April 20-23 Plains severe threats

[Quincy]

Wednesday: Localized early season NW flow setup, focused on northeastern Oklahoma/southeastern Kansas. Would expect at least isolated supercell development near the I-44 corridor. 

Thursday: Another localized threat, in the general vicinity of Kansas. Can’t say I’ve looked at it too closely as there isn’t a strong signal, since heights look to be neutral or slightly rising. 

Friday: A potentially more significant severe thunderstorm threat, centered around Kansas/Nebraska, as a trough swings east out of the Rockies. 

Edit: Added Saturday since SPC has highlighted a 15% risk area including parts of Kansas. 

[NCIWxGuy]

Friday is a potentially very interesting day on the High Plains. At first glance, it has many of the looks of an extensive dryline tornado event from McCook to Lubbock with another appealing triple point play into the Sandhills, but wave timing and other factors will probably preclude this caliber of event. I'm particularly interested to see if we can pull something off here in the TX Panhandle, but am worried that the NAMs are undermixing down the dryline and overdoing the moisture. Capping isn't progged to be particularly strong down here, a nice change of pace given the extreme drought. Moisture and CI aside, the ceiling is potentially high should things align sufficiently. A slightly earlier wave timing would aid things here *a lot*. Otherwise, I'm hopeful for somewhat late CI with a couple supercells maturing just before the sunset hour can work its magic.

[stormdragonwx]

Intrigued that the SPC upped the probs slightly for today. Maybe it's because I'm cynical but it feels too cool outside (52 here in Fayetteville, AR at 11:30) and there's too much considerable cloud cover lingering considering its almost noon over much of the highlighted area. We would have to have some rapid clearing and heating to destabilize the area for any supercells to form this afternoon. Even for parts of Eastern Oklahoma where the 5% is. Thoughts?

[Quincy]

1 hour ago, stormdragonwx said:

Intrigued that the SPC upped the probs slightly for today. Maybe it's because I'm cynical but it feels too cool outside (52 here in Fayetteville, AR at 11:30) and there's too much considerable cloud cover lingering considering its almost noon over much of the highlighted area. We would have to have some rapid clearing and heating to destabilize the area for any supercells to form this afternoon. Even for parts of Eastern Oklahoma where the 5% is. Thoughts?

I’ve felt this way before and was proven wrong when a potent, compact system resulting in rapid thermodynamic recovery across Oklahoma. 

Note 3hr dew-point increases of 4-7 F are common in eastern/central Oklahoma. Mesoanalysis shows convective inhibition eroding and satellite imagery indicates rapid clearing and surface heating east of the dryline. Temperatures have reached the lower 80s already, on the east side of the dryline  

With that said, storm coverage and intensity is still a big question mark, given weak large scale forcing and inconsistent convection allowing model signals. 63-65 F dew-points along/just east of I-35 in north-central Oklahoma catches my attention.

Another nuanced setup in Oklahoma this season… Nearly 50/50 odds, in my mind, of the following solutions today:

1. Attempts at convective initiation end up failing, somewhat similar to last Friday. 

2. One or two sustained storms go up in northeastern Oklahoma and become supercells for a couple of hours.

Watch two areas, near the surface low in far southeastern Kansas, as well as a quasi triple point along the dryline, somewhere near or just southeast of Tulsa. 

[Quincy]

Short-term update:

Trends appear to be favoring storm initiation, possibly soon. Satellite imagery shows a growing cumulus field along the dryline in south-central Oklahoma. Not totally surprising with rapid heating and obs of 87/65 at Ardmore and 87/64 at Pauls Valley. 

In general, the more aggressive moisture recovery progs from the 3km NAM are verifying, with a swath of 66-69F dew-points across eastern Oklahoma, immediately ahead of the dryline.

We’re in the nowcast phase, but even the latest SREF featured higher probabilities of convective initiation between 21-00z, compared to earlier runs.

Forecast soundings show very favorable wind profiles for supercells, with NW flow aloft, backing to S near the surface. Mesoanalysis indicates >2000 J/kg MLCAPE with increasing 0-3km instability over the next couple of hours. Forecast hodographs by 23-00z show sickle shaped low level hodographs, which would be very favorable for tornadoes. Even conditionally supportive for a strong tornado.

It’s getting very interesting. I would be shocked if there’s not a mesoscale discussion issued shortly to outline the threat. 

