NOAA SWPC issued a G3 or greater geomagnetic storm warning through 10/2359 UTC after a CME arrived on 08 Oct at around 10/1434 UTC. The notice puts geomagnetic storm aurora visibility in the northern US in focus for the active warning window.
The warning means the geomagnetic field reached G3 levels beginning at 10/1758 UTC and was expected to stay at or near that level through 10/2359 UTC. NOAA listed the notice through its Space Weather Prediction Center, part of the National Oceanic and Atmospheric Administration.
NOAA Space Weather Prediction Center
The Space Weather Prediction Center is the source of the warning, and the notice ties the change to the arrival of a CME. That sequence matters because the warning is not open-ended: it runs on a defined UTC window, with the elevated conditions already observed by 10/1758 UTC.
The center is listed at 325 Broadway, Boulder CO 80305. That address identifies where the warning was issued from, but the notice itself stays centered on the storm level and timing rather than on a broader forecast narrative.
G3 warning window
A G3 designation is the specific threshold named in the notice, and the warning remains valid only through 10/2359 UTC. For readers watching for aurora conditions, the practical point is the time box: the storm level had already been reached, and the elevated period was still expected to continue within that same UTC span.
The notice does not assign any specific state or city for visibility. That leaves the warning precise on severity and duration, but not on where aurora visibility would actually occur during the active period.
08 Oct CME arrival
The timeline in the notice starts with the CME arrival on 08 Oct at around 10/1434 UTC, then moves to the geomagnetic field reaching G3 levels at 10/1758 UTC. From there, NOAA SWPC said the stronger activity was expected to persist at or near G3 levels through 10/2359 UTC.
For a reader tracking the sky, the actionable part is simple: the window was already active, and the warning stayed tied to a specific end time. Which areas, if any, were expected to see auroras during the warning period?
