Furnace was over heating, and the high temp limit switch would shut down the furnace in cold weather.
Shane, the excellent tech and I discussed how a dirty furnace filter, in combination with the original install: where the furnace gas flow-rate hadn't been de-rated for this elevation. So he reduced the natural gas rate going into the furnace and bumped up the RPM on the blower fan. We discussed many different options to reduce allergens; as well as, more home owner cost saving options. I highly recommend Caliber for their valuable services.