Severe weather risk 4/30 - 5/3

[Radtechwxman]

1 minute ago, andyhb said:

It would be better to show the trend in moisture (i.e. dTd/dt) than just the absolute values there IMO.

Here ya go

[OKStorm]

We are not expecting a good return until Monday in Oklahoma but we have had some decent return already today.  I just think it is too soon to get worried

 

[OUGrad05]

18 minutes ago, andyhb said:

It would be better to show the trend in moisture (i.e. dTd/dt) than just the absolute values there IMO.

It's all available on OK Mesonet.  

 

[andyhb]

Just now, OUGrad05 said:

It's all available on OK Mesonet.  

I know, I'm just saying it's always best to look at trends prior rather than absolute values (what was posted earlier), especially when we're referring to advective processes.

[CheeselandSkies]

Is it even worth looking at the NAM at this point? Interesting how EHIs spike dramatically from 00z to 03Z Thursday across pretty much all of OK and south-central-SE KS. Could imply something big brewing right around sunset.

[Weatherdemon]

28 minutes ago, CheeselandSkies said:

Is it even worth looking at the NAM at this point? Interesting how EHIs spike dramatically from 00z to 03Z Thursday across pretty much all of OK and south-central-SE KS. Could imply something big brewing right around sunset.

 03z NAM sounding near OKC.

Note the May 3, 1999 analog.

 

[Chicago Storm]

10 hours ago, StormChaser4Life said:

Why wouldn't you? Nothing else in the long range. And yea the setup isn't perfect but it is way better than the last one at least with better quality moisture and much better flow aloft. When you get a trough like that in May, you chase it. Lol

I'm fairly picky.

Current plan right now though is to fly into OKC tomorrow, and then chase Tue-Thur.

[Radtechwxman]

3 minutes ago, Chicago Storm said:

I'm fairly picky.

Current plan right now though is to fly into OKC tomorrow, and then chase Tue-Thur.

Good plan. You think moisture will be an issue in your opinion? This is setting up in the major drought areas and could see some mixing. Good thing is temps don't look to warm too substantially so spreads shouldn't be too bad 

[CheeselandSkies]

Models are indicating some degree of severe potential particularly Wednesday and/or Thursday evening in the upper Midwest region, although local offices seem to be downplaying it. Guess it's a wait and see for me if a local chase materializes.

[OUGrad05]

yeah its worth looking at the NAM to see its output but don't get hung up on it.  Need to be within 60hr or 48hr to start taking it seriously.  

May 3rd analog doesn't mean much at this point IMO.  Analogs won't firm up until we're within about 48hrs for the most part.  Even then, lots of moving parts, things can come off the rails quickly and we really need the 00Z euro to at least hold the line and not continue the weakening shear/flow etc.  

[Weatherdemon]

28 minutes ago, OUGrad05 said:

yeah its worth looking at the NAM to see its output but don't get hung up on it.  Need to be within 60hr or 48hr to start taking it seriously.  

May 3rd analog doesn't mean much at this point IMO.  Analogs won't firm up until we're within about 48hrs for the most part.  Even then, lots of moving parts, things can come off the rails quickly and we really need the 00Z euro to at least hold the line and not continue the weakening shear/flow etc.  

Agreed but it was interesting nonetheless.

[CheeselandSkies]

It's encouraging that we're 2-3 days prior to event time and winds from OK to the TX/LA Gulf coast are all southerly or southeasterly.

[jojo762]

18Z NAM NEST for near AMA at 7pm Monday. A 61 degree DP would be a record level surface dewpoint for April 30 if this were to verify.

[bjc0303]

This morning 12z Euro forecast looked like a somewhat decrease on overall threat, but still had one hell of an environment along and ahead of the dry line. Impressive consistency here. 

[Radtechwxman]

1 hour ago, OUGrad05 said:

yeah its worth looking at the NAM to see its output but don't get hung up on it.  Need to be within 60hr or 48hr to start taking it seriously.  

May 3rd analog doesn't mean much at this point IMO.  Analogs won't firm up until we're within about 48hrs for the most part.  Even then, lots of moving parts, things can come off the rails quickly and we really need the 00Z euro to at least hold the line and not continue the weakening shear/flow etc.  

