Sunday, November 17, 2013

High Risk For Severe In Midwest Today, Gusty Winds Here Late Tonight

The Midwest and Great Lakes are going to have a rather late severe weather outbreak (by calendar standards) today. A high risk of severe weather is out for Eastern Illinois and Indiana today, with a moderate risk over a large chunk of the Midwest and Great Lakes. A strong storm system in the Midwest this morning will intensify further, tapping into a robust jet stream aloft and producing thunderstorms that may spawn tornadoes in the Midwest and a "fall squall" of gusty wind and rain eastward into New York and Pennsylvania as the day progresses into night.

We were upgraded within the last hour or so into a slight risk for severe weather, which is for wind only...not for tornadic activity. That stuff stays far to our west.

The severe weather event for the Midwest and Lakes will be at its peak during the afternoon and evening hours as a strong line of storms fires up from near Milwaukee southward into the Ohio Valley, marching east and northeast through the evening hours. Winds could gust to 70 or 75 miles per hour in that line and tornadoes are possible, especially in Indiana and Illinois where the risk parameters for severe are the best.

Because the line's timing brings this towards us after Midnight, the risk for severe weather is low. We shouldn't experience any tornadic development from the fall squall and I don't foresee much in the way of thunder from this line as the low pressure center and the best dynamics push into Canada.  That said, the squall line that eventually develops will have a very robust low level jet with it and will get to feed on that as the night progresses and everything shifts east.

We should get in on the frontal boundary after 4 AM locally -- and it won't be a long duration event tonight either although winds will pick up ahead of the front. We should see south winds increase to near 20 miles per hour in the region overnight ahead of the front, with a two to three hour period of wet weather as the front pushes through.  With the boundary moving through, a brief period of heavier showers is likely and winds may gust to 40-50 miles per hour as it marches on through the region.

The graphic below shows wind barbs at 5000 feet up -- triangles are 50, each full dash is ten additional -- and the graphic shows how the strongest winds with the frontal boundary will again be to our north and northwest as the front moves on in. Winds aloft on the NAM reach 75 miles per hour in Central and Northern Pennsylvania late tonight, 70 mph on the GFS.  Those winds will tap down to the surface and I think we'll see strong wind gusts over 50 mph in these areas. We will have a tougher time getting those level of winds here but I do think 40-50 mph gusts aren't out of the realm of possibility tonight.

40-50 mph gusts are enough to knock a few tree limbs down and perhaps knock out a few power lines. The showers associated with the line aren't modeled to last that long as well -- it's possible we only get a tenth or two tenths of an inch in the rain bucket tonight, if that!

That said, get ready for some gusty winds late tonight in the region as today's high risk in the Great Lakes and its associated front push east tonight in a less robust state.