Severe Weather 5-6 through 5-9-24

[cheese007]

SPC has highlighted a swath of the plains from TX to NE for D6. May is in full swing!

 

Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0403 AM CDT Wed May 01 2024

   Valid 041200Z - 091200Z

   ...DISCUSSION...
   For Saturday/D4 to Sunday/D5, scattered to perhaps numerous
   thunderstorms are possible over a large section of the CONUS from
   the southern Plains into the Southeast. Mid 60s F to lower 70s F
   dewpoints will be common across the entire area, aided by southerly
   surface winds around an East Coast high. Aloft, generally weak flow
   will exist over the same areas, well east of a developing western
   upper trough. As such, the weak shear will likely minimize overall
   severe potential through Sunday/D5.

   For Monday/D6, models have shown increased run-to-run consistency in
   depicting a deep upper trough developing over the Great Basin and
   emerging into the Plains. Rich low-level moisture will be in place
   ahead of this system, which is forecast to enter the central Plains
   with a negative tilt and strong shear. While minor trough-geometry
   differences exist amongst the models, the combination of
   strengthening shear, a potentially deep surface low and ample
   moisture and instability necessitate introducing severe
   probabilities for parts of the Plains on Monday. All facets of
   severe appear possible with such a system, including supercells,
   squall lines, tornadoes, damaging winds and large hail.

   ..Jewell.. 05/01/2024

[WxSynopsisDavid]

31 minutes ago, cheese007 said:

SPC has highlighted a swath of the plains from TX to NE for D6. May is in full swing!

 

Day 4-8 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0403 AM CDT Wed May 01 2024

   Valid 041200Z - 091200Z

   ...DISCUSSION...
   For Saturday/D4 to Sunday/D5, scattered to perhaps numerous
   thunderstorms are possible over a large section of the CONUS from
   the southern Plains into the Southeast. Mid 60s F to lower 70s F
   dewpoints will be common across the entire area, aided by southerly
   surface winds around an East Coast high. Aloft, generally weak flow
   will exist over the same areas, well east of a developing western
   upper trough. As such, the weak shear will likely minimize overall
   severe potential through Sunday/D5.

   For Monday/D6, models have shown increased run-to-run consistency in
   depicting a deep upper trough developing over the Great Basin and
   emerging into the Plains. Rich low-level moisture will be in place
   ahead of this system, which is forecast to enter the central Plains
   with a negative tilt and strong shear. While minor trough-geometry
   differences exist amongst the models, the combination of
   strengthening shear, a potentially deep surface low and ample
   moisture and instability necessitate introducing severe
   probabilities for parts of the Plains on Monday. All facets of
   severe appear possible with such a system, including supercells,
   squall lines, tornadoes, damaging winds and large hail.

   ..Jewell.. 05/01/2024

Shouldn’t the thread headline read “5-6-24” instead of “4-6-24”?

[cheese007]

1 hour ago, WxSynopsisDavid said:

Shouldn’t the thread headline read “5-6-24” instead of “4-6-24”?

What do you mean it's totally correct

[cstrunk]

Maybe I need to convince my boss to let me take my birthday off from work...

[andyhb]

12z guidance looks overall pretty dangerous on Monday, especially in KS. Some big time dates popping up in both the Great Plains and Southern Plains sectors of the 12z CIPS analogs. Biggest questions are again going to be related to trough timing (how much does it slow down) and amplitude.

[cheese007]

Gonna be a busy week next week

 

Day 4-8 Convective Outlook  

   NWS Storm Prediction Center Norman OK

   0400 AM CDT Fri May 03 2024

 

   Valid 061200Z - 111200Z

 

   ...SEVERE WEATHER OUTBREAK POSSIBLE ON D4/MON...

 

   ...DISCUSSION...

   A multi-day period of organized severe thunderstorm potential

   appears likely across parts of the central to eastern CONUS next

   week, beginning on Day 4/Monday across the Plains, and continuing

   through at least Day 6/Wednesday.

 

   ...Day 4/Monday...

