Severe WX Severe Threat 25 March 2021

[gangstonc]

HRRR and 3K nam are printing very high ceiling events. What is the mitigating factors in this event to watch for? Last week the CAD won out, for north AL.

Convection getting in the way of the warm front and stabilizing things
Junk convection in the warm sector is almost always a concern.

 

[Kory]

The euro is showing a lot of convection in the warm sector on the 06z run. I’ve noticed it tends to “over-convect” down along the coast a lot with these set ups. But, there is notable upper jet diffluence over the warm sector (particularly North AL, North MS) which may mean more convection with the cleaner warm sector placed south.

 

[MattPetrulli]

Even with junk convection with the big dynamics and thermodynamics at play here, still probably gonna get at least a few strong tors somewhere.

 

[Richardjacks]

I am not convinced the warm sector will clean out...for one, in most recent runs, the amount of time is limited for that to happen. I could be wrong, we will see.

 

[Kory]

Even with junk convection with the big dynamics and thermodynamics at play here, still probably gonna get at least a few strong tors somewhere.

It’s more of where the northern cut off is. Even last April with the Easter event, that was a junky warm sector that still managed to produce long tracking strong/violent tornadoes.

 

[pohnpei]

It’s more of where the northern cut off is. Even last April with the Easter event, that was a junky warm sector that still managed to produce long tracking strong/violent tornadoes.

Yes, it don't need the whole warm sector cleaned out to have a violent tornado. The things that can happen on a whole cleaned out 3000CAPE/60KT LLJ warm sector will be just unimagiable.

 

[Richardjacks]

Yes, it don't need the whole warm sector cleaned out to have a violent tornado. The things that can happen on a whole cleaned out 3000CAPE/60KT LLJ warm sector will be just unimagiable.

True, but they tend to be more long tracked with an open warm sector for obvious reasons

 

[TornadoFan]

:/

 

[kcyalater]

I think there is a pretty decent chance the modeled convection is a wet blanket here. The amount of moisture is significant

 

[Liberty4dayz]

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

So, if I'm reading that right. Seeing as I live outside Chattanooga in the valley...I shouldn't worry so much about living in a newer model manufactured home? The worst action will stay west and south?

 

[Kory]

So, if I'm reading that right. Seeing as I live outside Chattanooga in the valley...I shouldn't worry so much about living in a newer model manufactured home? The worst action will stay west and south?

I would be weather aware tomorrow. These storms do not know outlook boundaries.

 

[Kory]

I think there is a pretty decent chance the modeled convection is a wet blanket here. The amount of moisture is significant

There is also a stronger EML that may prevent the junkier convection that was seen last Wednesday. And unlike the last trough which was moving due east overtop, this one is glancing by NW with smaller height falls. It is digging quite far south so it is tapping the subtropical jet...higher PWATS.

 

[NorthGaWeather]

Even though I don't like to champion individual runs of a model, the 12z HRRR does a decent job of cleaning out the warm sector across much of MS/AL with capping (more pronounced in MS/West AL) through the late morning/early afternoon. After 18z, all hell breaks loose.

 

[pohnpei]

12Z HRRR still shows mutiple supercell develop ... It is quite ugly looking thing I have to say.

 

[NorthGaWeather]

So, if I'm reading that right. Seeing as I live outside Chattanooga in the valley...I shouldn't worry so much about living in a newer model manufactured home? The worst action will stay west and south?

Even though higher probabilities are to your south and west, there is still potential for significant severe weather to affect your area. Just have a plan of action in place in case you're placed under a watch/warning tomorrow.

12Z HRRR still shows mutiple supercell develop .
View attachment 7396

That's a spicy meatball.

 

[The Nino]

12Z HRRR still shows mutiple supercell develop ... It is quite ugly looking thing I have to say.
View attachment 7396

 

[CheeselandSkies]

12Z HRRR still shows mutiple supercell develop ... It is quite ugly looking thing I have to say.
View attachment 7396

For what it's worth, seems like it has been much more consistent with long-tracking, high-end (reds and purples) UH streaks than it was prior to last Wednesday. Of course the number and exact placement has varied from run to run but that's the general theme.

 

[pohnpei]

For what it's worth, seems like it has been much more consistent with long-tracking, high-end (reds and purples) UH streaks than it was prior to last Wednesday. Of course the number and exact placement has varied from run to run but that's the general theme.

Yes, last wednesday never shows many UH streaks until last 12 hours or so. The storm mode never being depicted like this if I remember it correctly. Certainly many things can change in next 36 hours, but it is definitely concerning at this point.

 

[Bama Ravens]

So, if I'm reading that right. Seeing as I live outside Chattanooga in the valley...I shouldn't worry so much about living in a newer model manufactured home? The worst action will stay west and south?

What I posted is specific to the area covered by the National Weather Service in Birmingham. Plus, this is an outdated forecast discussion now.

 

[Richardjacks]

The 12z nam trends a little closer to euro and gfs with stronger low and little further south. Also, shows very little time between morning rain/leftover clouds and afternoon storms firing. Volatile environment, just not sure I completely believe it as morning rain is slow to leave with little clearing, in any.