Northern lights forecast September 21
Updated: Sep 23, 2019
Tonight can go both ways, I am expecting decent northern lights activity. we have good parts with no low level and mid-level clouds however we still have the high-level clouds. but according to the cloud forecast, high-level clouds could vanish after midnight. I did see some gaps already through the high clouds so they aren't as thick on parts as last few days.
I would go out but with that in mind there is big chance of only seeing clouds, but if you find parts to the north horizon that you can see stars you would probably see the lights as well. its a risk with a reward, as cloud forecasts aren't always 100 accurate. You would need to read the clouds a bit of low and mid-level clouds at locations they should not be, there is always a chance 30 minutes drive in any direction with no clouds.
I would imagine tour operators to both cancel and go as it can easily be just clouds, but with no chance last few days and cloud on the forecast for the coming days, I would assume some of them would go and test there luck tonight. Given you and them go, my guess is the best time is after midnight even until 2 in the morning.
If you are located in the northeast of Iceland I am assuming you will see the lights from there.
So put some gas on your car, put your hot chocolate in a thermos and drive North from Reykjavik towards Hvalfjörður or Borgarfjörður, and stick around with your eyes on the sky. If no low-level clouds at Grimsnes area the high cloud should disapera from there, but there is higher chance of low-level clouds, if in the area I would take a look.
Cloud cover forecast
further reading on the clouds:
https://www.vedur.is/vedur/spar/skyjahula/#teg=skyjahula just a note, there will be an updated on the cloud forecast at 18:00-21:00 and midnight.
Geomagnetic observation and KP Index
KP index forecast is at 2, which is good for Iceland. and I am guessing the local k index will be higher with short bursts a few times after dark.
This graph shows the local K index at Kiruna Sweden and is rather accurate for Iceland as well.
this linear graph is a geomagnetic observation meter located in Reykjavik, its not as detailed as the Swedish one but still a good one. it has about 15 minutes latency from what you see if standing out in the night until the line drops on the graph. so it's better to be already out as if you stay at home and wait for the line to drop and see it drop on the graph and then drive out you might have already missed the action. minor movements during the day is a really good sign of the line to drop 1 - 2 times after dark.
further observation on Lerivogur meter
the black spot just right of the center of the sun is a coronal hole and this could produce strong solar wind that will rattle the earth atmosphere and bring particles from the sun that create the northern lights, I am expecting this to arrive tonight.