Wednesday, January 22, 2014

The Clippers Keep On Comin'

Map showing general path of an Alberta Clipper
Credit:  NOAA
A series of fast-moving low pressure systems have brought surges of bone-chilling Arctic air and mostly light snow to the Midwest and east the past week to ten days. These storms, known as "Alberta Clippers", generally develop on the east side of the Canadian Rockies. Typically there is an upper level trough over the eastern U.S. and these storms ride the jet stream southeastward on the back side of the trough.  They are speedy systems and usually are not very intense. Their fast movement also doesn't allow time for a large amount of moisture to be drawn in to the system and results in generally light precipitation. However, much colder and windy weather typically follow these systems.  The strong, cold winds often result in heavy lake-effect snow in the lee of the Great Lakes. Occasionally a clipper will intensify when it reaches the mid-Atlantic Coast and becomes a much stronger storm, such as the one the affected the eastern U.S. last night and today.

48-hour snowfall ending the morning of January 22, 2014.

There have been several of these Alberta Clippers over the past week or more.  The upper level disturbances produce these clippers have been favored by the strong, persistent upper level trough over the eastern U.S. coupled with the ridge in the eastern Pacific.

Here is the 500 millibar map (~18,000 ft) from this morning with three "short waves" marked. Below that is the surface weather map from this afternoon at 1:00 p.m. EST.  The disturbance just off the east coast is associated with the storm that left up to a foot of snow in New York and New Jersey today. The wave over the northern U.S. is associated with the low and cold front moving through the Northern Plains and Midwest today. Further northwest there is yet another wave moving over the top of the ridge that could produce another clipper in a couple of days.

Surface map for 1:00 p.m. EST 1/22/2014

 This animation of the 12:noon CST weather map for the past ten days shows the progression of the Alberta Clippers across the eastern half of the U.S. along the same general path.

Surface weather maps for 12:00 CST January 12-22, 2014

The path of the clippers is also seen in the snowfall pattern over the eastern U.S. the past ten days.

It appears the current upper air pattern will remain in place for the next week to 10 days, so winter weather will continue to affect the Northern Plains, Midwest and east.

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