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Central/Western Medium-Long Range Discussion


andyhb
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Looking at medium to long-range ensembles, the signal for a potentially active pattern is really quite strong(especially given the range) and it's hard not to like what is being shown. First off, subtle system coming into the west next week will probably yield some chase worthy days with a potential lull for a few days over the weekend.

By weeks 2/3 things really get interesting, the modeled jet extension starts to come into play here and this is where that super consistent -- both run to run and model to model -- signal is located. Northern hemispheric pattern is also following a rather textbook evolution that tends to lead towards active periods for plains severe wx potential and supports this evolution. The current ridge over the Yukon/Alaska slowly retrogrades with time and ultimately ends up somewhere over Eastern Siberia. Furthermore, a ridge looks to build to a limited degree over Hawaii, with multiple strong waves crossing the pacific on a track for the western US courtesy of an active jet. Looking like the long-range could evolve into a fairly active stretch and given the range there's really quite the signal for it. It also makes sense with AAM/GWO transition but the mechanisms of how AAM and tropical forcing mettle with patterns is not my cup of tea (though to be fair none of this hemispheric stuff really is). One last thing is that the AAM/GWO transition is not as amplified as last year which might mean that the resulting pattern is not as amplified (someone correct if wrong), and if that is the case, combined with an Actually Present EML™, could set up a really nice chasing period. I'm obviously very optimistic.

However, one thing that does put me on hold here is the tendency for low latitude troughing to show up on some ensemble runs. The gulf is cooking this year so whether or not this actually has any significant effect with such a strong gulf and being in the second half of May remains to be seen, but it is there off and on and is worth noting.

But for now, let's just treat ourselves with this.

ba60cbcef7bbca0020589e7184417d05.png

 

18z GEFS pacific pattern gif just because:
 

d0301a7c9356e572bf4dddf143d8c048.gif

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  • 2 weeks later...

Looking like those long range ensembles from May 8th are going to verify. Looking at a multi-day period starting mid-week with severe potential along a lengthy portion of the high plains... followed by what will likely be several days of severe storm opportunities from Thursday-Sunday in the central and southern plains. Models diverge a bit on details and days of interest, so it’s hard to nail down many specifics. Good chance we don’t see any days delineated in tonight’s D4-8. 
 

For example, though, the GFS is more aggressive with Thursday and Saturday, while the Euro is aggressive with Thursday (in an area much further west than the GFS) and on Sunday.

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  • 10 months later...

Nebulous details of moisture quality, shortwave timing and orientation, as well as low/mid-level temps aside, it sure looks like we could see a legit threat of severe weather somewhere across the central/southern plains mid/late-next week as moisture begins to advect northward starting as early as Sunday and a trough develops out west.

Beyond that, things probably get fairly boring for a bit as NW/zonal flow becomes dominant across most of the country east of the Rockies.

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2 hours ago, jojo762 said:

Nebulous details of moisture quality, shortwave timing and orientation, as well as low/mid-level temps aside, it sure looks like we could see a legit threat of severe weather somewhere across the central/southern plains mid/late-next week as moisture begins to advect northward starting as early as Sunday and a trough develops out west.

Beyond that, things probably get fairly boring for a bit as NW/zonal flow becomes dominant across most of the country east of the Rockies.

Well, the above few posts from last year didn't exactly age well.

It's still early season, at this point I'm just happy we're not locking into an extended winter-like pattern as we roll into April.

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17 minutes ago, CheeselandSkies said:

Well, the above few posts from last year didn't exactly age well.

It's still early season, at this point I'm just happy we're not locking into an extended winter-like pattern as we roll into April.

Eh, they aged okay but definitely not great. Late May last year wasn't exactly blockbuster for tornadoes, but there were many chaseable days -- that's all I can really ask for. That Wednesday Andy referenced turned out to be a frustrating day in the TX panhandle/western OK (drove from E KS for what amounting to a bunch of nice looking turkey towers) but some folks got some good structure in southwestern Oklahoma later in the evening.

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30 minutes ago, jojo762 said:

Eh, they aged okay but definitely not great. Late May last year wasn't exactly blockbuster for tornadoes, but there were many chaseable days -- that's all I can really ask for. That Wednesday Andy referenced turned out to be a frustrating day in the TX panhandle/western OK (drove from E KS for what amounting to a bunch of nice looking turkey towers) but some folks got some good structure in southwestern Oklahoma later in the evening.

The problem for me is, being from Wisconsin and of somewhat limited means, I need higher-ceiling, multi-day setups to take time off work and drive 15-20 hours out to the Southern/Western Plains (not that it was happening last year anyway with COVID). May 20, 2019 was a perfect example, although it ended up sucking anyway (got on the Mangum cell well before it produced, but got caught up in the traffic jam and couldn't see the tornado, and nothing about that day was photogenic in the slightest what with the stupid wildfire haze).

