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

NAM and other mesoscale/short range ensemble forecasts continue to advertise a more significant threat than the globals for Wednesday. 2 rounds on the latest NAM. One, with early morning round of convection with the LLJ kicking in with the warm front, and a later round with the effective dry line/cold front. NAM is likely a bit overdone on thermos, but low level wind fields are much improved.

My question, who do we go with?
 
NAM showing some juicy LRs in the afternoon.

AqicooMl.jpg
 
I just saw the 18z NAM and it does move out the morning warm frontal convection awfully quick and if that verifies, the afternoon could get quite interesting over a large area
 
Kory said:
NAM and other mesoscale/short range ensemble forecasts continue to advertise a more significant threat than the globals for Wednesday. 2 rounds on the latest NAM. One, with early morning round of convection with the LLJ kicking in with the warm front, and a later round with the effective dry line/cold front. NAM is likely a bit overdone on thermos, but low level wind fields are much improved.

My question, who do we go with?
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Yeah the NAM from 12z-21z or so looks like trouble. Definite threat of supercells and tornadoes in that round with both 0-1km and 0-3km helicity over 250 and both high cape and lapse rates. That line with the front is no slouch either.
 
GTWXAlum said:
I just saw the 18z NAM and it does move out the morning warm frontal convection awfully quick and if that verifies, the afternoon could get quite interesting over a large area
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That morning round looks quite potent as well. This isn't going to be your organized cold pool MCS type of convection. This will be scattered storm cluster/supercells and then strong LLJ response ensures the afternoon is round #2 for severe wx.
 
The vertical velocity is one of my favorite tools to see what the model is seeing. This is VV at 700mb 15z.

weather-816572.jpg
 
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ARCC said:
The sounding for near BHM same time as image above.

nam_2017040318_045_33.29--86.6.png
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very nice sounding but we see that all the time on the NAM. [emoji1] Wed will be interesting I think. The only thing Im cofident is we will see some type of severe wx. I know others have said the morning convection clears out in a hurry but with the way things have gone recently you have to wonder how much that will limit severe wx. Interesting and difficult forecast.

Sent from my SM-G935P using TalkWeather mobile app
 
darkskys25 said:
very nice sounding but we see that all the time on the NAM. [emoji1] Wed will be interesting I think. The only thing Im cofident is we will see some type of severe wx. I know others have said the morning convection clears out in a hurry but with the way things have gone recently you have to wonder how much that will limit severe wx. Interesting and difficult forecast.

Sent from my SM-G935P using TalkWeather mobile app
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I think the big question in my mind is how fast do the winds go unidirectional. The 18z GFS also shows SBCapes up to 3000, it just veers the wind column that much faster. Logic says as we all talked about this morning for them to stay backed longer than shown, but who knows.
 
darkskys25 said:
very nice sounding but we see that all the time on the NAM. [emoji1] Wed will be interesting I think. The only thing Im cofident is we will see some type of severe wx. I know others have said the morning convection clears out in a hurry but with the way things have gone recently you have to wonder how much that will limit severe wx. Interesting and difficult forecast.

Sent from my SM-G935P using TalkWeather mobile app
Click to expand...
It might be helpful to discuss how this situation is different compared to what we have seen this year. To begin, I do not see any kind of mcs along the coast. What develops down there moves north and then quickly east-I am guessing that is the mid level dry air arriving. Also, although not as much as in previous runs, this s/w is a little more contained, compact and less spread out and messy that we usually see along with strong hieght falls near the coast.
 
What's your take for North AL for the afternoon round? Trying to decide whether to keep a dentist appointment that could have us out from about 1-5pm depending on how long it takes or reschedule for another day.
 
Parysa said:
What's your take for North AL for the afternoon round? Trying to decide whether to keep a dentist appointment that could have us out from about 1-5pm depending on how long it takes or reschedule for another day.
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I wouldnt want to be anywhere on Wednesday afternoon that might put me or my children in harm's way. Unless it is an extreme emergency, I'd postpone. Vehicles are the last place you want to be with a strong or violent tornado approaching.
 
The 18z models actually made me shake.........they looked that scary. I even saw a couple 00z 04/04/74 Alabama analogs for ATL at 18z WED :o
 
I'm not comparing in any way, but what happened 4/27/11 that allowed for both morning and afternoon tornadoes? Would typically think that after the morning convection, that would have stabilized things for the afternoon. But as we all know, that didn't happen.....
 
PerryW said:
The 18z models actually made me shake.........they looked that scary. I even saw a couple 00z 04/04/74 Alabama analogs for ATL at 18z WED :eek:
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Yeah some very impressive soundings off of NAM12km/3km and the GFS. They are coming in line with the Euro on timing too with the front coming through between 21-03Z.
 
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