[CQ-Contest] Scandanvian propagation question

[John Geiger]

Something I have noticed during the ARRL DX contest, and other winter
contests, as well as during casual DXing, maybe a LA/SM/OH contester will
have a better explanation for this:

This past Friday I worked a SM3 on 15m FT8 at 5:15pm local time (2315 UTC),
well past the time that the path to Europe on 15 had closed.  This isn't
the first time I have had this occur.  Over the past few years I have
witnessed this before, stations from LA/SM/OH coming through on 15 and 17
meters mid to late afternoon, several hours after the path to Europe had
closed for that band.  They haven't been coming in the whole time since the
disappearance of the rest of Europe, it is like a new path opens up several
hours later, but only to these regions.  These areas in Europe will have
been in darkness for several hours as well, dropping the MUF below 15 and
17 meters, but there they are.

This is a winter phenomena I am discussing.  I am very familiar with Europe
coming in later at night on 15 and 17 during the summer months, especially
during higher sunspot numbers.

So does anyone know of the propagation mechanism to explain this-why this
one part of Europe comes in several hours after the path to the rest of
Europe has closed-and when it is well into darkness at their QTH?  I am
guessing it might have something to do with their location in the Auroral
Zone and some sort of Aurora to F2 hookup, but that is just a guess.

73 John AF5CC