Central/Western Medium-Long Range Discussion

[jojo762]

00z GFS continues to be pretty solid for sunday. Hate that the LLJ is WAY veered, but shouldn't matter too much. Solid BL-moisture, strong/moderate instability, strong deep-layer shear, and more-than-sufficient low-level shear. Best thing though? Storms **should** be discrete per model QPF output. Little concerned that BL and low-level moisture may become a bit displaced from the DL though, owing to the veered low-level flow. Also a little concerned about potential VBV issues, in relation to storm mode.

 

[andyhb]

3 minutes ago, jojo762 said:

00z GFS continues to be pretty solid for sunday. Hate that the LLJ is WAY veered, but shouldn't matter too much. Solid BL-moisture, strong/moderate instability, strong deep-layer shear, and more-than-sufficient low-level shear. Best thing though? Storms **should** be discrete per model QPF output. Little concerned that BL and low-level moisture may become a bit displaced from the DL though, owing to the veered low-level flow.

A veered low level jet to that degree would decrease convergence along the dryline and makes it harder for storms to form. Considering the forecasted EML, that would be a fairly substantial issue. If moisture is any less than forecast, that would really throw a wrench in it.

[bjc0303]

3 minutes ago, jojo762 said:

00z GFS continues to be pretty solid for sunday. Hate that the LLJ is WAY veered, but shouldn't matter too much. Solid BL-moisture, strong/moderate instability, strong deep-layer shear, and more-than-sufficient low-level shear. Best thing though? Storms **should** be discrete per model QPF output. Little concerned that BL and low-level moisture may become a bit displaced from the DL though, owing to the veered low-level flow.

ECMWF and GFS are in no agreement whatsoever on placement. ECMWF solution lends to a more S/SW or S low level jet. typical of GFS being too progressive. ECMWF also has lee cyclogenesis as expected with its wave/height field whereas GFS just has broad low pressure associated with low amplitude wave/jet aloft. EPS shows pretty good signal and I have to say I think I side with the euro/EPS. If at any point the Euro or EPS begin to trend towards the GFS, I will be concerned. I think this is a case of the GFS being too progressive with smaller waves.. as we have seen several times this spring 

 

[brettjrob]

dProg/dt on the GFS for 00z Mon shows a tendency toward a less negative tilt with the trough axis, and associated more zonal flow at H5. I already don't like low-amplitude waves this early in the season on the Plains, and this is only raising my concerns. In my experience, H85 flow as veered as what the 06/00z GFS shows verbatim along the dryline in OK is nearly a dealbreaker for meaningful tornado potential in this part of the country.

For the most part, when you have low-amplitude waves traversing a Plains dryline in the early season, the shortwave timing has to be absolutely impeccable - where you get your LLJ to back and intensify right around 21-00z. If that isn't the case, as is currently modeled Sunday, you either get (1) a cap bust, or (2) if you're fortunate enough to get CI, tornado potential is limited, even if other factors (e.g., good moisture return) are in place.

Still time for 6-12 h timing shifts, so not throwing in the towel by any means - just commenting.

[bjc0303]

4 minutes ago, brettjrob said:

dProg/dt on the GFS for 00z Mon shows a tendency toward a less negative tilt with the trough axis, and associated more zonal flow at H5. I already don't like low-amplitude waves this early in the season on the Plains, and this is only raising my concerns. In my experience, H85 flow as veered as what the 06/00z GFS shows verbatim along the dryline in OK is nearly a dealbreaker for meaningful tornado potential in this part of the country.

For the most part, when you have low-amplitude waves traversing a Plains dryline in the early season, the shortwave timing has to be absolutely impeccable - where you get your LLJ to back and intensify right around 21-00z. If that isn't the case, as is currently modeled Sunday, you either get (1) a cap bust, or (2) if you're fortunate enough to get CI, tornado potential is limited, even if other factors (e.g., good moisture return) are in place.

Still time for 6-12 h timing shifts, so not throwing in the towel by any means - just commenting.

Are we just going to ignore other guidance?

 

12z Euro seemed pretty favorable to me and its ensemble seems to back it up pretty well. No idea what individual members looked like.. GEFS still had considerable spread among members. 

They seem to be trending in opposing directions, haha.

[brettjrob]

2 minutes ago, bjc0303 said:

Are we just going to ignore other guidance?

 

12z Euro seemed pretty favorable to me and its ensemble seems to back it up pretty well. No idea what individual members looked like.. GEFS still had considerable spread among members.