Yea I'm hoping that was a fluke run. Euro had been so consistent to

[OUGrad05]

Yea I'm hoping that was a fluke run. Euro had been so consistent to

Euro is consistent with the overall environment but take a look at the various shear profiles and the winds directly, in particular the 850s and you will see a steady weakening. It's somewhat subtle from run to run but you can go back four or five runs and see it the trend IMO.

 

It's still a solid environment but I am a touch nervous it may continue.

 

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[garfan]

I looked at the 18Z NAM and thru 06Z Thursday it does not break much in the way of precip in Southern Kansas and much of Oklahoma. I see some capping as well on select hour forecast soundings. Anyone think, maybe severe storm coverage will be few?

[hlcater]

27 minutes ago, garfan said:

I looked at the 18Z NAM and thru 06Z Thursday it does not break much in the way of precip in Southern Kansas and much of Oklahoma. I see some capping as well on select hour forecast soundings. Anyone think, maybe severe storm coverage will be few?

NAM struggles with CI. Best used by looking at parameter space and deciding on your own whether something would initiate or not.

[jojo762]

1 hour ago, OUGrad05 said:

Euro is consistent with the overall environment but take a look at the various shear profiles and the winds directly, in particular the 850s and you will see a steady weakening. It's somewhat subtle from run to run but you can go back four or five runs and see it the trend IMO.

 

It's still a solid environment but I am a touch nervous it may continue.

 

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I've gotta say i'm a bit concerned about the overall severe threat if storms end up firing a bit early and ruining the thermodynamical environment before the lower-level kinematics really get going in the evening. Kind of like with what happened on 5/18/17 with storms forming too soon (amidst other issues). 

I believe Wednesday could very much operate like 4/14/12 did (Note: I am NOT calling for a similar number of tornadoes as that day). With supercells firing early, propagating through the northern part of the risk area before the lower-levels really start churning, then things really lighting up south of there in the late afternoon and evening. We very well may end up with several rounds of supercell both along the dryline and in the open warm sector. The big plus this event has is that mid/upper-level flow should remain at an orientation that should keep most cells discrete, so hopefully things wont get too messy.  

Regardless of if model parameterized-output has declined or not, we are still looking at a volatile setup that very much favors intense discrete supercells. The tornado threat could very well end up materializing as higher-end, put the aforementioned concerns in addition to the concerns of others, give me some pause... Inasmuch, Wednesday should be the best *obvious* chase day in a while with numerous discrete/well-spaced supercells appearing likely.

[weatherextreme]

Do you guys think that the SPC will go Moderate for day 3 outlook or stick with Enhanced ?  I'm thinking it will stay Enhanced for the day 3 update.

[Quincy]

Tomorrow is a fine line between having limited storm coverage being a net positive or detrimental to the setup, at least when one looks at the details more closely.

The 3km NAM struggles to initiate anything across the southern High Plains through Monday afternoon. Looking at point forecast soundings across the eastern OK/TX panhandles, there's little capping left by 22-00z and convective temperatures are approached or met in much of the area. The problem appears to be upper level forcing, as the southern portion of the risk zone is barely impacted by shortwave energy that glances areas farther north. Modest 12hr height falls are noted as far south as the Texas panhandle, but this weak large scale forcing (and weak convergence along the dryline) may not be sufficient to support deep convective development.

The HRRRX is not consistently running today, but it is not much better in the runs that have completed beyond 18hr. It has shown some brief storms going up between the TX panhandle and far southwestern Kansas, but I'm assuming that limited large scale forcing is precluding more intense cells/cell longevity.

Convective initiation seems more probable in far northwestern Kansas/southwestern Nebraska, near the triple point. The issue up here is that moisture will likely be limited (low to mid-50s dew-points vs upper 50s/near 60) compared to areas farther south. Wind fields above 1km AGL here look largely unidirectional as well, at least from the 3km NAM. Convection farther north along the cold front will tend to go linear very quickly.

Much of western Kansas is left is a conditional threat zone, outside of the triple point area and better moisture pooling to the south. At this point, there has been little to no support from convection allowing models to suggest any long-lived or otherwise robust convective development here.

