Severe WX Severe Weather Threat 4/5/17-4/6/17

GA always overpreforms in low cape high shear events. And shear appears to be in abundance tomorrow....
 
ARCC said:
No you are correct and it's been a part of the discussion for days. The thing is when you have explosive instability it can counter act low helicity, just as very high helicity can counter act low cape in winter time systems. In this environment 200-300 helicity is plenty to put down long track tornadoes.

Another thing is some of the models may be veering the winds too much. Don't be surprised to see the winds back toward the dry line.
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Yep. Last night I noticed the exact same thing. Can the instability come in a bit faster or can we see the higher SRH stick around a little bit longer? Time will tell, but I'm onboard with there being a decent enough window of overlap with plenty of CAPE and enough helicity to support long track tornadoes.

If one or both occur then there's nothing really holding this back. At least in Alabama, I fear the morning convection won't be enough to dampen higher instability later in the day. In fact, as has been alluded to, you could have some boundaries left hanging that could help overcome weaker SRH values.
 
ARCC said:
No you are correct and it's been a part of the discussion for days. The thing is when you have explosive instability it can counter act low helicity, just as very high helicity can counter act low cape in winter time systems. In this environment 200-300 helicity is plenty to put down long track tornadoes.

Another thing is some of the models may be veering the winds too much. Don't be surprised to see the winds back toward the dry line.
Click to expand...

Agree on both points. Plus with the kind of unstable environment we should have tomorrow, even if shear overall isn't extremely high, any kind of boundary that could locally enhance helicity can make a huge difference.
 
https://www.pscp.tv/w/1OwxWPVowDWKQ

Just an amazingly scary video from NWS Birmingham. This briefing got my attention more than anything. The tone and tenor of this from a well-respected office and group of mets really is sobering. You will see a big media ramp up in the urgency of this event in the next 12 hours. This is why schools are already announcing closing. I have not seen a video like this from BMX. It is a must watch and another is coming this afternoon. Great job BMX!
 
After watching that video I think they are going to need to pull that moderate risk north as well
 
Chris3024 said:
Do y'all foresee the moderate risk being expanded northwestward over time?
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I would be shocked if it wasn't expanded a bit to the north and west. I'd say most of Alabama will be covered by at least a moderate risk tomorrow. If SPC pulls a trigger on a "high risk" I could see that not happening until there is more certainty about the morning convection, the dryline in MS firing off storms, and if there is more of a window of overlap between high CAPE and SRH. I would expect at some point tomorrow that portions of Alabama will be under a high risk. This evening should provide more clarity about the threat, and then the SPC forecast tomorrow should incorporate what we learn this evening/
 
It situations like this that irks me that the word "moderate" is used to define risk. It was good when you had three risk levels, but now with five it needs to be renamed "Significant" to properly note a level "four" risk.
 
ARCC said:
It situations like this that irks me that the word "moderate" is used to define risk. It was good when you had three risk levels, but now with five it needs to be renamed "Significant" to properly note a level "four" risk.
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Yeah to a non weather geek moderate doesn't sound like the very serious threat that it is.
 
ARCC said:
It situations like this that irks me that the word "moderate" is used to define risk. It was good when you had three risk levels, but now with five it needs to be renamed "Significant" to properly note a level "four" risk.
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To someone not into weather, I have to wonder if "enhanced" actually sounds worse than "moderate."
 
ARCC said:
It situations like this that irks me that the word "moderate" is used to define risk. It was good when you had three risk levels, but now with five it needs to be renamed "Significant" to properly note a level "four" risk.
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Yeah, I've run into the same problem trying to explain the five-tiered system to people. I understand the purpose of the five-tiered system and personally find it useful, but I think the three-tiered system was a lot less ambiguous and confusing for people who don't follow such things closely.
 
I'm in Mobile and can't figure out when or how bad it might get down here? Our street FLOODS and I need to prepare. Thx!


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FFC:

...Significant Severe Weather Outbreak Expected on Wednesday...

While today's warm and sunny weather provided a brief respite from
the stormy weather, this break will be coming to an abrupt end
on Wednesday. A strong storm system currently over the Plains will
bring widespread thunderstorms to the CWA on Wednesday, many of
which will become severe.

By early Wednesday morning a warm front will be rapidly moving
northward into the area ushering in Gulf moisture. The first
thunderstorms of the day are expected to form along this northward-
advancing warm front during the morning hours. Any thunderstorms
that form during this time frame may become severe. Large hail will
be possible with any elevated activity north of the front while
damaging winds and tornadoes would be possible with thunderstorms
forming along and just south of the warm front in the warm sector.

As we approach midday into the early afternoon, additional
widespread thunderstorm development is expected across the CWA with
a strong upper jet and associated divergence aloft as well as ample
instability in place across the warm sector. Forecast
SBCAPE values in the 2000-3000 J/kg range are anticipated, which
if realized will provide plenty of fuel for these rapidly developing
thunderstorms. Impressive shear (for example, >50 knots of 0-6km
bulk shear) will also be in place. All of this is to say that an
appreciable severe thunderstorm outbreak is expected with tornadoes,
damaging winds, and large hail all increasingly likely. The
possibility for strong/long-track tornadoes will exist with any
discrete supercells that form.

With such a moist environment in place, heavy rainfall can also be
expected in these thunderstorms. At this point, expected rainfall
totals are not high enough to warrant widespread flooding
concerns, but localized issues will be possible. See the hydrology
section below for further details.

The threat for severe thunderstorms will continue ahead of the
approaching cold front through the evening. As the cold front
finally begins to clear parts of the area mid-to-late evening, the
severe threat will end from west to east.
 
Forbes just put out torcon readings out! 5,6,7 for parts of AL TN GA KY!
 
18z 3k NAM has slowed the system down, looks pretty nasty for most of the SE

refcmp_uh001h.us_state_vse.png
 
Psalm 148:8 said:
Still in hopes of things just not coming perfectly together....anyone got the latest model data from the NAM or others?
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I managed to get ahold of WxBell and worked with them to get their NAM and WRF feeds fixed.

It's looking very nasty. At least 13 individual cells have a sigtor index of 6+ from very high shear and capes in the 2-4k range.
Many long tracked supercells.
 
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