"If NOAA's right, and the ensuing geomagnetic storm is minor, it's no big deal. It means the high latitudes could be treated to some brilliant auroras over the weekend with few, if any, negative effects on earth-orbiting satellites or the power grid. On the other hand, if NASA's right, and the geomagnetic storm is strong to severe, Earth-orbiting satellites could get disoriented and the electrical grid, according to NOAA, could experience "widespread voltage control problems" among other issues. Aurora could be seen as far south as Alabama and northern California."
Keith's note: As for who has more accurate information: Well, NASA has something that NOAA does not: a goofy official mascot for the Solar Dynamics Observatory - a rubberized version of a chicken corpse in a NASA flight suit named "Camilla" (identical to what you see in a slaughterhouse) who often tweets odd things such as:
this: "After two Slurpees I always get sphenopalatine ganglioneuralgia - which is actually a fascinating sensation." ; this: "Timmy - how about we go to the Milano Fashion Week together? We'd steal the show!"; This: "Well, real Emmentaler must have holes! The rest of our cheese should not.", and this: "I usually don't take my clothes off until Return of the Jedi... ;-)"
NASA spends money flying this rubber chicken and its handler around - and yet PAO and SMD seem to have little if any contol over what the rubber chicken says. Often times it posts things that NASA PAO or SMD do not post - so a lot of people are getting their NASA space weather news from a dead chicken. Maybe this is why there is some difference between NOAA and NASA. If this is how an official NASA mission mascot spends scarce agency resources then I think I will take my space weather advice from NOAA - they are poultry-free.
Solar activity alerts are available on Twitter via @spaceweather.