Between now and Wednesday there will be a few chances for showers and storms. And some of these may even be severe. A Marginal Risk for severe weather stands for parts of the area Monday and other parts of the area on Tuesday. That is a “1” on the 1-to-5 scale where “5” is the highest risk for the most significant severe weather.
But the concern for Monday and Tuesday is mainly for gusty wind and hail.
Wednesday, there is an Enhanced Risk for severe weather over the area. That is a “3” on the same 1-to-5 scale.
The main concerns on Wednesday are for heavy rain, gusty wind, larger hail (up to tennis ball sized) and the risk for a few tornadoes. And a strong tornado is possible, too.
From the SPC
The Storm Prediction Center has fine-tuned the forecast a bit from yesterday. It has shifted the Enhanced Risk a bit farther north. That said, it still covers most of south Mississippi
Here is the latest discussion:
…Synopsis…
A vigorous upper low moving across central portions of the U.S. will once again be the primary upper feature of interest, as it tracks from the Texas/Oklahoma Panhandle vicinity early, to southern Missouri through the end of the period. Ahead of this system, moderately strong/accompanying flow will spread across the lower Mississippi and Tennessee Valleys and central Gulf Coast states with time. At the surface, a low is forecast to cross Oklahoma during the day, and then should cross the Ozarks through the evening eventually reaching the western Illinois vicinity by 18/12Z. Widespread thunderstorms, and substantial / accompanying severe risk, can be expected in advance of this system.
…The AR/LA vicinity eastward to portions of TN/GA and the FL Panhandle…
Showers and thunderstorms are forecast to be ongoing from Kansas southward to Texas ahead of the advancing upper system and associated cold front, and eastward across the central Gulf Coast states in a zone along a west-to-east warm front. Some ongoing severe risk will likely exist at the start of the period. With time, as moisture streams northward from the Gulf of Mexico beneath steepening lapse rates, modest heating will push surface-based CAPE into the 1000 to 2000 J/kg range with a broad warm sector stretching from the AR/LA vicinity eastward to the southern Appalachians.
Convection is forecast to increase in response to the destabilization, as persistent UVV occurs not only in the vicinity of the cold and warm fronts, but also more broadly within the general warm-advection regime. Southerly low-level flow, veering and increasing to around 50 kt from the west/southwest at mid levels will provide shear favorable for supercells. Additionally, ample low-level shear is expected to evolve through the day — particularly near the aforementioned warm front which should drift northward across Arkansas and align west-northwest to east-southeast from far southern MO to central GA by early evening.
As such, tornado risk may be maximized near this boundary — across the AR area during the day, and then later increasing eastward across AL and perhaps into GA as well, as low-level flow increases into the evening/overnight. In addition to tornado potential — including the risk for a couple of significant tornadoes across a broad area represented by the ENH/30% risk area, large hail and damaging winds will also occur in some areas.
Risk will continue through the overnight hours, tapering from west to east across the lower Mississippi Valley but continuing across the central Gulf Coast states and into the southern Appalachians through 18/12z.
Courtesy: spc.noaa.gov
As noted above, the SPC is more concerned about tornado development near the warm front. This is something we discussed yesterday as a possibility.
Latest from the Analogs
The CIPS Analogs continue to offer a historical perspective on the situation. I’ve been using the CIPS Analogs for more than five years now and I’ve found that – a lot like other parts of history – they can be rather useful for helping predict the future, too.
Compared to yesterday, you can see that the Top 15 analogs now do have a few “dud” events mixed into the bunch.
There may be a handful of different reasons for this, but I won’t take the time to do a deep dive into that here. Instead, suffice it to say, it is good news. Nice to know that a setup for an event doesn’t always produce severe weather.
That said, underneath the Top 15 analogs, the individual threats for more significant severe weather do point to south Mississippi having the best bet – regionally speaking – for seeing severe weather.
