This morning's time series from Mt. Baldy, located at the top of Little Cottonwood Canyon, shows that temperatures have climbed for a nearly 24 hour period. They have climbed at night and during a period when the flow was consistently out of the northwest.
Further, these increasing temperatures have occurred during a period of weak or perhaps even slightly negative temperature advection at 700 hPa.
The 1200 UTC sounding also shows winds that back marginally with height, consistent with weak cold advection.
So what gives? In this instance, the warming is related to vertical advection rather than horizontal advection. Check out the 0000 UTC sounding and you can clearly see the stable layer that was located just above crest level and which is now much lower, yielding the warmer temperatures on Mt. Baldy.
This provides a nice example of how one needs to think of advection as a three-dimensional process. Further, it is a nice event leading into PCAPS of how large-scale processes can isolate a pocket of stable air in the valley.