Is it too late? I just finished making a magloop for HF. Is there a particular characteristic you can detect of the solar flare with a HF antenna?
Signals go away, and when they are really bad the normal band noise (not caused by power lines or other strong local noise sources) will actually go down in amplitude.
Sometimes AM broadcast stations will be attenuated.
The effects are not seen during the night hours, however the disturbance caused by a CME can be very disruptive during both night and day.