Monday, May 13, 2013

Weekend Severe Weather Threat Could Be Significant

It's looking more and more like this weekend could hold a potentially significant severe weather event for portions of the country.

Situation begins unfolding with a storm system digging into the central Plains Saturday afternoon. 500mb vorticity values from the latest GFS model indicate that the event should begin in Nebraska, Kansas and possibly into Oklahoma. Current indications are that this event will be the beginning of a multi-day severe weather event. This Saturday portion appears to be aligned with a damaging wind and hail threat, with the tornado threat sitting in the background. Storm system will be pushing into the Plains getting ready to go towards a negative tilt, which should happen on Sunday.

Instability parameters for Saturday are impressive across the Plains, with as much as 4000 j/kg of capped instability spread across the western portions of Kansas and Nebraska. Capping inversion is certainly a concern with this event, especially on Saturday, but as the storm begins to get a negative tilt we should see instability increase and the risk of nasty storms increase as well.

Sunday becomes a much more significant day in my opinion, as the storm system begins to dig hard and achieve a negative tilt in the process. Significant vorticity lobes are draped across the Plains and Upper Midwest along the sharp height gradient between storm and ridge. This gradient appears to be centered in the Midwest, and it is here where we may see the strongest storms of the day hit. Cities like the Quad Cities in Iowa, Chicago and Rockford in Illinois, and Milwaukee and Madison in Wisconsin may see some nasty weather on Sunday. Instability parameters show over 5000 j/kg of instability overnight Saturday, decreasing into the mid-3000's by evening on Sunday.

When the trough begins to tilt negatively, it looks like the storm formation style will shift towards a more linear system. My gut tells me we'll see either a squall line or at least some form of linear convective system that moves through the Midwest. I find it hard to believe the environment presented by the GFS above supports an individual cell-type storm over a linear storm system.

Another thing to be watchful of is the massive amount of moisture that will be flooding the Plains and everyone on eastward. With the quantity of moisture that will be present in the United States as the severe weather event blows through, I would bet on at least a marginal flooding risk evolving across portions of the nation over the weekend and into the beginning of next workweek. Now, we're a while out from this event, so I can't get into the depth or expanse of this flooding potential, but when you have this amount of moisture just waiting to be converted to rain, it's easy to find a little flooding potential that could escalate quickly.

As of the current time, my map for this multi-day event is below.