I know, I know. I’m full of good news. The last thing this area needs is more rain. And severe weather. But Mother Nature continues to sling it this direction.
As the next system slides through, it looks like surface low may slide by a bit closer to the coast. That would open the door for more rainfall for the area. That said, it would also limit the overall threat for significant severe weather. While heavy rain, lightning, gusty wind, hail and the potential for a tornado would still exist… The potential for strong tornadoes and wind gusts exceeding 70mph would be limited.
Currently the Storm Prediction Center is still showing a Slight Risk for severe weather for the same areas shown yesterday with only a slight change to the outlook risk area.
The main change was to limit the threat area to closer to the coast.
The breakdown
The next system is going to slide through the region and open the door for storms to pop off starting Tuesday afternoon. That threat for storms in the region will continue through the overnight hours Tuesday and into Wednesday morning.
The 12z GFS Karrie Meter maps (running a bit cooler than spreadsheet numbers) show highest risk confined closer to the Gulf overnight Tue-into-Wed.
00z GFS just got done rendering. Numbers there show similar trend. pic.twitter.com/Fofxq7ynMM
— Nick Lilja (@NickLilja) March 1, 2020
From the SPC:
Medium-range guidance is in good agreement that a modestly moist and unstable air mass will be in place from south TX northeastward across the Lower MS Valley and Southeast on D4/Tuesday. This air mass will exist ahead of deep upper low likely centered over northwest Mexico early D4/Tuesday. Guidance continues to struggle with consistency regarding the evolution of this upper low, with the GFS remaining the most progressive. Even with the timing differences, it appears probable that thunderstorms will develop ahead of this upper low along a cold front from the TX Hill Country through the Lower MS Valley. General expectation is for a line of storms to move from central TX eastward along the and south of the front through the lower MS Valley. Confidence in the timing of this thunderstorm development is low but consensus in the location of highest coverage and most probable severe area is high enough to maintain and expand the 15% delineation already in place.
The CIPS Analogs from this morning are still pretty intent on the risk centering around Vicksburg, MS.
That said, now that the evening and overnight data is trickling in, it looks like that may shift further south and closer to th coast. And it may be a bit more limited than shown above.
The other concern is that the area that may see the heaviest rain may also shift south with it. The above map shows areas that received more than four-inches of rain from the Top 15 analogs. In other words, looking back in history at similar atmospheric setups, the top 15 times it looked most like this… the areas int eh map picked up four-inches of rain XX-percent of the time.
If the threat for flooding shifts south, there may be a stretch of very heavy rain across parts of south Mississippi given, historically, this is the type of setup that produces heavy rainfall events.
There is more evidence of that, too. The overnight model data is coming in tonight showing a plume of very – like, very very – moist air moving into the region.
This next system may feature record-setting atmospheric moisture for the region.
Based on SPC sounding climo data, the record for Precipitable Water at LIX for this date is 1.77.
00z GFS shows 1.75 – 1.95 around LIX. pic.twitter.com/vNxKWNsurh
— Nick Lilja (@NickLilja) March 1, 2020
If this were to verify, it would mean copious amounts of rain for the area. As one forecaster noted, the ‘two-to-four inches of rain’ window may be too small.
The Bottom Line
Storms and the potential for severe weather is still the name of the game, unfortunately. It is still a possibility for Tuesday and into Wednesday for South Mississippi. But it looks like flooding may end up being an important thing to watch, too.
The threats with any storm in the area will be heavy rain, frequent lightning, wind gusts up to 65mph, hail up to the size of quarters, and the potential for a brief and weak (EF-0 and EF-1) tornadoes. This is not looking like a severe weather outbreak, nor is it looking like a tornado outbreak. This is more along the lines of a regular South Mississippi severe weather threat
On top of that, there is new evidence to suggest that flooding may also end up being a concern. Currently, it looks like two-to-four inches of rain will be possible between Monday afternoon and Thursday morning – with a bulk of that falling on Tuesday and Wednesday.
The Timeline
Showers and storms may begin as earlier as Monday afternoon. These would be non-severe.
Storms and the potential for severe weather may arrive as early as Tuesday afternoon. As a warm front lifts through the area. That threat will linger through the evening, and into the overnight hours into Wednesday morning.
Thunderstorms will transition to being surface-based (meaning capable of producing tornadoes and very strong wind) to elevated (mainly rain, lightning, and hail) during the day on Wednesday. When that happens is still up in the air, so to speak. But at some point, it looks like we will transition out of a severe weather threat and into more of a flooding threat.
The threat for heavy rain will continue through the overnight hours on Wednesday and into Thursday morning.