So while, in this particular forecast from the SPC, their concern may lie farther north. Historically speaking, these types of events tend to favor severe weather reports in south Mississippi.
New Data
The 12z data is just starting to come down, but the mid-morning data from some of the shorter-range guidance as well as some of the global models was pointing to an interesting situation where the most potent environment for severe weather development may not be ‘in phase’ with the time when the best forcing occurs.
That is good news for south Mississippi. You can almost think of it like this: You have a neatly stacked, perfectly structured pile of wood for a bonfire with a bunch of gasoline poured all over it. But the guy with the matches won’t show up until after you dismantle the stack and only have a few logs leftover.
Could you still have a good bonfire after you dismantle the stack? Sure. There is still gasoline all over the wood that is left over. But it wouldn’t be as good as if the guy with the matches was around when everything was neatly stacked and ready to go.
Here is an example: Wednesday morning, as the sun is rising, often the atmosphere is at its most stable. But in this case for south Mississippi, this may be the most primo time for severe development.
On the left, that is what the estimated radar will look like on Wednesday morning. On the right is what the atmosphere will look like – mathematically.
And, mathematically, that is about as favorable an environment as you would want for severe weather and tornadic development in south Mississippi. But, according to the data, there won’t really be many storms around to take advantage of it. If any storms do develop, they may be severe. But the data shows a lack of convection at that time.
The guy with the matches doesn’t show up until later in the day, when the atmosphere isn’t a neatly stacked pile of wood. And the atmosphere, a lot like the leftover logs in our example above, will still have ample ‘juice’ to make severe weather. It just won’t be as ‘juiced’ as in the morning.
That said, in the afternoon, there is still a primed atmosphere as storms develop. So, not “great” news, but some “good” news.
Timeline & Threats
Right now, it looks like the timeline of events will be two potential rounds of storms.
Round One
The first round would be in the morning between 6am and 10am. If storms develop – and that is a reasonably if – they would have the chance to be supercellular and severe. The main concern in the morning would likely be heavy rain, gusty wind and large hail.
The tornado threat may be limited by a lingering inversion, but the threat for tornadoes would be dictated storm-to-storm and not something on the wide scale that could be determined as higher or lower. And the threat for tornado development would increase later in the morning.
Round Two
The afternoon / evening event will be Round Two. This will be between 11am and 8pm. This is when individual storms ahead of the front will develop and move across the area from southwest to northeast. These storms will have the ability to get rooted, organized and develop supercellular characteristics. These storms have the potential to turn severe as well.
The main threats in the afternoon will be heavy rain, frequent lightning, wind gusts up to 60mph, hailstones up to the size of tennis balls, and tornadoes. A strong tornado (EF2 or EF3) can’t be ruled out, either.
Round Three
The third round will be as the cold front passes through between 9pm and 4am. These storms may not be as potent, depending on how much the atmosphere is worked over by rounds One and Two. But it may have some stronger storms with heavy rain, frequent lightning and some gusty wind at times.
The Bottom Line
Showers storms and the potential for severe weather will persist during the next few days – Monday, Tuesday and Wednesday. But the main threat for the most significant severe weather will be on Wednesday.
The timeline of events on Wednesday leave the area with an “all day” event where the potential for storms exists for longer than 12 hours and may start before some people wake up and linger around until after some people go to bed.
This doesn’t mean it will be storming all day long. There may be times during the day on Wednesday where it is actually “nice” outside. But, there may also be times when it is raining sideways, lightning is flashing and hail is pummeling your rooftop. Determining when your specific house or workplace will see rain, storms and severe weather is still a bit out of reach.
For now, just make sure you have your NOAA Weather radio setup with fresh batteries. Make sure it is set to the right channel and, if capable, that it is set to alert you when a warning is issued for your county. Also, download a weather app to your phone that will ping you when a warning is issued for your area. Having multiple ways to receive a warning is like setting two alarms to make sure you actually get up in the morning! Redundancy is key!
