Severe Weather April 27-28th 2021

[cheese007]

[Joshua D Wells]

This year's storm season for Oklahoma has gotten off to a slow start, so it's difficult not to become excited. The ECMWF is hinting at something ominous. Forecast soundings across the warm sector are throwing out numerous PDS TORs. For the time being, however, the GFS is looking less than favorable for an upper end severe weather event. I'd like to see more consistency between the two models before I start taking this event seriously. That being said, a 15% threat area on day 7, with the potential for greater probabilities introduced in future outlooks is definitely something to raise an eyebrow at. 

No predictions at this point, but definitely worth keeping a very close eye on.

[RocketWX]

I'm right there with you on the difficulty of not getting excited. It has been historically slow in regards to severe weather near Wichita over the past year. I think Wichita NWS only issued 1 or 2 tornado warnings in the past year! This could be the first significant threat in this area in quite some time. As you mentioned, the Euro is certainly the more ominous solution as of now. While still a week out, I do find it interesting that all the local forecast discussions have mentioned the "potential" for a robust severe threat, combined with the already outlined 15% risk from Storm Prediction Center. From reading their forecasts they tend to be leaning toward the Euro solution. Just following models more closely the last few days, I'd agree that the GFS seems to be trending toward the Euro more so than the other way around. Early in the game, but I'm excited just to have a potential event to track the next few days!

[Powerball]

We're going to need that trough to slow down (like the 00z GFS / GGEM / EURO show) for things to work out along a ICT-OKC-DFW line. Otherwise, we're looking at yet another Dixie Alley special.

Unfortunately, models seem to underestimate how progressive the upper flow is in the medium/long term, so I'm skeptical they won't trend faster as we get closer in. 

But it's definitely the best looking potential we've had all season, FWIW.

[jojo762]

00z ECMWF last night continued to show a highly volatile setup from NE KS into western OK and down into TX. 

From a synoptic-scale it really does not get much more obvious than this. 

Euro depicts the 70-80kt mid-level jet core impinging across the dryline by 00z with a 40-50kt southerly LLJ east of the dryline. The warm-sector on the euro is quite expansive, characterized mostly by mid-60s dewpoints and strong instability.

Parts of the dryline are plagued by strong CINh, and this is well seen in the euro QPF fields hinting at limited coverage along the dryline in OK and TX and coldfront in KS.

 

This would not qualify as a true write-up about the 00z Euro if it did not feature at least one cherry-picked, "eye candy" sounding. (roughly halfway between Woodward and Elk City)

[CheeselandSkies]

11 minutes ago, jojo762 said:

00z ECMWF last night continued to show a highly volatile setup from NE KS into western OK and down into TX. 

From a synoptic-scale it really does not get much more obvious than this. 

Euro depicts the 70-80kt mid-level jet core impinging across the dryline by 00z with a 40-50kt southerly LLJ east of the dryline. The warm-sector on the euro is quite expansive, characterized mostly by mid-60s dewpoints and strong instability.

Parts of the dryline are plagued by strong CINh, and this is well seen in the euro QPF fields hinting at limited coverage along the dryline in OK and TX and coldfront in KS.

 

This would not qualify as a true write-up about the 00z Euro if it did not feature at least one cherry-picked, "eye candy" sounding. (roughly halfway between Woodward and Elk City)

Since I do not pay to access the EURO soundings on Pivotal, my analysis has been limited to the GFS which has been intent on showing a very deep trough with strongly meridional 500mb flow, and a more subdued ceiling for the event as a result. The Euro also appears to show a secondary surface low in SE NE with a warm front extending into Iowa (and the GFS, for all its flaws with the setup as portrayed, has been consistently showing some of the strongest warm sector instability over N IL/WI/MN/IA), so it could be a potential regional chase for me since I get out of work at noon Tuesday and have Wednesday off.

[radarman]

Maybe an event where the dryline progresses a certain amount on Tuesday and then sloshes back west overnight before pushing through on Weds?  Or the more common discrete (and conditional) early to linear overnight.

Either way looks potent.

[thunderbird12]

GFS is now much faster compared to the rest of the global models. Today's (4/22) 12Z ECMWF continues to trend slower with the trough, though it still shows higher-end potential for Tuesday. UKMET and Canadian have slowed down so much that the main event (if there is one) would be on Wednesday, with hardly any threat (in their solutions) on Tuesday. 

[OKTWISTER]

The NWS Tulsa is backing way off on the severe weather next week up in the Tulsa area. Looks like timing and the system going further south really cut back the threat. 

