It looks like there may be a few rounds of showers and storms Tuesday, Wednesday and Thursday for south Mississippi. And there is the potential for severe weather each day, too. On top of that, there will also be the potential for flash flooding and river flooding during this time frame.
From the SPC (Tuesday)
As of this writing, the Storm Prediction Center has highlighted parts of south Mississippi and Louisiana with a Marginal Risk for severe storms. That is a “1” on the 1-to-5 scale where “5” is the highest risk for the most significant severe weather.
Numerous showers and storms should be ongoing along and ahead of the cold front from LA into MS, with an instability axis near the Sabine river at 12Z Tuesday. Much of this activity may be effectively elevated at this time.
By midday, surface parcels are likely to become better incorporated into the ongoing convection, with new development possible over central LA into southwestern MS. Although the upper trough will continue shifting away from the area, low-level convergence and ample moisture will ensure continued storm development, and a few severe storms will be possible.
Strong deep-layer shear as well as stronger low-level SRH with eastward extend may support a supercell or two. If the supercells can maintain access to the more unstable air to the southwest of the diffuse warm front, a tornado would be possible. Otherwise, locally strong gusts or hail is expected with mixed-mode storms.
Courtesy: spc.noaa.gov
It wouldn’t surprise me if the SPC increases sections of Louisiana and Mississippi with a Slight Risk (2 out of 5) during the overnight update for Tuesday.
From the WPC (Tuesday)
The WPC has issued a Marginal / Slight Risk for flash flooding across parts of southern Mississippi and Louisiana for Tuesday.
…20Z Update…
A deepening storm system across the Central U.S. will advance thunderstorm activity through the Lower MS Valley region through Tuesday afternoon. A residual surface boundary will become draped across the region, especially southeastern LA into southern MS/AL. The position of this front will be the focus for heavier showers/thunderstorms through the overnight hours as mid-level impulses, upper level divergence and instability increase and align under strong moisture flux.
Based on the latest 12Z model guidance, only minor adjustments made to the Marginal and Slight Risk areas.
…Previous Discussion…
The latest model guidance has a better consensus on where the heavier QPF will occur, but there is still some spread on where the Mesoscale features will be. The exact amounts and location of heavy rain focused along a residual surface boundary will have fairly big implications on the potential for flash flooding.
Most solutions show 1 to 4+ inches across the Mississippi Delta and surrounding areas, while a couple show localized maximums closing in around 6 inches. Hi-res guidance maintains embedded cells with rain rates around 1/1.25 inches through most of this period from far eastern Texas, across Louisiana and into Mississippi. In coordination with the local forecast offices a Slight Risk area was raised for southeast Louisiana and southern Mississippi. Training of storms may quickly reach or exceed local FFG.
Courtesy: wpc.noaa.gov
CIPS Analogs (Thursday)
By Thursday, it looks like the highest risk for severe weather may shift north of I-20 – in general. That said, the potential for severe weather remains south of I-20, it just may not be as widespread.
The CIPS Analogs shows that – historically – this type of setup tends to promote the development of more widespread severe weather north of I-20 and into Alabama.
But it also shows that, while not as widespread, there is still evidence to support that similar setups have produced severe weather south of I-20, too. With up to eight of the Top 15 analogs showing a long-track tornado along of south of I-20 in similar events
The interesting part of this is the analog table itself shows that the April 27th, 2011 Outbreak is one of the analogs. And that may sound scary. But lets look into that…
There wasn’t a “Total” tallied today from the CIPS data, but April 27th is the No. 4 analog for both 84 hours and 96 hours out. Yesterday is was higher. It was No. 1 the day before, too.
That is a good trend. And it misses the mark on 300mb heights and surface dewpoint. Pretty badly. Ranking in the Bottom 3 for both.
So while it is an analog, it isn’t a perfect analog. And it isn’t as high on the last as some other candidates.
Bottom Line (Tue/Wed/Thur)
Tuesday will feature showers, storms and the potential for severe weather as a line of storms pushes across south Mississippi. Severe storms may begin as early as 10am for some and stick around as late as 6pm for others. The main concerns are for heavy rain, frequent lightning, wind gusts up to 65mph and the possibility for a brief tornado.
Once the severe weather threat has subsided, the regular rain and thunder will stick around for a few extra hours. In some places it may rain for more than six hours on Tuesday.
Wednesday, the rain and potential for flooding will continue.
By Thursday another system with another line of storms will push through the area. Depending on how storms initiate, there could be supercells ahead of the line of storms that develops. Depending on storm mode, the main concerns will be heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of quarters, and the potential for tornadoes.
