Friday, December 21, 2012

December 24-25 Clipper System

**This post is dedicated to Ana Marquez-Greene, age 6, a victim of the Connecticut shootings.**

It is becoming increasingly likely that a small clipper system will deliver precipitation and disturbed weather to the Plains and Midwest during Christmas Eve and the day of Christmas.

Above is the NAM model forecast, valid for the afternoon of Christmas Eve. We see a small, negatively tilted area of vorticity in the upper left hand part of the collage of images above. The system looks to be a clipper, pushing to the southeast from Canada. It's lack of sustained moisture and unimpressive isobar gradient tells me this will not be a winter storm event at all. 6 hour precipitation values in the upper right tell of light snow ongoing in the Upper Midwest in response to this system. High pressure stationed in the Plains will provide a base for cold air in the region.

Two forecasts, both based off of the NAM model but known as parallels (slightly changed from the NAM model itself), show 3 hour snow in north Wisconsin and Minnesota during this system as light, nothing extremely impressive. Based on the low prospect for any big accumulating snows, and the NAM's lack of moisture in the top image collage, this does not look like anything to get excited about. If you're into the traditional snowing on Christmas Morning, those in the West Great Lakes may have a shot at such a prospect as the clipper continues pushing to the southeast.


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