From SWPC:

Space Weather Message Code: WARSUD
Serial Number: 95
Issue Time: 2011 Nov 28 2131 UTC

WARNING: Geomagnetic Sudden Impulse expected
Valid From: 2011 Nov 28 2150 UTC
Valid To: 2011 Nov 28 2220 UTC
IP Shock Passage Observed: 2011 Nov 28 2115 UTC

If you look here at the Canadian magnetometer chain operated by the Geological Survey of Canada, you can see the arrival at Earth.

Each column is the X/Y/Z and the rows are individual stations by code. +/- 200 NanoTeslas