[Chinook]

The models show almost no precipitation in the Plains for tonight and tomorrow. For Friday, the NAM shows a high amount of capping pretty far west, possibly up to the dryline. The GFS shows high LCLs, but lower capping. Yes, there will be a strong low pressure system, but the only thing really good is 0-3km shear. So it kind of stinks unless we see some reason to think there will be higher chances of thunderstorms.

[Quincy]

So close, yet so far away today. A few showers initiated, but couldn’t take off. Now wondering if drought conditions on the high plains might be the tipping point to sway more marginal threats (Thursday/Friday) into the “no dice” category. 

[stormdragonwx]

Yeahhhh as I feared, calling it a bust.

[Chinook]

Now the FV3, WRF-NSSL, and WRF-ARW have some convection on Friday (48 hours)

[Quincy]

Today has some similarities to yesterday. Setup is conditionally favorable for isolated supercells, but CAM support is inconsistent and mixed. Upper level support is weak at best, with neutral or slightly rising height tendencies.

This time, the threat may exist along the dryline in western Oklahoma and a bit farther north into SW/central Kansas, near the warm front and triple point. 

I’ll probably be lured out again, since it’s only a three hour drive, but the odds of seeing a storm are probably in the 20-30% range.

[NCIWxGuy]

Was becoming fairly pessimistic about Friday given the HRRR, but I'm beginning to wonder if it's overmixing off the dryline. Most other CAMs, including the 00z WRFs, not only keep dewpoints in the upper 50s to low 60s but also initiate supercells in the Panhandle. Feels like a moderately high ceiling, low floor scenario between Lubbock and Liberal, KS (for reachable areas on my end) for a post-00z show, although potential certainly extends further north as well. 

[Quincy]

Encountered several supercells in southwestern Kansas early this evening. What a rebound after yesterday’s flop.

 

[NCIWxGuy]

Not sure what to say about the 00z HREF other than, a) the variability in PBL mixing across members probably has massive implications on the tornado threat tomorrow, and b) woof.

[MNstorms]

Well okay then HRRR. 10-15F warming than the NAM 3k and 5-10F higher dew points makes Saturday look interesting but it's far out.

 

EDIT: RAP is closer to the HRRR as well.

[Chinook]

This will summarize some of the things happening. The SPC has kept the enhanced risk relatively similar to the most recent one. The Day-2 outlook is a slight risk from Oklahoma to Minnesota (contrary to what is being shown here on the right) Then there's just a huge blizzard in the north and a high wind warning/extreme fire behavior in the south.

[MNstorms]

Well that sucks.

 

 

[Powerball]

It's highly conditional obviously (mostly depending on how tonight's convection evolves), but I wouldn't sleep on the severe weather potential tomorrow in DFW either. The soundings are looking decent (no cap, solid lapse rates, modest low-level shear, etc.), even though none of the models show much activity due to nebulous forcing.  

I wouldn't be surprised to see a slight risk area from the SPC either.

 

 

[Chinook]

Quite a bit of hail/wind activity near the dryline yesterday

[SmokeEater]

TW OKC, rotation quickly ramping up.

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[Chinook]

Some broad rotation has been in the areas of SW Oklahoma city for a while. I don't believe there have been any reports of tornadoes yet.

[Chinook]

There are about 5 large severe storms going in Oklahoma, all without too many storm reports that I have seen. There may be some hail reports that are not on the SPC database yet.

 

3D view of storm near Blanchard, OK, with OKC storm in the distance

[Quincy]

2 hours ago, Chinook said:

Some broad rotation has been in the areas of SW Oklahoma city for a while. I don't believe there have been any reports of tornadoes yet.

Took this photo just a short time before this radar collage. Chased the storm through the south side of OKC. Very rain wrapped, but don’t believe there was a tornado. 

 

[Powerball]

22 hours ago, Powerball said:

It's highly conditional obviously (mostly depending on how tonight's convection evolves), but I wouldn't sleep on the severe weather potential tomorrow in DFW either. The soundings are looking decent (no cap, solid lapse rates, modest low-level shear, etc.), even though none of the models show much activity due to nebulous forcing.  

I wouldn't be surprised to see a slight risk area from the SPC either.

 

 

SPC has put the NW half of DFW under the slight risk area in the latest outlook.

12z HRRR sounding doesn't look too shabby either.

 

[Powerball]

Latest Hi-Res models are all bringing organized convection into DFW (mainly areas north of I-20) this evening.

 

[Powerball]

And speak of the devil, now there's a Severe Thunderstorm Watch until 6pm for the northern suburbs of DFW:

 

[Powerball]