 

NWS TULSA

DISCUSSION...
A few showers will linger across the area this morning as an upper
system departs to the east, with the greatest coverage of showers
across far eastern Oklahoma and northwest Arkansas. Skies will
clear this afternoon, but breezy northerly winds will keep
temperatures below the seasonal normals.

Strong southerly winds return Sunday through Tuesday, which will
result in temperatures warming to much above normal levels early
next week. Recent trends in the data suggest a slower, more
southerly track to the next storm system that will affect the area
during the middle part of next week. While there certainly remains
some severe weather potential with this system, heavy rainfall and
flash flooding may eventually become a bigger concern given the
slower southerly track. Several rounds of showers and storms will
likely occur from late Tuesday night through Thursday before this
system finally exits our area, bringing drier weather with near
seasonable temperatures heading into next weekend.

Adjusted the National Blend of Models pops and temperatures some
with the midweek system to account for the slower timing, but
otherwise stayed fairly close to the NBM forecast.

 

[weatherextreme]

SPC in the latest update showed a major shift to the west

 

 

 

[stormdragonwx]

 

1 hour ago, weatherextreme said:

SPC in the latest update showed a major shift to the west

 

 

 

Interesting. Right back in the same area as yesterday's event. Though I somehow doubt we will see a repeat performance. Either way I'd love to get redemption for having to miss yesterday. 

[cheese007]

Seems like there is talk of the original threat area getting severe weather on D5 instead? 

[Powerball]

5 hours ago, cheese007 said:

Seems like there is talk of the original threat area getting severe weather on D5 instead? 

Potentially.

Models are still struggling with how progressive the trough will be. 

[CheeselandSkies]

1 hour ago, Powerball said:

Potentially.

Models are still struggling with how progressive the trough will be. 

Tuesday evening is within NAM range now, it joins how the GFS has been for quite a while with this system in portraying not much CAPE despite a broad warm/moist sector. Ironically it likewise shows one of the more unstable areas being over MBY, while the local forecast office and broadcast mets have not sounded impressed on severe potential around here.

[yoda]

Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0223 AM CDT Sun Apr 25 2021

   Valid 271200Z - 281200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
   WEST TX AND THE TX PANHANDLE INTO WESTERN/CENTRAL OK AND
   SOUTH-CENTRAL KS....

   ...SUMMARY...
   Severe thunderstorms are possible Tuesday afternoon through Tuesday
   night from portions of West Texas and the Texas Panhandle into
   western/central Oklahoma and south-central Kansas.

   ...Synopsis and Discussion...
   A deep upper trough is forecast to be in place over the western
   CONUS early Tuesday morning. Strong mid/upper level flow will extend
   throughout the basal portion of this trough, beginning the period
   arced from off the central CA coast across northern Mexico and into
   the southern High Plains. This upper trough is expected to make
   modest eastward progress throughout the day while an embedded
   shortwave trough ejects over northern/central NM into eastern
   CO/western KS. This evolution will help spread the strong mid-level
   flow over much of the southern and central Plains. 

   The surface pattern early Tuesday will likely feature a low near the
   central NE/KS border, with a dryline extending south-southwestward
   across central KS and northwest OK, and into the TX Panhandle. This
   dryline will likely remain in place, sharpening throughout the day
   as moderate low-level moisture advection continues to its
   east/southeast. Low-level convergence into this boundary combined
   with increasing large-scale ascent attendant to the approaching
   shortwave is forecast to result in convective initiation amid a
   diurnally destabilizing air mass. Some uncertainty exists regarding
   storm coverage, largely as a result of unknown cap strength and
   quality of the moisture return. Even so, environmental conditions
   support a predominantly supercell mode with any storms that do
   develop. All severe hazards are possible, including very large hail
   and tornadoes. 

   Central High Plains surface cyclogenesis will likely cause a
   westward retreat of the dryline during the evening. At the same
   time, a strengthening low-level jet will increase warm-air advection
   across the boundary. These factors are expected to result in
   additional storm development from the Permian Basin into
   south-central KS. Primary threat with these evening and overnight
   storms is large hail.

   ..Mosier.. 04/25/2021

[yoda]

[WhiteoutWX]

The slower/deeper progression has really evolved this towards more of a run of the mill type severe event in my opinion. The flow becomes more meridional which is not only causing much messier hodographs but is also leading to weaker lapse rates (hence the lack of instability on some of the models). The end result is likely to be messier storm modes. The “classic” dry line/tornadic supercell look the Euro was advertising from before really hasn’t been there for a few days now. The flooding threat may end up the bigger story out of this. 

