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Severe WX Wednesday/Thursday/Friday April 17th-19th Severe Threat

bwalk

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At 9pm the second line of storms in Mississippi has intensified somewhat and taken on it’s own identity (so to speak). WSFA is saying this line will reach central Alabama at about the same time as increasing instability values (midnightish).
Help me understand. The atmosphere would seem to be very worked over after this first line with no time to recover. What am I missing?
 

JayF

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At 9pm the second line of storms in Mississippi has intensified somewhat and taken on it’s own identity (so to speak). WSFA is saying this line will reach central Alabama at about the same time as increasing instability values (midnightish).
Help me understand. The atmosphere would seem to be very worked over after this first line with no time to recover. What am I missing?
Let me jump over and take a look. I have been following the North Alabama Storms.
 

jmills

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The low has pushed into Tennessee. I believe Alabama is in the clear.

The HRRR continues to try and do something overnight in SE Alabama. Pressure falls would likely keep surface winds backed, but the main limiting factor is instability. IF there is enough instability ahead of that final line then I could see something happening.
 

JayF

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There is a line of storms coming into Sumter and Choctaw counties that could become Severe Thunderstorms. Some rotation in those storms. It just depends on the Atmosphere what they end up doing.
 

bwalk

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At 9:30 a semi discreet cell has formed ahead of the main second line of storms. Not sure it qualifies as true discreet cell due to all the wacky atmosphere dynamics (caused by the passing of the first line earlier) but it has a high dbz core in the middle of it. Cell located nw of Camden, Al.
 

Taylor Campbell

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The line of storms crossing the MS/AL border, and new storm development along, and ahead of it is what has been modeled to bring the greatest threat for my area, and for central/southern Alabama.
 
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WesL

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NWS BMX reporting a fatality in Wattsville in St. Clair County, AL. Tree fell on a home near US HWY 231 killing one person.

Source: Local Storm Report - BMX
 

Equus

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Honestly looks like a bona fide derecho given density of reports. I'm not sure if I've seen a more solid blue swath on unfiltered storm reports than there is over central MS.
 

Taylor Campbell

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Best severe/tornadic parameters are surging inland. Helicity streak spikes with new storm development mainly east of I-65, and south of I-20, and along the I-85 corridor between 12-4am.
 

jmills

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VWP derived hodographs from KEOX and KMXX show more than ample helicity and deep layer shear for tornadoes. It will be interesting to see how the storms currently straddling the AL/FL panhandle border behave as they move northeast into a kinematically favorable environment.
 
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Possible watch soon

mcd0395.gif

Concerning...Severe potential...Watch possible

Valid 190444Z - 190645Z

Probability of Watch Issuance...40 percent

SUMMARY...Trends are being monitored for a possible increase in
thunderstorm organization and intensity during the next couple of
hours over the central Gulf coastal region. A ww issuance is
possible, but remains uncertain and will ultimately depend on
convective trends.

DISCUSSION...Storms have recently shown an increase in coverage over
the central Gulf coast region including extreme southern AL and the
far western FL Panhandle. The convection is discrete, but has so far
shown very little tendency for organization. Activity appears to be
forming in association with an increase in the southern extension of
the low-level jet which is responding to the next in a series of
vorticity maxima rotating through the base of the synoptic trough.
Dewpoints have increased to around 70 F south of the warm front,
which has contributed to destabilization (MLCAPE from 1000-1500
J/kg) along the central Gulf Coast region. However, the atmosphere
still has not yet fully recovered from the effects of previous
convection. Nevertheless, given increasing forcing for ascent,
modest instability, sizeable low-level hodographs and strong
effective shear, this area bears watching next couple hours for
evidence of organization and possible supercell development.
 

Taylor Campbell

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By “inland” do you mean out of the Gulf?

Yes, the moisture is coming out of the Gulf. It is already very rich across extreme south Alabama. Stations there are reporting 70 degree dewpoints with temperatures still in the low-mid 70s!

DFF32FC0-34AA-40BA-B760-87D1CA603D4E.png
 

jmills

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Jmills this is what you were just saying.
Yep. The storms I mentioned have maintained ~45kft echo tops per KMOB for a little while now, which makes sense given the rich, warm boundary layer they have to work with. However, they have failed to maintain any sort of low level circulation or strong mid level mesocyclone, which I expect to change pretty soon as they move into a more sheared environment. Time will tell though.
 

Taylor Campbell

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Round 2 here we go. The storms appear to be getting stronger. There’s now a severe thunderstorm warning out for one of them.
 
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