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      2-18-2013: Unorthodox Storm

      The deep low-pressure system should be near the Sault by morning. That means a flow of colder air powered by strong winds over Upper Michigan.

      A broad area of low pressure is gradually getting its act together over the central U.S. and will have a big impact on the weather over most of the Upper Peninsula Tuesday into Tuesday night.

      The system is unorthodox in that itâ??s not a â??Colorado lowâ?? or an â??Alberta Clipper.â?? Itâ??s a system that is gradually getting its act together almost overhead. The initial low formed in western Canada over the weekend. Disturbances have been dropping into a developing upper trough that was over the Plains this morning (Image 1 above). This trough had two low-pressure systems embedded in it; one over northern Minnesota (the weekend low in Canada) and another over southeast Kansas (Image 2). These low are beginning to consolidate into one strong storm, which should be over southeastern Wisconsin early tonight (Image 3). It is forecast to continue to deepen and should be near the Sault by Tuesday morning (Image 4).

      The northern low generated a blizzard in parts of North Dakota and Minnesota. As of late afternoon, the moisture flow into the system was increasing as evidenced by developing rain and thunderstorms from Arkansas northward up the Mississippi Valley to northern Illinois into southern Wisconsin. As this moisture lifts northward, it will change to snow during the night. Right now, it appears that the eastern U.P., closer to the path of the storm, will have the heaviest â??systemâ?? snow late tonight into Tuesday. In general, a 6 to 10-inch snowfall is expected there. The least snow will likely fall over south-central sections from Iron County into Dickinson and Menominee Counties. There, only 1 to 3 inches should fall.

      The expected intensity of the low means strong winds will develop. Look for north to northwesterly winds of 15 to 30 miles per hour with higher winds along Lake Superior. The north-northwest winds means heavy lake enhanced snowfall over northern Upper Michigan. Look for 6 to 10 inches from the spine of the Keweenaw Peninsula southwestward through the high country of Ontonagon and Gogebic Counties. Locally higher amounts are possible through Tuesday night. From Lâ??Anse to Marquette, a general 4 to 8 inches is expected. There will be higher amounts especially west of Lâ??Anse and northwest of Marquette. To the east of Marquette is where the worst conditions are expected. The system snow and lake-effect will mean a general the 6 to 10 with many areas likely to get over a foot. The wind will cause white-out conditions Tuesday on M-28 east of Marquette to Munising and also along the Seney Stretch.