 to about 365 kilometers per second over the past day, and forecasters say a gradual increase in solar wind parameters is likely on November 16, ahead of the coronal hole stream.

The G1 block, 03:00 to 06:00 UTC, is 10 p.m. to 1 a.m. Eastern Standard Time on the night of November 16-17, by our conversion. That is also the peak night of the Leonid meteor shower, as our late November sky guide explains.

What a G1 storm means

On NOAA's five-step scale, G1 corresponds to Kp 5. At that level, the scale says, weak power grid fluctuations can occur, a minor impact on satellite operations is possible, and aurora is "commonly visible at high latitudes (northern Michigan and Maine)."

CMEs are large expulsions of plasma and magnetic field from the Sun's corona, according to the center's explainer. They travel at anything from under 250 to nearly 3,000 kilometers per second, so the fastest Earth-directed ones can arrive in 15 to 18 hours and slower ones take several days. Stronger storms are favored when the magnetic field a CME carries points south for a longer, more pronounced stretch, the center says, and most CMEs show changing field directions as they pass Earth.

The center's geomagnetic storm watches give the highest storm level it predicts for each day. When we last checked its list of alerts, watches and warnings, at 13:09 UTC on November 15, the newest geomagnetic storm watch dated from November 7 and covered November 7 to 9; none covered the days ahead.

Flares and radiation

Solar activity was low in the 24 hours before the forecast, with low-level C-class flares, and the center sees a chance of M-class flares strong enough for minor to moderate radio blackouts, R1 to R2, putting the odds at 25% on each day from November 15 to 17 and at 5% for R3 or greater. It expects no solar radiation storm, giving S1 or greater a 5% chance each day. The flux of electrons with energies above 2 MeV is high: it peaked at 5,837 pfu (particle flux units) at 13:00 UTC on November 14, under an alert that has run since 22:45 UTC on November 8, and is expected to stay high through November 16 before easing to moderate levels on November 17.