Tuesday, February 21, 2012

This Is a Dirty Ridge

Go ahead, make my day.
Source: wikipedia.org
With a ridge to our west this morning, one would normally expect nice weather.  That's conventional wisdom, but some ridges are dirty.  A dirty ridge is typically low in amplitude, enabling moisture, clouds, and precipitation to spill over to its downstream side, especially when a short-wave trough moves downstream of the ridge axis.

In addition, the ridge presently to our west has a nice connection to the subtropics on its upstream side.  As a result, there is a plume of subtropical moisture originating to the northwest of Hawaii that is spilling over the ridge axis into the Pacific Northwest. 
1500 UTC 21 Feb 2012 IR satellite image and GFS analysis of precipitable
water (contours every 5 mm) and 925 mb wind (vectors).
This should yield a couple of days of cloudy weather with some periods snow in the Wasatch Range. Precipitation will be greater, however, further to the north which will be more directly in the moisture plume.
This is also a scenario that could bring some rime and strong winds to the Wasatch.  Bottom line is to be prepared for just about anything if you will be in the mountains today, tomorrow, or Wednesday.  

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