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Severe WX Severe threat 3/30-3/31

OhOkayThen said:
Can't take much from hour 84 of the NAM, but here it is for the start of the event
View attachment 37351View attachment 37352
Click to expand...


That's...interesting. Quite a bit further north than recent runs of the GFS have been suggesting.

Sometimes when it first comes into range the NAM throws cold water on a setup that had looked big on the globals, and sometimes it does the exact opposite. Doesn't exactly help with the uncertainty. This is one of those frustrating setups where at Day 4 we don't really know anything more than we did three days ago. I've yet to see a solid trend one way or the other.
 
CheeselandSkies said:
That's...interesting. Quite a bit further north than recent runs of the GFS have been suggesting.

Sometimes when it first comes into range the NAM throws cold water on a setup that had looked big on the globals, and sometimes it does the exact opposite. Doesn't exactly help with the uncertainty. This is one of those frustrating setups where at Day 4 we don't really know anything more than we did three days ago. I've yet to see a solid trend one way or the other.
Click to expand...
I really don’t expect much resolution until we are within 48 hours. I do think we will end up with a substantial severe weather event. I don’t see this being a squal line either. The real question is the overnight Tornado threat. We won’t have that clarity until we get much closer to the event
 
I mentioned earlier how much the GFS has changed in terms of the intensity of this setup, specifically the tornado potential in the past 24 hours. For context, here's the GFS about 24 hours ago for 0-3km SRH:

1000000767.gif
Here's the latest 12z model scan for 0-3km SRH:

1000000764.gif
Of course more times than not it takes a minimum of 250 m2 s-2 in the 0-3km range to get a favorable setup of tornadoes, which you still somewhat see in the latest model run, but it definitely has dropped in the past 24 hours compare to the 06z run from yesterday.

As I am sitting here and typing this, I'm starting to disagree with the GFS in terms of how much it's underselling this setup, and that we'll start to get answers from the NAM runs as they start to come in here in the next day. After all, there's a reason you haven't seen the GFS model being brought up in the NWS AFD's.

But yeah, I don't buy it just being a squall line setup. We'll see what happens here when more data continues to be brought in.
 
Bulkshear said:
The threat is still significant. SPC doesn’t just hand out huge Day 5 outlooks. The model consistency is all over the place. You need to look at general pattern recognition rather than model by model at this point in time. What we really know is there will be plenty of instability pushing rather far north and sufficient wind shear that could lead to big issues. What we don’t know is the trajectory of the low/placement and other mitigating factors that really won’t come into focus until we have the CAM models. Even then if there is an appreciable tornado threat we won’t really know until the morning of the event.
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Replies like this make glad you started this thread lol
 
Here's latest WRF-ARW model run based on 06z GFS initial conditions, 9 km resolution, centered on Birmingham, AL.

Composite radar shows a "line" of discrete cells tracking across MS and AL.



test567.gif

The SBCAPE is interesting because it shows two major pushes of storm fuel -- the first into MS and western AL overnight, then a blow up across SE AL and central GA during the day on Monday.
test678.gif

A large portion of the area will have LCL's below 600m in the open warm sector, which favors tornado formation, conditional on other factors being present.
test789.gif


In the lowest part of the atmosphere (the lowest 500m), the SRH is roughly between 150 and 350 across the key stormy areas as the system move through; this should create conditions favorable for tornadoes to form, if the other ingredients come together.

test890.gif



The Lapse Rates are medium, enough to support a conditional severe weather threat. Over the SE areas of the image (SE AL, S GA, FL Panhandle), the best Lapse Rates are found during the heat of the day, so this bears watching.


test012.gif



A measure tracking the area of the hodograph (basically how curved the hodograph is) is shown below, and it seems to pinpoint several long-track supercells, particularly across northern AL and northern GA.

test009.gif


Vertically Integrated Graupel is designed to show areas of storm cores that favor intense lightning/hail. If this measure is any indication, SE AL has the best chances of powerful storm cores.

test006.gif



The Storm Mode Index is designed to predict storm mode, as the name implies, and is essentially a modified BRN. It shows a time period from the nighttime lasting ~18 hours into the afternoon on Monday of a potential discrete tornado threat.

test007.gif



Looking at the real models out there, it looks like the 12z GFS and NAM are both on board with at least a conditional severe weather threat. I wouldn't be surprised if the threat winds up being a Level 3 Enhanced risk, given the uncertainty present and the storm mode. It looks plausible that some areas may not get any rain at all from this event, which is interesting.
 
wx_guy said:
Here's latest WRF-ARW model run based on 06z GFS initial conditions, 9 km resolution, centered on Birmingham, AL.

Composite radar shows a "line" of discrete cells tracking across MS and AL.



View attachment 37363

The SBCAPE is interesting because it shows two major pushes of storm fuel -- the first into MS and western AL overnight, then a blow up across SE AL and central GA during the day on Monday.
View attachment 37364

A large portion of the area will have LCL's below 600m in the open warm sector, which favors tornado formation, conditional on other factors being present.
View attachment 37365


In the lowest part of the atmosphere (the lowest 500m), the SRH is roughly between 150 and 350 across the key stormy areas as the system move through; this should create conditions favorable for tornadoes to form, if the other ingredients come together.

View attachment 37368



The Lapse Rates are medium, enough to support a conditional severe weather threat. Over the SE areas of the image (SE AL, S GA, FL Panhandle), the best Lapse Rates are found during the heat of the day, so this bears watching.


View attachment 37369



A measure tracking the area of the hodograph (basically how curved the hodograph is) is shown below, and it seems to pinpoint several long-track supercells, particularly across northern AL and northern GA.

View attachment 37372


Vertically Integrated Graupel is designed to show areas of storm cores that favor intense lightning/hail. If this measure is any indication, SE AL has the best chances of powerful storm cores.

View attachment 37376



The Storm Mode Index is designed to predict storm mode, as the name implies, and is essentially a modified BRN. It shows a time period from the nighttime lasting ~18 hours into the afternoon on Monday of a potential discrete tornado threat.

View attachment 37378



Looking at the real models out there, it looks like the 12z GFS and NAM are both on board with at least a conditional severe weather threat. I wouldn't be surprised if the threat winds up being a Level 3 Enhanced risk, given the uncertainty present and the storm mode. It looks plausible that some areas may not get any rain at all from this event, which is interesting.
Click to expand...
This definitely continues to strike me as a weird setup. Really interested to see how kinematics shake out. The sunrise rush-hour supercell character of things (at least, taken verbatim from what GFS has been showing) reminds me a bit of the 2008 Mother's Day outbreak.
1743097680908.png
 
Key message from BMX in there afternoon update.

KEY MESSAGES...
Updated at 1243 PM CDT THU MAR 27 2025

- There is a level 2 out of 5 risk for severe storms across all
of Central Alabama late Sunday night into Monday with a threat
of tornadoes, damaging wind gusts, and large hail. The
magnitude of the tornado threat is uncertain, but there is
potential for it to increase.

&&
 
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