Not my intention at all. Would note the GFS and Canadian have been relatively steadfast in depicting veered H85 as an issue, though. Euro has been more encouraging on several recent runs.

[bjc0303]

Just now, brettjrob said:

Not my intention at all. Would note the GFS and Canadian have been relatively steadfast in depicting veered H85 as an issue, though. Euro has been more encouraging on several recent runs.

I was mostly kidding. Agreed on GFS. Just odd to me that EPS and euro deterministic are trending to a deeper compact and negatively tilted wave while GFS holds its ground.

[bjc0303]

somewhat interesting to me looking down the line is the trend/stubbornness of SE ridge... we will probably see a brief lull in activity but thinking a return to active wx again may be faster than originally thought. 

[pbrussell]

I was (and am) planning on a sunday chase.

Worried about the cap. May just stay home. 

[brettjrob]

Unfortunately, the 12z NAM and ECMWF both now support the idea of wave timing ~6 h too early, resulting in veered and anemic flow around H85 along the dryline. Leaning more and more toward a primary large hail threat for now.

[bjc0303]

15 minutes ago, brettjrob said:

Unfortunately, the 12z NAM and ECMWF both now support the idea of wave timing ~6 h too early, resulting in veered and anemic flow around H85 along the dryline. Leaning more and more toward a primary large hail threat for now.

Starting to seem that way, although NAM and GFS exhibited a slowing trend approaching event hour (especially the GFS) with some of the waves earlier in this season...... Maybe we'll luck out? 

 

Just about ready to wave the white flag and look down the line

[Quincy]

1 hour ago, brettjrob said:

Unfortunately, the 12z NAM and ECMWF both now support the idea of wave timing ~6 h too early, resulting in veered and anemic flow around H85 along the dryline. Leaning more and more toward a primary large hail threat for now.

The lack of more turning with height seems to be the biggest red flag. Steep lapse rates are there and both the EC and NAM erode the cap by 00z. EC also favors a discrete storm mode as well. Although moisture is better than some recent events, the EC favors near 60F dews, as opposed to the more bullish NAM. This, along with veered flow/largely unidirectional wind fields aloft points toward a marginal tornado threat at best.

Mixed signals here, but a lower end severe (mainly hail) event seems most reasonable, unless things trend in another direction soon. 

Not unusual at all for early April, but not particularly impressive either. 

[David Reimer]

Sunday is crap. High signal from CIPS of severe from OK up to IA, but the tornado output is almost completely blank. Another good day to sit at home (or near it). Veered LLJ, marginal moisture return in terms of depth, and timing issues. 

[bjc0303]

notable trends on last few NAM runs: 

-westward shift of triple point and dry line. less veered sfc flow and a more N/S dry line

-greater instability owing to both a slightly higher sfc moisture fcst and now lapse rates being forecasted to approach 9 (!) K/km. 

-while features shift west, low level jet hasn't really shifted so some lessening of low level shear has occurred. It's mixed among models so we will have to see how that evolves over time. 

Overall a decent early season event if you ask me, although I live near where the dry line will most likely set up. Tor potential looks non zero but still low, but should trends continue it could be okay. 

Interestingly, this looks like a left mover fcst by the 3 km. I don't think I've seen a left mover fcst by a CAM before, or not very often at least. Encouraging to see CI. 

[bjc0303]

Latest ECMWF shows what could be a 2-day event on Easter weekend in the high plains. Sunday looks most interesting to me with the arrival of a negatively tilted trough over the southern/central Rockies. ECMWF shows QPF suggesting supercells along the dry line (by 00z MON) from western KS down through the panhandles of TX/OK. 

Pros: a solid synoptic setup on Easter weekend

Cons: Well, it is about 210 hours out...

 

ECMWF also indicates jet extension over pacific that might lead to some western US troughing into late April and early May. Waiting to see what latest ensemble guidance suggests. Pattern looks to remain fairly progressive last I saw.

[brettjrob]

00z 4 km CAMs unanimous on an intense but slightly elevated supercell streaking across south central OK tomorrow evening.

I can recall an event around this time last year with some similarities and a similar consensus (over NW OK and S KS) where the CAMs said "just kidding" by late morning the day of, so nothing's assured. The SBCINH is awfully formidable even right at 00z, and I have little doubt it will require a mesolow with localized enhanced convergence to pop off a storm at all. Fingers crossed for a nice mothership at sunset dumping some baseballs and putting on a highly visible light show for awhile after dusk.

