Recap of Mid-South severe weather on Friday, 3/2/12

For the second time in 3 days, the city of Memphis and immediate suburbs were largely spared from possible severe weather. As forecast, the vast majority of the severe weather, including multiple tornadoes and 27 reported fatalities as of this writing, occurred east of the metro, although storms along the cold front fired over Fayette and Marshall Counties. Large hail was reported in Grand Junction, Fayette County, from that storm.  Below are the preliminary storm reports received by NWS-Memphis today.

NWS-Memphis preliminary storm reports. Red = tornadoes; purple = hail; yellow = wind. 

Heading into today, a widespread and potentially devastating setup prompted the issuance of a rare high risk outlook for central KY and TN and a very large moderate risk surrounding the high risk. The 8:00am outlook from the Storm Prediction Center (shown below) depicts the area of concern.

8:00am severe weather outlook from SPC.

The result (as of 6:30pm CST) is shown below in terms of the number of severe weather warnings issued.  The warnings were, as expected, largely within the moderate and high risk zones shown above, indicating that the SPC forecasters had a good handle on the area most likely to be affected.

NWS-issued warnings through 6:30pm. Tornado = red; T'storm = blue; Flood = green.

With the passage of the cold front through the Mid-South at mid-afternoon, a drier and stable airmass was ushered in.  High pressure will continue to build in bringing cooler, though not unseasonably cool, weather for the next few days.  Certainly much cooler than the record high of 83 degrees that was set at Memphis today!

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Latest look at Friday’s severe weather threat

After a nearly perfect afternoon across the area today, it’s hard to want to look ahead to the next system that brings the risk of thunderstorms and severe weather, but with its arrival less than 24 hours away, that’s what we must do! We first detailed the severe weather threat with this system in a blog post last night, and looking again today it appears a bit clearer, and for us in the metro, that may mean good news.

As mentioned last night, there are two distinct periods of interest. The first arrives late tonight, primarily after midnight to near dawn, as a warm front to our south begins to surge northward through the area. With its passing, showers and a few thunderstorms may break out near it. Unfortunately, models are still not in great agreement on just how much coverage of rain and thunder may occur, so confidence is not particularly high for this portion. Should development take place in the metro area, the increasing instability associated with the warm front’s passage could promote the development of a few stronger “elevated” thunderstorms with the possibility of hail. Better chances for this activity will likely exist to our northwest, over northeast Arkansas and southeast Missouri. However, don't be surprised if thunder wakes you up early tomorrow morning!

Possibility of early Friday AM rain or storms shown in the GFS model

Once the warm front has cleared the area, the atmosphere over the Mid-South will become “capped” to additional thunderstorms Friday morning, similar to what occurred Wednesday. Some sun may break out and temperatures will become quite warm, rising into the 70s with gusty southwest winds. All of these factors will lead to building instability values, as the primary storm system and associated cold front approach from the west. Sometime during the afternoon, the “cap” will break and numerous thunderstorms will develop in advance of the front, with some quite likely to be severe.

However, the big question that remains for those of us here in the metro is just how soon thunderstorms develop. Models are in better agreement for this round of weather, and fortunately for us they are leaning heavily toward the idea that development will primarily occur east of the city of Memphis, and perhaps entirely east of the metro area. In a conference call with NWS partners this afternoon, including MWN, NWS-Memphis agreed with this idea (see graphic below), and so do we.

Graphic from NWS-Memphis depicting Friday's severe weather threat

That said, there still remains some risk that thunderstorms develop early and far enough west to impact this area, especially those just east of Memphis itself. One possible scenario is that thunderstorms begin their development right over the metro, but don’t begin to mature and become severe until they move just east. It’s likely to be a close call, so we encourage everyone in the metro to remain weather-aware with this one. The atmospheric parameters in place for this event favor all modes of severe weather, including a threat for tornadoes.

In fact, those parameters will almost certainly come together north and east of us, where the Storm Prediction Center has already highlighted a “Moderate Risk” for severe weather (see graphic).  It will be these areas likely to be in the thick of a significant severe thunderstorm and tornado outbreak tomorrow. If you have interests in these areas, please make sure they are keeping up with the weather.

Storm Prediction Center severe weather outlook outlook for Friday 

Back here in the metro, once the cold front clears, much cooler temperatures will be filtering into the area. Readings nearing 40 are likely by the time you wake up Saturday, and that will lead into a fantastic weekend overall, though certainly cooler than the past several days! A much calmer pattern is also looking to continue for much of next week as well.

Continue to stay with MWN through the night and into Friday for the very latest on this system. If necessary, we’ll be providing nowcasting of any thunderstorms moving through the metro area via social media. Also, don’t forget our StormWatch+ service that will immediately notify you on your smartphone to any severe weather alerts issued, even if you are asleep! For more, visit StormWatchPlus.com.

--Kevin Terry, MemphisWeather.Net

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For weather information for Memphis and the Mid-South, where and when you need it, visit MemphisWeather.net on the web, m.memphisweather.net on your mobile phone, download our iPhone or Android apps, or visit us on Facebook or Twitter.