Whatever was generating the 10/S9 noise on HF is now gone, and in its place signals have returned.

I wonder if something of a wideband, low level noise source just inside my skip zone was effectively propagating into the area. I also wonder if that noise source might have been solar in origin, and with enhanced ionospheric propagation that noise is now being reflected back into space. This would make sense, as the peak of the noise level occurred from roughly 11AM-3PM and the sun's position at that time coincides with the southern major lobe of two of my antennas.