The GFS forecast loop below shows the development of the cyclone off the Pacific Northwest coast. It forms along the pre-existing warm front associated with a parent cyclone south of the Aleutian Islands as an upper-level trough (indicated by color fill) approaches from the west.
|GFS forecast loop of sea level pressure (black contours), 925 mb temperature (red contours), and dynamic tropopause pressure (color fill)|
The GFS analysis wins no beauty contests, but it shows two key features associated with intense marine cyclones. The first is a warm-core seclusion — a pocket of warm air surrounded by cooler air that is roughly colocated with the low center. The second is a bent-back front — an extension of the warm or occluded frontal zone into the cooler airsteam behind the low.
Paraphrasing a wise Norwegian meteorologist, "beware of the poisonous tail of the bent-back front." The cyclone reaches maximum intensity right at landfall when it features a very intense inner-core pressure gradient. This is a scenario for producing very strong winds. Indeed the Eureka National Weather Service forecast office has hoisted just about every non-convective warning you can possibly imagine for their county warning area. The Oregon coast will also see impacts from this storm, especially the southwest coast should the low take a northerly track.
So, pardon my digression from the developing snowstorm over northern Utah. No promises, but perhaps there will be another post later.