   A negatively tilted upper trough will eject northeastward over the

   northern/central Plains on Monday. Pronounced low-level mass

   response will encourage rich low-level moisture to advect northward

   over the southern/central Plains, as a surface low rapidly deepens

   over the northern High Plains. Strong deep-layer shear and at least

   moderate instability are expected to be in place ahead of a surface

   dryline extending across the southern/central Plains.

 

   Thunderstorms will likely erupt along the length of the dryline by

   late Monday afternoon from southern NE into central KS and

   north-central OK. Supercells are likely to be the dominant mode

   initially given the strength of the deep-layer shear. Both very

   large hail and tornadoes will be possible with these supercells as

   they spread eastward across the southern/central Plains through

   Monday evening. With a southerly low-level jet forecast to

   strengthen to at least 50-60 kt Saturday evening, a corresponding

   rapid increase in low-level shear will likely support a continued

   threat for tornadoes with any discrete convection. Some of these

   tornadoes could be strong. The severe threat will likely continue

   Monday night with eastward extent across the Plains, before

   convection possibly weakens some towards early Tuesday morning.

   Given increased confidence in high-end severe potential, a 30%

   severe area has been introduced from parts of southern NE into

   central KS and north-central OK.

 

   ...Day 5/Tuesday...

   The large-scale upper trough/low is forecast to gradually occlude

   over the northern Plains on Tuesday. But, an enhanced mid-level jet

   and embedded vorticity maximum will likely overspread parts of the

   Upper Midwest, mid MS Valley, and OH Valley through Tuesday evening.

   An expansive warm sector will likely be in place across these

   regions ahead of a surface cold front/dryline. Robust convection

   should develop along/ahead of these boundaries through the day.

   Sufficient instability and deep-layer shear will likely exist to

   support organized severe thunderstorms, including supercells posing

   a threat for all severe hazards. The northeastward extent of the

   warm sector remains somewhat uncertain into the OH Valley. Still,

   some severe risk will probably persist into Tuesday evening/night

   with eastward extent across the mid MS Valley and lower OH

   Valley/Midwest. Expansion of the 15% severe area may be needed in

   later outlooks, pending better model agreement and increased

   confidence in the eastward extent of rich low-level moisture and

   related instability.

 

   ...Day 6/Wednesday...

   The upper trough/low should gradually evolve eastward across the

   northern Plains on Wednesday. While there are still some differences

   in model guidance regarding the evolution of an embedded shortwave

   trough, there appears to be enough agreement in the synoptic pattern

   to include a 15% severe delineation for Wednesday for parts of the

   southern Plains into the ArkLaTex/Ozarks and towards the mid MS

   Valley. Across these areas, strong instability is forecast to

   develop east of a front/dryline. With enhanced mid-level flow

   persisting with a westerly mid/upper-level jet, organized severe

   thunderstorms should once again develop Wednesday afternoon.

   Supercells posing a threat for all severe hazards may occur. The

   northern/eastern extent of the severe threat is unclear, as the

   convection from Tuesday may tend to limit better low-level moisture

   return into the OH/TN Valleys. Depending on model trends over the

   next few days, the 15% severe area may need to be expanded to

   include these regions.

 

   ...Day 7/Thursday and Day 8/Friday...

   Some severe threat may continue on Thursday from parts of TX into

   the lower MS Valley/Southeast, generally along/south of a front and

   any convection that develops Wednesday. Too much uncertainty

   currently exists to include a 15% severe area at this time, but

   trends will be monitored. A severe risk also appears possible next

   Friday across the same general regions, but confidence in the

   placement of the front and convection is even lower than Thursday.

 

   ..Gleason.. 05/03/2024

 

[cheese007]

P strong wording on the D3 and D4-8 outlooks. Already talking about upgrades to the former

SPC AC 040729

 

   Day 3 Convective Outlook  

   NWS Storm Prediction Center Norman OK

   0229 AM CDT Sat May 04 2024

 

   Valid 061200Z - 071200Z

 

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF

   THE SOUTHERN/CENTRAL PLAINS...