[bjc0303]

2 hours ago, brettjrob said:

00z 4 km CAMs unanimous on an intense but slightly elevated supercell streaking across south central OK tomorrow evening.

I can recall an event around this time last year with some similarities and a similar consensus (over NW OK and S KS) where the CAMs said "just kidding" by late morning the day of, so nothing's assured. The SBCINH is awfully formidable even right at 00z, and I have little doubt it will require a mesolow with localized enhanced convergence to pop off a storm at all. Fingers crossed for a nice mothership at sunset dumping some baseballs and putting on a highly visible light show for awhile after dusk.

You're going out for this? 

 

I probably will...perks of living near the typical dry line position..

[David Reimer]

10 hours ago, bjc0303 said:

You're going out for this? 

 

I probably will...perks of living near the typical dry line position..

 

12 hours ago, brettjrob said:

00z 4 km CAMs unanimous on an intense but slightly elevated supercell streaking across south central OK tomorrow evening.

I can recall an event around this time last year with some similarities and a similar consensus (over NW OK and S KS) where the CAMs said "just kidding" by late morning the day of, so nothing's assured. The SBCINH is awfully formidable even right at 00z, and I have little doubt it will require a mesolow with localized enhanced convergence to pop off a storm at all. Fingers crossed for a nice mothership at sunset dumping some baseballs and putting on a highly visible light show for awhile after dusk.

The benefit of living in Norman is one doesn't really have to "go out" per say. Just chill at home till 3-4PM. If it looks like storms may pop, drive an hour. Otherwise, continue on your day.

[Jim Martin]

Few cells trying to develop east of Interstate 35 this hour.

[Quincy]

26 minutes ago, Jim Martin said:

Few cells trying to develop east of Interstate 35 this hour.

Those cells look to be east of the instability axis and are moving into a region with considerable CINH. Some cu is spitting off the dryline in western OK, but even there, at least some capping is holding on. 

[bjc0303]

those cells are well elevated associated with DCVA. no chance of becoming sfc based

[Jim Martin]

Cap breaking possibly?

[okiestormgeek]

Any idea when we might see the next round of significant severe weather in the central/southern plains? 

[Quincy]

1 hour ago, okiestormgeek said:

Any idea when we might see the next round of significant severe weather in the central/southern plains? 

Nothing stands out in the next 10 days. That's not to say you can't get a mesoscale event or two, or perhaps some change in the pattern, otherwise it looks like a relatively quiet mid-April stretch. 

[bjc0303]

Does seem like a pretty quiet stretch ahead. Latest EPS does suggest an extended period of southwest flow aloft towards the latter portion of April.

[WhiteoutWX]

Definitely nothing that screams outbreak in the next 7-10 days, but the GFS is at least offering some possible smaller scale setups in the southern Plains in that timeframe. Looks like Saturday, Monday, Tuesday, and Wednesday all have at least some potential in the TX-OK-KS corridor. Upper flow is lacking, especially Saturday and Monday, but there may be *just* enough mid level flow coupled with good moisture and low level shear for at least a conditional tornado risk any one of those days. One other caveat is capping may be a concern with no clearly defined waves at the moment to help provide background ascent, but maybe some subtle shortwaves will appear that could help with that as we get closer. 

[andyhb]

Positioning of subtropical ridging is going to have to change here. It's anchored too much over the central US shunting the storm track north (almost reminiscent of a late June/July-type pattern) before any shortwave can eject into the Plains. Need to get that shifted east.

So far this year, the Pacific jet has been overwhelming these western/central US ridging episodes with time. The cycles in AAM/MJO activity have been driving jet extensions generally towards the tail-end of the months. Some of the mid-range ensembles are generally indicative of this occurring again, but probably don't want that ridge to become too dominant in the meantime.

[bjc0303]

European ensemble especially shifts the ridging east particularly near/after 240 per yesterday's 12z run, but in the meantime what looks like an early summer pattern looks to prevail. Somewhat concerning to see so early on but perhaps it's only a short term thing.

 

12z model suite edit: late next week needs to be watched closely.

[bjc0303]

A little earlier than I originally thought but 00z GFS depicts a *very* potent system impacting southern plains Weds afternoon/eve. Again - next week needs close watching....

[weatherextreme]

2 hours ago, bjc0303 said:

A little earlier than I originally thought but 00z GFS depicts a *very* potent system impacting southern plains Weds afternoon/eve. Again - next week needs close watching....

Looks interesting