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Some better agreement by the models today about Wednesday being "the day" for the system to eject into the plains. Admittedly the current forecast guidance would not exactly yield a chaseable setup with questionable moisture, veered/unsubstantial low-levels and potential for a strong cap. Personally not sure that models have a good grasp yet on what to do with this lead wave (that basically did not exist on the Euro until last night's 00z run).

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14 hours ago, jojo762 said:

Some better agreement by the models today about Wednesday being "the day" for the system to eject into the plains. Admittedly the current forecast guidance would not exactly yield a chaseable setup with questionable moisture, veered/unsubstantial low-levels and potential for a strong cap. Personally not sure that models have a good grasp yet on what to do with this lead wave (that basically did not exist on the Euro until last night's 00z run).

The only thing that seems to be guaranteed is that we're going to be dealing with a worsening Spring drought.

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On Friday evening, a dryline should exist in Texas, with a fast-moving cold front coming into Oklahoma. Models have 65-70 dew points in eastern Texas. There seems to be some potential for over 3000 J/kg of CAPE and 500mb winds of 50 kt in eastern Texas.

tO2fUPR.png

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11 hours ago, Chinook said:

On Friday evening, a dryline should exist in Texas, with a fast-moving cold front coming into Oklahoma. Models have 65-70 dew points in eastern Texas. There seems to be some potential for over 3000 J/kg of CAPE and 500mb winds of 50 kt in eastern Texas.

tO2fUPR.png

It has potential.

Highly conditional setup this far west though. 

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Extended range guidance looks *very* rough for OK/KS... Some potential for a setup on Friday in Texas as @Chinook alluded to, but still inconsistency in modeling. Looking like we will have a strong STJ influence across the northern Gulf coast for quite sometime, which clearly is not favorable for moisture return into the plains. Ultimately there will probably be some SLGT-risk caliber setups in TX the next 10-14 days, but probably nothing superbly obvious. FWIW (which isn't much), latest long-range fantasy land guidance suggest it could be well into May until we see another favorable SW-flow setup in the Plains -- yikes. 

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1 hour ago, stormdragonwx said:

As I mentioned in another post, this season feels quite a bit like 2013. I'm betting it will blow up in the last two weeks of May going into June.

I'd take it... 2013 was VERY boring until the last two weeks in May -- which saw NINE Moderate risk days across the Plains, with some very notable tornadoes thrown in there: Our last official EF5 tornado, in Moore, and the El Reno 302mph, 2.6 mile wide tornado to name a couple.

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22 hours ago, jojo762 said:

I'd take it... 2013 was VERY boring until the last two weeks in May -- which saw NINE Moderate risk days across the Plains, with some very notable tornadoes thrown in there: Our last official EF5 tornado, in Moore, and the El Reno 302mph, 2.6 mile wide tornado to name a couple.

The two  E5's    made the whole season in itself .  I don't think we need another of those .    Just give a bunch of E2-3's    

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On 4/11/2021 at 9:01 AM, jojo762 said:

Extended range guidance looks *very* rough for OK/KS... Some potential for a setup on Friday in Texas as @Chinook alluded to, but still inconsistency in modeling. Looking like we will have a strong STJ influence across the northern Gulf coast for quite sometime, which clearly is not favorable for moisture return into the plains. Ultimately there will probably be some SLGT-risk caliber setups in TX the next 10-14 days, but probably nothing superbly obvious. FWIW (which isn't much), latest long-range fantasy land guidance suggest it could be well into May until we see another favorable SW-flow setup in the Plains -- yikes. 

The thing that I "alluded to" already happened on 4/9-4/10, and I haven't posted about other upcoming events.

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17 hours ago, jojo762 said:

General idea in mid/long-range guidance is that there could be a solid trough in the southern Plains next week... Not much agreement on timing or degree of moisture ATTM, but at least its something to watch?

There may also be some action in the central plains towards the last few days in April.

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23 minutes ago, stormdragonwx said:

Soooo.... do we dare talk about this yet? Yes you are reading these graphics correctly. Possible snow on the GFS and Euro showing up next week. :blink:

Screenshot_20210415-214848.png

Screenshot_20210415-215045.png

Seem some talk about this year being similar to 2013.... well 2013 had a decent late season snow event impacting some of the areas above. 

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Today's (4/20) 12Z ECMWF definitely has the look of a classic Plains outbreak for next Tuesday (4/27). GFS/GGEM also show a powerful system, but their solutions are more amplified, which would likely lead to a messier event if it happened to verify that way. 

Aside from the trough evolution, a big key with next week's system will be the quality of moisture return. That will depend in part on how far south this weekend's system can push a cold front through the Gulf. The ECMWF (and other guidance) has varied from run to run regarding moisture return for early next week, so probably premature to say that it is "locking onto" anything yet. Previous runs of the ECMWF have struggled to get low 60s dewpoints north of OK next Tuesday, whereas today's 12Z run has low 60s dewpoints into IA/MN and mid/upper 60s into KS/OK. If the juicier solution becomes a trend, then next week's potential event becomes a lot more interesting. 

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