 

   ...SUMMARY...

   Numerous severe thunderstorms will likely develop and move eastward

   Monday afternoon and evening across parts of the southern/central

   Plains. Strong tornadoes, very large to giant hail, and damaging

   winds all appear possible.

 

   ...Synopsis...

   A negatively tilted upper trough with embedded 50-70 kt mid-level

   speed maximum will eject northeastward across the northern/central

   Plains on Monday. At the surface, the primary low should consolidate

   over the northern High Plains of eastern MT/western ND and vicinity,

   with a secondary surface low possibly developing over the central

   High Plains by Monday evening. A rather moist low-level airmass,

   with surface dewpoints generally in the mid 60s to low 70s, will

   spread northward across the southern/central Plains ahead of an

   eastward-mixing dryline. A warm front should eventually extend

   eastward across parts of NE/IA, and this boundary will probably be

   the northern limit of appreciable severe-thunderstorm potential.

 

   ...Southern/Central Plains...

   A severe-weather outbreak still appears possible across parts of the

   southern/central Plains on Monday, focused from south-central/

   southeast NE into central/eastern KS and much of OK. Robust diurnal

   heating of the moist low-level airmass, coupled with steep mid-level

   lapse rates overspreading much of the warm sector, will likely

   foster moderate to strong instability (MLCAPE generally ranging from

   2000-3500 J/kg) by Monday afternoon. Enhanced mid-level winds and a

   favorably veering/strengthening wind profile with height through

   mid/upper levels will support around 40-55 kt of effective bulk

   shear, stronger with northward extent in KS/NE.

 

   Current expectations are for scattered supercells to erupt along the

   length of the dryline in south-central NE and western/central KS by

   mid to late Monday afternoon, coincident with stronger large-scale

   ascent overspreading this region. Given the rather favorable

   thermodynamic and kinematic parameter space, very large to giant

   hail (2-4 inch diameter) will likely be a threat with these initial

   supercells. The threat for tornadoes should quickly increase through

   the late afternoon and early evening in tandem with a strengthening

   southerly low-level jet. Ample 0-1 km and effective SRH shown in

   various NAM/GFS forecast soundings suggest a threat for strong

   tornadoes with any supercell that can remain discrete. With time

   Monday evening and into early Tuesday morning, upscale growth into

   multiple linear structures is probable, with an increased threat for

   severe/damaging winds, along with embedded tornadoes given the

   forecast strength of the low-level shear.

 

   The southward extent of the substantial severe risk into OK and

   north TX remains somewhat uncertain, as better forcing for ascent

   will tend to remain across the central Plains. Still, modest

   mid-level height falls should encourage isolated to perhaps widely

   scatted supercells developing along the length of the dryline into

   the southern Plains. Very large hail and strong tornadoes will be

   the main threats with any supercell that can develop and persist

   across this region Monday afternoon/evening. Model trends will also

   be monitored for a more favorable corridor of strong tornadoes and

   giant hail, which may necessitate greater severe probabilities for

   Monday in a later outlook.

 

   ..Gleason.. 05/04/2024

 

ZCZC SPCSWOD48 ALL

   ACUS48 KWNS 040900

   SPC AC 040900

 

   Day 4-8 Convective Outlook  

   NWS Storm Prediction Center Norman OK

   0400 AM CDT Sat May 04 2024

 

   Valid 071200Z - 121200Z

 

   ...DISCUSSION...

   An active period of organized severe thunderstorms should persist

   into at least the middle of next week across parts of the southern

   Plains into the mid MS Valley, Mid-South, and Midwest/OH Valley. The

   15% severe areas for both Day 4/Tuesday and Day 5/Wednesday have

   been expanded based on latest model trends.

 

   ...Day 4/Tuesday...

   The primary upper low over the northern Plains is forecast to

   gradually occlude on Tuesday. But, a strong mid-level jet streak

   should overspread parts of the mid MS Valley and Midwest through the

   day. A secondary surface low should develop northeastward across

   these regions, with a warm front also lifting northward towards

   southern WI and southern Lower MI. Thunderstorms related to

   low-level warm advection and activity that has spread eastward from

   the southern/central Plains may be ongoing Tuesday morning. It

   remains unclear if these thunderstorms will strengthen once again as

   they develop eastward in tandem with a destabilizing warm sector.

