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By Chris White

Weather Blog: Since Fredericksburg resides "in the seam" between the Richmond VA and Washington DC media markets this blog is a look at the weather from a Fredericksburg-centric point of view.

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More light snow this morning, with another Clipper on the way Monday night

This winter has evolved into a string of minor disturbances that zoom through the Fredericksburg area via the jet stream.  The current situation is illustrated in this forecast graphic from the NAM model at the 500 mb (~18,000 feet) level:

This graphic illustrates two features I’ve mentioned before on this blog.  The first is the “long wave trough” circled in white that resides over the East Coast.  This is a southward dip in the jet stream that allows colder air to slide toward the equator and creates the conditions for large surface low pressure systems to spin up, especially on the eastern edge.  A small disturbance along the base of this trough is what is providing this morning’s (Sunday’s) light snow.

The second feature that is plaguing us on a regular basis this winter is illustrated by the feature circled in black over the Canadian prairies.  This is the “short wave trough”, otherwise dubbed as the Alberta Clipper because (a) it forms east of the Canadian Rockies over the province of Alberta and (b) it rides very quickly along the jet stream (hence the Clipper designation).  It is basically a small disturbance superimposed on the larger atmospheric troughs that can create a relatively weak surface low pressure system with limited moisture.  Because of this limited moisture and the rapid movement of the system it usually spits only light accumulations of precipitation over our area.

This next Clipper is projected to affect our weather Monday night although there is some question whether temperatures will be cold enough for rain or snow showers for the ‘Burg.  The morning National Weather Service forecast discussion mentions this:  “ALL AREAS NORTH OF A LINE FROM FROM SOUTHERN CALVERT TO SPOTSY WESTWARD WILL SEE LIGHT SNOW”.  So once again Fredericksburg sits astride the rain/snow line, something we should be used to by now.

To recap the near term weather the snow showers should end this afternoon around the ‘Burg, with clearing skies overnight and a low temperature tomorrow morning in the low 20′s (F).  Then Monday will dawn under mostly sunny skies with a high temperature climbing to near the 40 degree mark before clouds move back in ahead of the oncoming Clipper system.  This quick hitter will be through by dawn Tuesday, and then a relatively slow warmup will take place as high temperatures rise into the low 50′s by Friday.  As I mentioned in the last post the Climate Prediction Center is calling for the first half of February to hold above normal temperatures, so this week looks like the beginning of a warming trend for the ‘Burg.

Enjoy the Super Bowl this evening and stay safe!

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Permalink: http://news.fredericksburg.com/weather/2013/02/03/more-light-snow-this-morning-with-another-clipper-on-the-way-monday-night/