Severe WX Severe Weather Threat - December 8th-10th, 2023

[JBishopwx]

MEG AFD:

NBM and multiple other deterministic models depict higher surface
temperature and dewpoints on Saturday. This has a direct
relationship to the likelihood of surface-based convection. The GFS
is more aggressive in CAPE with a 30% chance of CAPE >1000 J/kg, but
a 70% chance of CAPE> 500 J/kg. The ECMWF has a 0% probability of
CAPE> 1000 J/kg, but has a 50% chance of CAPE> 500 J/kg on Saturday
at 18z.

While CAPE seems relatively low, the shear remains to be elevated
with 0-1 km shear nearing 30 kts and 0-6 km bulk shear nearing 60
kts. While the storm mode appears to be linear (QLCS) with strong
forcing. Given the parameters, damaging winds and embedded tornadoes
(brief spin ups) look to be the primary threats. Large hail and
heavy rain are also possible.

This is largely dependent on how much instability is present and
how much moisture can advect back into the region. Models are
hinting at pre-frontal showers to arrive as early as Friday
evening, which will increase cloud cover and limit surface based
convection. In addition, near-surface based parcels may have
access to strongly veered vertical wind profiles in the surface to
850mb layer which can limit intensity of any thunderstorm
updrafts. These factors contribute to lower than average
confidence level in severe thunderstorm chances Saturday afternoon
and evening.

 

[JBishopwx]

 

[Taylor Campbell]

The GFS still has it going down for MS into Alabama. I hope BMX is speeding up that radar maintenance.

 

[KevinH]

The GFS still has it going down for MS into Alabama. I hope BMX is speeding up that radar maintenance.

I still don’t understand why maintenance is scheduled during these times.

Even if they are scheduled far in advanced, don’t schedule them for an area during their peak season(s).

That’s like scheduling KTLX radar (OKC) for May

 

[JPWX]

Me thinks this could be a bigger deal. A south wind near 20mph along with a temperature contrast between Saturday/Sunday from 70 down to 49. (21 degree difference). While that doesn't sound like a big temp difference, upper 60s/low 70s in December is always a bad sign.

 

[KevinH]

Me thinks this could be a bigger deal. A south wind near 20mph along with a temperature contrast between Saturday/Sunday from 70 down to 49. (21 degree difference). While that doesn't sound like a big temp difference, upper 60s/low 70s in December is always a bad sign.

Bigger deal for the “Oklahoma of the Deep South” (MS &AL)?

I would not be surprised if the threat is increased and/or shifted. We all know how unpredictable Dixie is.

 

[JPWX]

Yes @KevinH. Not to mention the fact that models might be underdoing the CAPE and max temperature/dewpoints.

 

[KevinH]

Yes @KevinH. Not to mention the fact that models might be underdoing the CAPE and max temperature/dewpoints.

Oh that’s right. A few people have mentioned the models under doing stuff in the winter months.

sigh

 

[MichelleH]

Me thinks this could be a bigger deal. A south wind near 20mph along with a temperature contrast between Saturday/Sunday from 70 down to 49. (21 degree difference). While that doesn't sound like a big temp difference, upper 60s/low 70s in December is always a bad sign.

Yep.

 

[treypops]

Yes @KevinH. Not to mention the fact that models might be underdoing the CAPE and max temperature/dewpoints.

Maybe. I'm not sold on this yet.

 

[KevinH]

Maybe. I'm not sold on this yet.

I am not sold either way as well. Still a bit too early personally. I’ll start paying attention late tomorrow and Friday lol

 

[TH2002]

Maybe. I'm not sold on this yet.

Not 100% sure if I'm sold on this myself, but Saturday is going to be my busiest work day this week so I'm not gonna be able to devote nearly as much attention to this either way... on the bright side, I was able to get TW and my favorite free radar app working on my work phone (a flip phone) so I can at least chime in when things slow down a bit.

 

[ashtonlemleywx]

18z NAM sh*t the bed. Not looking very impressive at the moment. If things don't change on next few runs I see this being a D1 slight.
I'm thinking morning showers/cloud cover is going to limit instability.

 

[JPWX]

GFDL

 

[Clancy]

GFDL

Very healthy squall line, though iirc SHiELD really overdoes UH typically speaking.

 

[UncleJuJu98]

Very healthy squall line, though iirc SHiELD really overdoes UH typically speaking.

I smell spin ups lol

 

[tennessee storm chaser]

Within 48 hours we went from a pretty good tornado setup to a mainly squall line system …. I pass

 

[JBishopwx]

One model runs, and everyone is giving up on this system... I like to see several runs of the NAM3k and HRRR runs before I write it off. Quick spin-up tornadoes from a squall line are just as dangerous. There's no need to blow it off this early in the ball game.

 

[Tanner]

Within 48 hours we went from a pretty good tornado setup to a mainly squall line system …. I pass

Seems to be a trend this year with models...very compelling looks from days out with consistency among ensembles and then we get within a few days and it falls apart. But let the weather gods speak for themselves! I'm still hoping for some winter weather up here in the northeast.

 

[JPWX]

And let's just remember that the EF-0 tornado (pictured below that I just happened to capture on my GoPro 11) that occurred 2 miles west of Smithville, MS on February 16th happened on a Level 3 Enhanced Risk with a 10% SIG TOR hatch. Day 3 was just a Slight Risk.

March 24th: Day 3 Enhanced Risk became a Moderate Risk by Day 1. EF-3 Amory, MS happened.

Don't write it off yet. I've made the mistake before writing off an event that ended up producing more than anticipated. Never again.

I honestly don't care what the models show or don't show at this point. Models are a tool to help, but knowing how it works across the Gulf States and learning from past events is the way to do it. A threat is a threat no matter the risk. Heck the southern Itawamba County tornado in June occurred during a 2% TOR prob and then the Muldon, MS tornado in southern Monroe County that occurred on January 12th also occurred in a 2% TOR prob.