   Additional robust convection will likely develop Tuesday afternoon

   farther south along the dryline over the Ozarks and Mid-South. A

   favorable parameter space for supercells and all severe hazards

   remains evident, with the threat for severe thunderstorms continuing

   Tuesday afternoon/evening across parts of the OH Valley.

 

   ...Day 5/Wednesday...

   Although some differences in model guidance regarding the upper-air

   pattern across the central/eastern CONUS begin to emerge by

   Wednesday, there is still good agreement that a belt of strong

   mid-level flow will remain in place from the southern/central Plains

   northeastward to the OH Valley and Great Lakes. It appears that

   another embedded shortwave trough will advance eastward from the

   southern/central Plains into the mid MS Valley by Wednesday evening.

   A very moist and moderately to strongly unstable airmass should

   reside to the east of a cold front/dryline across these regions,

   potentially extending as far north into much of the Midwest/OH

   Valley. Strong deep-layer shear will favor organized convection,

   including supercells and bowing line segments posing a threat for

   all severe hazards. Depending on the influence of prior convection,

   the very favorable parameter space forecast for Wednesday across

   parts of the southern Plains into the mid MS Valley and OH Valley

   may necessitate greater severe probabilities in a later outlook.

 

   ...Day 6/Thursday...

   Multiple days of robust and potentially widespread convection

   complicates the severe potential for Thursday. Still, some severe

   risk remains evident along/south of what will probably be a

   convectively reinforced front/boundary extending across parts of the

   southern Plains into the Southeast and Mid-Atlantic. It is possible

   that one or more 15% severe areas for Thursday will be needed for

   these regions given favorable forecast instability/shear. But, this

   is still dependent on better agreement in model guidance regarding

   the extent/placement of moderate to strong instability, and overall

   convective coverage Thursday afternoon/evening.

 

   ...Day 7/Friday and Day 8/Saturday...

   The spatial extent of the warm sector should tend to become more

   confined late next week and into the weekend. There is a fair amount

   of spread in model guidance regarding the strength and placement of

   an upper trough/low over the eastern CONUS in this time frame.

   Still, a severe risk may continue Friday along/south of a front that

   should be in place over parts of the Southeast. Any lingering severe

   threat into Saturday may be even farther south and confined to

   mainly parts of FL.

 

   ..Gleason.. 05/04/2024

[Chinook]

I think parameters will be very high for tornadoes on Monday night. The models show a small cap in place. Lifting condensation levels should be quite low in Oklahoma with higher dew points. As usual, the ramp-up in lower level winds will occur at night to possibly increase chances of tornadoes.

[Quincy]

The synoptic look is there. Broad troughing across the central US and a steady conveyor belt of enhanced upper level flow ejecting toward the Plains/Midwest. 

The NAM/GFS show plentiful moisture with upper 60s/lower 70s dews on Monday through the ENH risk area. The Euro is tempered a bit, but still favorable for severe.

Tuesday could be a volatile day from the Ozarks to the Midwest, assuming there isn’t significant convective overturning early in the day. A robust jet streak is progged to be aiming right at MO/IL with lower 70s dew points and a supercell wind profile from AR/MO into IL and vicinity.

There is still time for the forecast to trend and evolve, but it’s looking like another multi day event is on tap. 

[Ed, snow and hurricane fan]

I hadn't read the ICT discussion but this showed up on X

 

 

[thunderbird12]

The NAM/GFS might be a little too aggressive with moisture return on Monday, with potentially lots of convection and related outflow across Texas the rest of tonight into tomorrow. However, even if the moisture isn't quite as pristine as the NAM/GFS would suggest, Monday still looks like a big severe day. Seems like there has been a trend (especially in the 00Z NAM) for a somewhat stronger secondary shortwave and jet max approaching Oklahoma near and after 00Z Monday evening. That would be an ominous scenario if it verifies.  

