Ever since I've watched the sun, it's done nothing but let me down. The current solar cycle has been the weakest in over a century, so when we have a coronal mass ejection aimed directly at Earth, I get excited.
Most likely nothing besides lower-latitude aurora will result from this, but I'm hoping for the worst. After all, the space science community could use some funding.
Expect the arrival around 2000 UTC this Saturday (9/13/2014).
I'd wager around 36 hours. It's hard to say for sure, depends on the properties of the plasma cloud; density, speed, and magnetic field orientation. Here's my favorite model. They're expecting it earlier than I've predicted, and if the interplanetary magnetic field is oriented northward, like they're showing, the conditions aren't ripe for magnetic reconnection, which severely diminishes the amount of geomagnetic storming. Still, our magnetosphere will constrict from the force of the impact, which will give us a significant substorm, if nothing else.
The latter. We can't really "see" the plasma in between the time it leaves the corona and arrives here. One of our best tools is the ACE spacecraft, which orbits around Lagrangian Point 1, about an hour upstream of us (under typical solar wind speed conditions). For a storm, we'll see it coming about 20 minutes before it hits the magnetosphere, but then it takes about another hour to propagate back through the magnetotail and send ions slamming down into the polar atmosphere... then voila, aurora.
Update: my prediction time was far too late, as the CME has just swept past the ACE spacecraft about 2 hours ago (~1530 UTC, 9/12/2014). Really great to watch this unfold in real-time on that aggregated data site, solarham.com. Definitely the strongest event I've ever caught "live". Expect some nice Aurora tonight, especially in Northern Europe and northeast to north-central North America. Hopefully they're still around by the time Alaska rotates past the terminator line.
Hey if you want to see a good map of Aurora activity, you can use http://www.gi.alaska.edu/AuroraForecast which draws a predicted map of the Aurora based on previous data.
I'd be very surprised if they made it lower than 45 degrees.