Outlier stations are what I call USHCN stations where the data is wildly different from the majority of climate stations. I don't know why this is, but I don't use them when looking at trends. It is definitely not always the UHI
Looking at all of the US it is clear that there is a regional climate change, that doesn't seem to fit the Bruckner cycles. Speaking of, out of all the USHCN stations, only Dale Enterprise shows clear cycles when using Tmin data, which is very cool, and I have found no publications online that mention it.