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Strong to Severe Storms in the Upper Midwest; Bering Sea Low Continues to Impact Southwest Alaska

Scattered severe thunderstorms are possible Thursday across central and eastern Minnesota, Iowa, and western Wisconsin. A few tornadoes, isolated very large hail, and damaging winds may occur. In southwest Alaska, a Bering Sea low continues to cause strong winds, significant rainfall, and high seas, with further impacts expected Friday into the weekend from a North Pacific storm. Read More >

Overview

On the morning of April 14th, a strong low pressure system was tracking northeastward across the Mississippi River Valley. The associated (nearly stationary) warm front was just to the north of our CWA, with both temperatures/dewpoints already in the 60s across the area. The low quickly tracked to the northeast during the day on the 14th, as our CWA stayed in the warm sector. Isolated to scattered thunderstorms formed over parts of the central/western CWA during the afternoon on the 14th. No severe weather occurred over our area during the day on the 14th, but there were a few damaging wind reports over western VA.

A quasi-linear convective system (QLCS) developed from Ohio southward to WV during the afternoon of the 14th ahead of the trailing cold front. As the surface low tracked northeast into New York by the early morning hours of the 15th, the QLCS had become more of a broken line as it was about to enter the CWA from the west (see 04z surface/radar map in the Environment Section). Despite the fact that it was just past midnight, temperatures were still in the low-mid 70s across the area with strong S winds. Coupled with dewpoints in the mid 60s-near 70 F, this allowed for the QLCS to strengthen (and still be largely surface based) as it tracked eastward across our CWA during the early morning hours of the 15th. A 50-65 kt southwesterly 925 mb jet was centered over the eastern half of the CWA by 2 AM (06z) on 4/15 as the line approached. Even though surface winds were largely out of the south (and not SSE-SE), 0-1 km SRH values approached 400 m2/s2 in spots. As a result, several mesovorticies were observed along the leading edge of the QLCS as it tracked over central and eastern parts of the area. A couple of these ended up producing brief EF-0 tornadoes; one was in the northeastern part of Dorchester County, MD and the other was near Heathsville, VA. Elsewhere (especially east), there were numerous wind damage reports (as well as a few gusts of around 70 MPH). The fact that these storms were surface-based (coupled with a strong 925 mb jet) likely allowed for the QLCS to produce quite a bit of wind damage across the area before it quickly moved offshore after 5 AM.

See the Environment section for more details regarding specific severe weather parameters. In the Radar section, see a close-up image of the storm that produced a tornado in Dorchester County, MD. 

***Please note that this data is preliminary and is subject to change***

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