Saturday, October 11, 2014

Threat of Severe Weather on Monday

The atmosphere has been unsettled over the Mid-South for the last several days, with continued rain and thunderstorm chances as a frontal boundary has meandered across the region. This front passed through the metro area Friday night, leaving behind much cooler temperatures and occasional showers Saturday. However, it will lift back north Saturday night, as a warm front, putting the Mid-South back into the warmer, muggier, and more unstable airmass. While a chance of showers and t'storms exists Sunday, the best chances will arrive Monday as a powerful surface and upper-level system takes shape across the Plains states. This will set the stage for what increasingly looks like a severe weather event for the Mid-South Monday afternoon and evening.

Thunderstorms are likely to begin organizing over Central and Western Arkansas Monday morning ahead of a cold front pushing eastward through the state. A strong low pressure system in Missouri will travel northeast during the day, dragging the cold front into the Mid-South This should push what will become an extensive line of thunderstorms into the metro area sometime between Monday afternoon and early evening. With the timing of storms currently expected at what we call "peak heating", the amount of instability in place should be maximized and sufficient for severe weather. This is especially true considering this system will carry a high amount of wind energy (or wind shear) aloft, which combined with the instability will aid the line of storms to become well organized and sustained, and more easily able to transfer those high wind speeds aloft to the surface.
GFS model forecast at 4 PM Monday, October 13, depicts a line of strong to severe thunderstorms entering
the Memphis metro area at that time.
In anticipation of this threat, the Storm Prediction Center has outlooked a large area under a "Slight Risk" of severe thunderstorms for Monday, with the entire Memphis metro area centered on an enhanced 30% probability of severe weather expected within 25 miles of a given point. At this time, the greatest severe weather risk is expected to be damaging wind, which could be rather widespread along the line of storms. However, with the amount of wind energy and instability forecast, a risk of a few tornadoes developing within the line is likely to be present as well. A risk of hail cannot be ruled out, but is lower. Additionally, torrential rain falling in a short amount of time could create some flash flooding issues. The threat should end by early evening as the cold front exits the region, but look for more specific timing and threat details Sunday as computer models continue to come into better agreement. Behind this system, a return to cooler temperatures and drier weather is expected.
Storm Prediction Center Day 3 Convective Outlook valid for Monday. The entire metro area is outlooked
in a 30% probability of severe weather within 25 miles of a given point.
With the chance of severe storms increasing, we highly recommend you check the settings on StormWatch+ in your app to be sure you will be alerted to any weather alerts that may be issued Monday. If you don't have the MWN app for Android for iPhone/iPad, or haven't upgraded to add the precision warning technology of StormWatch+, links below will provide more information. Also, now is a good time to review your severe weather safety and preparedness plans so you know where to go and what to do if severe weather threatens your area.

Kevin Terry, MWN

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