Thursday, November 8, 2012

Intermountain Cyclogenesis

We have an exciting stretch of weather ahead and it starts today with an Intermountain cyclogenesis event.

Cyclogenesis is the formation and development of a cyclone, known colloquially as a low pressure system.  Today we have a nice example of this happening over the Intermountain West.  Watch in the loop below, which includes both analyses from yesterday and last night and forecasts for today, how a cyclone digs southward along the Pacific Coast and decays as a new cyclone forms over the Intermountain West.

This sort of behavior is not uncommon in areas of complex terrain.  Cyclones have a difficult time penetrating through areas of high topography.  As a result, they often decay as they approach a mountain range (in this case, the Cascades and coastal mountains of the Pacific Northwest) and reform in the lee.  The Intermountain West is a favored region for cyclone formation because it lies downstream of the Sierra Nevada and Cascade Ranges.

Also contributing to the Intermountain cyclogenesis event is a frontal zone that pushed into the Intermountain West late yesterday.  The clouds that extend from northern California to Montana early in the loop below are associated with this frontal zone, which helps serve as a locus for the cyclone development.

All of this means that a very strong but slow moving cold front will develop along with the cyclone over Nevada.  The Salt Lake Valley will be ahead of this development cold front today, and experience warm windy weather.  Temperatures will likely reach the low 70s.

The cold front should push into the Salt Lake Valley late tonight or tomorrow morning.  The models still differ on the timing, but tomorrow should eventually feel like you've been transported to another planet as snow levels will be falling all the way to the valley floor.  The difference in temperature between this afternoon and tomorrow afternoon will probably be more than 30F.


  1. Replies
    1. Nevada low = Intermountain cyclone. A.k.a., "Tonopah low."