Update: G3 (Strong) or greater warning issued until 1200 UTC on 20 September

The 18 Sep CME began impacting the geomagnetic field at 20/0605 UTC (2:05 AM ET).  We were currently running at G1 (Minor) geomagnetic storm levels just before the CME arrived.  We have issued a G2 (Moderate) geomagnetic storm warning through 1300 UTC.  A G3 (Strong) or greater geomagnetic storm warning was issued until 1200 UTC today.  We are currently running close to G3 levels as of 0740 UTC today.  Stay tuned to www.swpc.noaa.gov for further updates as the CME effects unfold over the next few hours.