[Radtechwxman]

What do you guys think of the NAM for Wed? It seems to be slower with the trough ejection than global models and really fires no convection till well after dark. I remember models struggling with convecting storms on 4-14-12 cuz of strong cap and late trough arrival. Not that this event will be anything like that but the late timing makes me think of it

[CheeselandSkies]

11 minutes ago, weatherextreme said:

Do you guys think that the SPC will go Moderate for day 3 outlook or stick with Enhanced ?  I'm thinking they will stay Enhanced for the day 3 update.

Probably Enhanced unless things tick upward on the 0Z models.

[Quincy]

The NAM shows fairly steady 500mb heights from 12z Wed - 00z Thu and if progression of the system trends any slower, that's only going to cast even more uncertainty on prospects for robust convective development.

4/14/12 featured a much more potent trough and even if height tendencies during that day were fairly negligible, there were sharp height falls moving into the region by early evening.

[David Reimer]

Will be chasing tomorrow in the Texas Panhandle if it looks like we can get sustained CI. Same area on Tuesday into western Oklahoma if CI looks possible, otherwise a trip up into KS (yuck) will be warranted. Still too soon to tell on Wednesday and Thursday, but I'm not that thrilled about either day at this point. The last several years have proved time and time again that 'good looking' setups often go to crap in a basket. 

Tomorrow (Monday) reminds me a bit of 4/14/17 in terms of the moisture and low-level wind fields. CI is the main question at this point, but a 'Caprock Magic' scenario certainly is possible. I'll be out there if it looks like we can get CI. Storms in progress this evening in the western Panhandle could easily leave boundaries for tomorrow. 

[Chicago Storm]

The 0z NAM not only holding slower with the ejection Wed, but also has the LLJ displaced east of the dry line.

Not a good situation if that pans out.


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[Chinook]

Regarding Tuesday: Now that we are getting into the short-range models time frame, I think this WRF-ARW represents a good middle-of-the road forecast on thunderstorm coverage and intensity on Tuesday evening.  Dew points in SE Nebraska should be 65F. Storms should initiate along a cold front in Nebraska, Iowa, and Kansas.  Supercells are a possibility in early storms. CAPE may be 1500-3000 J/kg, with 0-3km SRH in the range of 150-300 m2/s2. As usual with April-May systems, some lapse rates of 7-8C/km to  may enhance the large hail possibilities such that hail over 2" is possible.

[Crazieman]

47 minutes ago, Chicago Storm said:

The 0z NAM not only holding slower with the ejection Wed, but also has the LLJ displaced east of the dry line.

Not a good situation if that pans out.


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Good ol' reliable Wichita pouring cold water on it as well, citing conditionality.

Was hoping for a birthday tornado, central KS has been dry for years.  Chases have been pretty boring other than hail dents.

[WhiteoutWX]

I'm not going to be trusting the long range NAM for synoptic details over the GFS/Euro. While a subtle slowing trend has been evident on the global models the past couple days, they still have plenty of QPF signal, indicating initiation is not a problem.

0z GFS has moderate/strong height falls 18-0z on Wednesday afternoon, plenty of low level shear, and upper 60s/near 70 dewpoints. I'm not gonna panic yet over some slight downtick of the threat on the 12z Euro and the long range NAM out on an island.  The threat still looks fairly robust to me. 

[jojo762]

11 minutes ago, WhiteoutWX said:

I'm not going to be trusting the long range NAM for synoptic details over the GFS/Euro. While a subtle slowing trend has been evident on the global models the past couple days, they still have plenty of QPF signal, indicating initiation is not a problem.

0z GFS has moderate/strong height falls 18-0z on Wednesday afternoon, plenty of low level shear, and upper 60s/near 70 dewpoints. I'm not gonna panic yet over some slight downtick of the threat on the 12z Euro and the long range NAM out on an island.  The threat still looks fairly robust to me. 

00Z GFS looks perfectly fine. Especially for western Oklahoma, where the environment looks particularly volatile on the latest gfs. Still scattered supercells indicated amidst a moderately/strongly unstable and highly sheared atmoshere.

With that said, the NAM has proven itself time and time again to be hot garbage at 48+ hours.