[CheeselandSkies]

NAM isn't real impressive for Tuesday afternoon/evening. Has pretty much zero instability over the area where SPC has the threat outlined.

[Quincy]

The models (NAM/GFS/EC) show what I’d call “blotchy” instability maps. The wind profiles don’t look all that bad with guidance suggesting some backing/strengthening of low level winds. I think one of the issues is going to be ongoing/stratiform precipitation during the day, limiting instability. 

It could be a setup with a few widely spaced supercells, within an otherwise messy setup. Not sure where the best threat could evolve, but it could be anywhere from SW Texas (Fort Stockton area?) to western OK. Not sure I’m sold on much of a threat with northward extent into Kansas, but we’ll see. 

[Quincy]

Having had some more time to look over Tuesday’s setup, I have to say that most of it is a big mess. In my view, TX/OK looks a SLGT-risk caliber setup, but I wouldn’t even have enough confidence to include a sig hail area, due to limited/fragmented instability fields. 

Having said that, I’m more intrigued by prospects near the surface low/triple point in western Kansas. The NAM seems most aggressive, with 0-3km lapse rates around 9 C/km with favorable low-level moisture and substantial hodograph curvature. The EC/GFS show somewhat less favorable moisture return, leading to more marginal instability profiles. 

Since this is still 42-48 hours and the setup will continue to evolve, I don’t have high confidence in zeroing in on an area for severe thunderstorms. I’d lean toward surface low proximity, but that could fall into failure mode as well.

[Knightking2018]

  Keep on dreaming of that tornado outbreak. Of course as usual it turns into a major bust. 

[Radtechwxman]

Definitely disappointing to see a trough get sheared out and cutoff during peak season. Crazy how bad this has trended from days ago. Went from a strong negative tilt to a strung out positive tilt that cuts off an upper low. I really hope May can turn things around but I must say not liking the look of long range. Obviously that can and will change. Look how much Tues has changed. I'm starting to wonder if this will be another season of failed big setups with days that look marginal overperforming. I mean that's not bad as long as we get some nice tornadoes like the other day. 

[stormdragonwx]

Yeah its quite depressing, especially if you missed out on this past Friday.

 

[stormdragonwx]

Here's the current D2 outlook. Got a slight risk area with a 5 percent tornado. Storm chasing potential is trending more and more into the "meh" category for me. Might sit this one out but I'll have to look at the data closely tonight.

[CheeselandSkies]

11 minutes ago, stormdragonwx said:

Here's the current D2 outlook. Got a slight risk area with a 5 percent tornado. Storm chasing potential is trending more and more into the "meh" category for me. Might sit this one out but I'll have to look at the data closely tonight.

Like last Friday, should be a good day for the OK/TX-based chasers to get out and maybe (long shot) luck out with a storm like that Quanah/Lockett one. Not really worth traveling from outside the area, especially since it's looking like a one-and-done as opposed to a sequence of chase days (might be something somewhere Wednesday but details are looking very nebulous at this point).

[jojo762]

Going to go ahead and give the upslope flow a shot in NW KS/NE CO. Very much a boom or bust day... We'll see how it goes, but i'm cautiously optimistic for now.

Strong steam-wise vorticity combined with strong venting flow and low mid-level RH should at a minimum produce beautiful LP structures... Tornado threat is a bit more ambiguous, as is the case with most upslope flow setups. But easterly SFC flow combined with sufficient 3CAPE and do some spectacular things.

Biggest question appears to be moisture as guidance provides a variety of outcomes. If we verify on the higher-end of progs it could be a big'ish day, if we verify on the low end it could be slightly boring from a tornado perspective. 

[Chinook]

Finally, we are just a few hours away from this relatively weak severe weather event. Considering all things, there could have been a much better tornado day with this upper level trough, but it doesn't look like a big day today. Here are possible severe thunderstorm tracks from the HRRR today, includes maybe a little more activity than I might have expected for some of TX, OK.  (17z HRRR, up to 08z)

[stormdragonwx]

Yeah I chose to sit this one out. Was actually considering NW KS last night as well. Tomorrow doesn't look much better but I might look into it. Main thing keeping me at bay these two days is excessive cloud cover and messy storm modes.

[cstrunk]

Beautiful tornado warned supercell with very strong rotation just north of Guthrie, TX.

[CryHavoc]

21 minutes ago, cstrunk said:

Beautiful tornado warned supercell with very strong rotation just north of Guthrie, TX.

That cell is really cranking.