Severe storms likely early Saturday morning – what to expect

[ Updated at 5:00PM – timing of storms, increasing flooding risk, updated graphics ]

A surface low pressure system with a connecting cold front is situated over north central Texas and southern Oklahoma. This low will deepen and dig toward Arkansas Friday night before it begins lifting out toward the northeast. Most of the models agree that the low will move right up the Mississippi River. This may serve to prolong the period of thunderstorms some, as the line will not move east as fast while the low pressure center is moving parallel to it. 

Detailed outlook for the metro

Thanks to a strong surface high pressure system situated to our east, winds are fairly strong and from the south. In fact, a  Wind Advisory has been posted for the entire area as gusts could reach 25-30 mph this afternoon and 30-40 mph tonight. This will allow abundant moisture from the Gulf of Mexico to reach the Mid-South. With abundant moisture and a strong front to lift the moist air, a line of convective storms will form ahead of the cold front in eastern Texas and propagate through northern Louisiana and Arkansas before crossing the Mississippi River into western Tennessee and Mississippi. The main concern with this event will be the squall line as most models show little in the way of discrete storms ahead of the line. Models have focused in on a potential severe weather window of 3:00-9:00am Saturday morning.

The high-resolution NAM3 model forecast radar valid from midnight tonight through 6pm Saturday gives us an idea of what to expect as the line crosses Memphis proper in the 5-9am window. (WeatherModels.com)

Flooding threat

Over the past couple weeks, we have received 1.5-3″ inches of rain across the area. This means our ground is pretty wet and a Flash Flood Watch has been issued due to the expectation of additional heavy rain. Ahead of the line, showers are possible, which will only aid in saturating the ground. However, this system may produce 2-3″ of rainfall by mid-morning Saturday. A significant concern with this event will be flooding. Low lying areas should be avoided or monitored closely to ensure your safety. It is especially important that you exercise extreme caution when driving at night in or after heavy rain. The condition of the roadways is difficult to gauge in the dark! Remember: Turn Around, Don’t Drown!

Straight-line wind threat

The wind energy associated with this system is very significant. With surface wind gusts over 30 mph and wind of 80-90 mph at just 5,000′ above us, the stage is set for a potential damaging event as wind with this system could reach hurricane strength in spots. That means we may be seeing surface wind on the magnitude of 70+ mph! A Severe Thunderstorm Warning with winds this high should be taken as seriously as a Tornado Warning! Take action and take cover in an interior room on the lowest floor, away from windows, if a Severe Thunderstorm Warning is issued. With saturated ground, it won’t take much for trees or possibly power poles to be knocked over, so make sure to charge all devices are charging overnight to ensure you can still receive weather updates and other information if the power goes out.

Tornado threat

The tornado threat with this event appears to be limited to a low potential for spin-ups, however these cannot be ruled out. Higher tornado threats exist to our southwest in southern AR, northern Louisiana, and western Mississippi. However, with storms moving at highway speeds due to the magnitude of the wind, even a spin-up tornado can move very quickly. Be ready to act if a warning is issued!

We also highly recommend you have multiple ways of receiving warning information. That includes commercial TV and radio, NOAA Weather Radio, Wireless Emergency Alerts on your cell phone, as well as a configurable mobile warning app like SW+ Alerts in the MemphisWeather.net app. SW+ Alerts is a low-cost, highly-customizable method of receiving warnings for specific locations you program in. It will even wake you up for the most severe warnings overnight! Learn more and download the app at App.MemphisWeather.net.

Despite all the excitement Saturday morning, Saturday afternoon looks much better! There may be trees down or power outages, but weather conditions themselves improve. A few straggling showers are possible and it will remain breezy, but clouds will begin to decrease into the evening hours with temperatures hanging out in the mid 50s during the afternoon before falling into the 30s overnight.