Severe WX Severe Threat 25 March 2021

[Richardjacks]

Surprised the soundings are not showing more upside down "v"'s near the surface...typically goes along with the cap.

NEVERMIND....

 

[David in SW Blount]

I'm worried that there will be a lot of public complacency with this event after last week didn't deliver as much as people in many areas expected.

 

[HazardousWx]

I'm worried that there will be a lot of public complacency with this event after last week didn't deliver as much as people in many areas expected.

Yes, because that one had a LOT of people's attention.

 

[BraxBanksOKWX]

So, the 18z NAM 3k was downright nasty.

 

[Fred Gossage]

And to put the NAM/3km NAM into perspective, compared the all the other models, it is slightly less organized with the trough and low pressure. Despite what the NAM package shows (a higher-end threat), it is on the less bullish side of the possible solutions.

 

[Richardjacks]

And to put the NAM/3km NAM into perspective, compared the all the other models, it is slightly less organized with the trough and low pressure. Despite what the NAM package shows (a higher-end threat), it is on the less bullish side of the possible solutions.

Correct, quite the discrepancy between nam and euro for example.

 

[Fred Gossage]

Correct, quite the discrepancy between nam and euro for example.

HRRR is kinematically in the Euro/etc camp. Even the latest GFS now has a 990mb low over south IL Thursday evening that deepens into the 980s as it moves into IN. I am getting the idea more and more that this is one of those cases where the NAM is doing its classic thing of stringing out shortwave energy. The fact that it still promotes what it does is pretty eye opening. Still, I'm waiting to see the 00z models tonight before we change our L-bar and graphics backgrounds to red at the station.

 

[CheeselandSkies]

Someone said on another forum that this will be another positively tilted, closed low scenario (like last Wednesday, and thus prone to many of the same potential limiting factors/failure modes). However, looking at the 500mb chart from today's 12Z GFS, I see a big open trough with a slightly negatively tilted shortwave rolling through it (look at the 549 to 558 dam lines from NC KS to NE TX). Either I'm missing something or they are.

 

[Fred Gossage]

Someone said on another forum that this will be another positively tilted, closed low scenario (like last Wednesday, and thus prone to many of the same potential limiting factors/failure modes). However, looking at the 500mb chart from today's 12Z GFS, I see a big open trough with a slightly negatively tilted shortwave rolling through it (look at the 549 to 558 dam lines from NC KS to NE TX). Either I'm missing something or they are.

You are... You're missing having your head up your donkey like where they have theirs firmly placed.

 

[Bama Ravens]

BMX hinting at a significant event (last sentence) with their latest afd:

They’ve added this for Wednesday night through Thursday:


.LONG TERM...
/Updated at 0250 PM CDT Tue Mar 23 2021/

Wednesday night and Thursday.

Models are in good agreement with showers and thunderstorms
increasing from south to north Wednesday night as an upper warm
front lifts northward. Localized heavy rainfall possible across
areas north of I-20 Wednesday night. Expect most of the rain
associated with the warm front will be north of central Alabama by
sunrise Thursday. A relative lull in showers and thunderstorms
Thursday morning will allow for surface temperatures to warm and
instability to increase. With surface dewpoints in the middle to
upper 60s, surface based CAPE will likely rise to 1500-2000 J/kg
Thursday afternoon, especially across the western counties. High
0-6km bulk shear and strong low level veering will be favorable
for tornadoes. Highest threat area will reside along and west of
the I-20/59 corridor. Models weaken forcing and low level shear
quickly Thursday evening and expect severe threat to be greatly
diminished by 10 pm. For this reason, will lower severe threat for
areas east of I-65.

58/rose

 

[CheeselandSkies]

You are... You're missing having your head up your donkey like where they have theirs firmly placed.

Thanks, Fred but what about the meteorology behind it? Am I accurate in discerning the shortwave axis there?

 

[Fred Gossage]

Thanks, Fred but what about the meteorology behind it? Am I accurate in discerning the shortwave axis there?

It's a low amplitude, negative tilt, fully open shortwave trough. I don't see how anybody could possibly say any differently. Even the NAM solution that's a touch more strung out than the others is an open shortwave, not a closed upper low.

 

[Clancy]

Models sure are showing some wild things for Thursday. Hope everyone can get the word of this event (without blowing it off because of perceptions of last week) and have time to prepare.

 

[Marshal79344]

I cannot be the only person who is noticing how the models are uptrending on the intensity of the surface low, which was literally nonexistent on some of those CAM's yesterday. This is going to be another major issue due to a more organized surface low favoring more OWS development.

 

[CheeselandSkies]

18Z GFS holds serve with the same general 500mb look as 12Z. Additionally, there appears to be a splitting jet at 300mb. If I understand it correctly, this serves to enhance upper-level divergence/vertical motion?

 

[Keldeo]

STPs are crazy on the HRRR

 

[andyhb]

A reminder that the wxbell calculation of STP is off due to improper input parameters, it is usually far higher than outputs on any other site.

 

[MNTornadoGuy]

Pivotal Weather has a max STP value of ~7 on that same run of HRRR

 

[warneagle]

Southern MS/AL could also have some major flooding issues by the end of this, there are some pretty massive rainfall totals down there.

 

[KevinH]

To me, Northern/Central Alabama and Mississippi always seem to get the worst of storms. Not just for the past week, but overall. I live in Columbus, Georgia and we do NOT get the kind of storms and threats these parts of Dixie Alley do (yes, I am going to still call Dixie Alley, DIXIE ALLEY. Screw The Weather Channel and Byron Allen).

On Twitter, I suggested that N AL and MS *SPECIFICALLY* have a nickname of their own to distinguish them from the rest of Dixie: #AlabamaAlley

I mean, I am JUST saying *shrug*