EagleTribune.com, North Andover, MA

Merrimack Valley

January 22, 2013

'Trough' storm drops varying snowfalls

Messy a.m. commute expected across region

A slow and slippery commute was predicted this morning as a unusual weather system was expected to dump from 3 to 8 inches of snow across the region.

“This is one of the toughest forecasts in a long time,” said Ryan Breton, an ardent local weather observer and a meteorology major at Penn State University.

In the Merrimack Valley and southern New Hampshire, a 20- to 25-mile storm band known as a “Norlun Trough” was expected to blanket the area with varying levels of snow, Breton said.

The Norlun Trough is unique because it leaves varying amounts of snowfall within a small geographic area. This condition is also marked by rapid snowfall each hour, according to meteorologists.

“Most of the Merrimack Valley will see 3 to 6 inches of snow by tomorrow morning. And there’s the outside chance of 6 to 8 inches in a few spots,” Breton said.

The Norlun Trough weather pattern was discovered in 1992 by two meteorologists, said Breton, who runs the local website Atkinsonweather.com. Atkinson, N.H. is Breton’s hometown.

The morning drive might be tough, but afternoon commuters should fare better. The bulk of the storm should be over by 11 a.m., said Breton, a 2012 graduate of Central Catholic High School in Lawrence.

The National Weather Service also issued a winter storm warning until 1 p.m. today.

In forecasts posted last night, NWS predicted 6 to 9 inches of snow in the Lawrence area. Snow fall could accumulate at 2 inches per hour with visibility at less than one-fourth of a mile, wind gusts up to 40 mph and temperatures in the low 20s.

The National Weather Service was also anticipating travel problems this morning with “travel slow at best on well treated surfaces and quite difficult on unplowed and untreated” roads.

Tomorrow, a blast of Arctic air is expected to bring frigid weather to the region.

Follow staff reporter Jill Harmacinski on Twitter under the screenname EagleTribJill.

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