Tuesday, April 19, 2011
Tornado Watch issued - Tuesday evening severe weather update
A Tornado Watch has been issued for all of east Arkansas, extreme western TN, and extreme northwest MS until 2am Wednesday (see the map above, pink areas). Atmospheric parameters are coming together for a likely severe weather event during the overnight hours tonight. Severe storms require a few ingredients, including a source of lift (in this case a fairly strong cold front), instability (which is plentiful), available moisture (dewpoints are running in the mid 60s) and wind shear (which will be moderate during the event) among a few of them.
Storm threats this evening to our west and north include tornadoes, but as individual supercell and clusters of cells move east, they will evolve into a quasi-linear convective system, or squall line. The associated severe weather threats are expected to evolve as well - towards damaging straight-line wind and large hail. This squall line will be moving to the east at about 30 mph, while storms within the line will be moving very quickly to the NE at 50-60 mph. Given this motion, I expect to see the line move through the immediate metro area between 10pm-2am. Storms in the line will contain very heavy rain and dangerous lightning, and could also contain very large hail, high wind, or an isolated tornado.
MWN will nowcast this event until the line moves east of the metro area or is deemed to no longer be severe. Please review our severe weather coverage policy (PDF). The MWN Storm Center will have the latest severe weather information for the Mid-South. We'll also be signing folks up for our severe weather e-mail alerts this evening. You can sign up by clicking here. Regular updates will take place on our Facebook and Twitter feeds, which you can find links to below. Also, Twitter users can follow @shelbyalerts for automated severe weather watches and warnings for Shelby County, as they are issued by the NWS.
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