 

[stormdragonwx]

Fine, I'll be the weather weenie for once and say it goes high risk on Mon morning. lol

[cheese007]

D2 Mod with a 15% hatched tor risk

Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0100 AM CDT Sun May 05 2024

   Valid 061200Z - 071200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   WESTERN/CENTRAL OKLAHOMA AND SOUTH-CENTRAL KANSAS...

   ...SUMMARY...
   Numerous severe thunderstorms are expected to develop and move
   eastward Monday afternoon through Monday night across parts of the
   southern/central Plains. Multiple strong/potentially long-track
   tornadoes, very large to giant hail, and severe/damaging winds all
   appear likely.

   ...Synopsis...
   A negatively tilted upper trough with embedded 50-70 kt mid-level
   speed maximum will eject northeastward across the northern/central
   Plains on Monday. At the surface, the primary low will consolidate
   over the northern High Plains of eastern MT into western ND/SD and
   vicinity, with a secondary surface low forecast to develop over the
   central High Plains by Monday evening. A rather moist low-level
   airmass, with surface dewpoints generally in the mid 60s to low 70s,
   will spread northward across the southern/central Plains ahead of an
   eastward-mixing dryline and southeastward-moving cold front. A warm
   front should eventually reach eastward across parts of NE/IA. This
   warm front should be the northern limit of appreciable
   severe-thunderstorm potential through Monday night.

   ...Southern/Central Plains...
   Confidence has increased in a corridor of greater potential for
   strong tornadoes and very large hail, with multiple supercells
   likely to develop across south-central KS and western/central OK
   late Monday afternoon and continuing through much of the evening.
   Accordingly, a Moderate Risk has been introduced for this area.

   Daytime heating of the moist low-level airmass, coupled with steep
   mid-level lapse rates, will foster moderate to strong instability
   developing along/east of the dryline Monday afternoon. Peak
   pre-convective MLCAPE will likely reach 2500-4000 J/kg across much
   of central KS into western/central OK and northwest TX. Strong
   deep-layer shear of 40-50 kt will easily support supercells with
   initial thunderstorm development. Convective initiation appears
   likely by early Monday afternoon as ascent with the lead shortwave
   trough overspreads NE/KS. Very large hail will be a threat
   initially, but most guidance suggests a fairly quick transition to a
   more linear mode with time Monday afternoon/evening, especially as
   the cold front overtakes the dryline. An increasing threat for
   damaging winds and embedded tornadic circulations will likely occur
   as this mode transition occurs, in tandem with strengthening
   boundary-layer shear associated with a strengthening southerly
   low-level jet. This damaging-wind/tornado threat may continue into
   the overnight hours into parts of IA/MO, and the Slight Risk has
   been expanded eastward to account for this potential.

   Farther south across western OK and south-central KS, more modest
   large-scale ascent and related mid-level height falls associated
   with a more westerly mid/upper-level jet will eventually overspread
   the dryline and warm sector by late Monday afternoon. Although
   overall convective coverage will likely be lower compared to
   locations farther north, there should be a better chance for
   supercell structures to be maintained, as deep-layer shear vectors
   appear more orthogonal to the initiating boundary (dryline). A
   southerly low-level jet should strengthen to around 40-45 kt through
   early Monday evening across this area, greatly enhancing
   corresponding low-level shear and effective SRH. The best chance for
   strong, potentially long-track tornadoes and giant hail (3-4 inches)
   should exist with any supercells that can persist Monday evening in
   a very favorable thermodynamic and kinematic parameter space.
   Similar to locations farther north in KS/NE, upscale growth should
   eventually occur across central/eastern OK. A threat for damaging
   winds and tornadoes (some potentially strong) should continue Monday
   night into early Tuesday with eastward extent across the southern
   Plains given a sufficiently unstable and strongly sheared
   environment.

   ..Gleason.. 05/05/2024

 

[Quincy]

Models are trending faster with the lead shortwave ejecting across Kansas/Nebraska. In fact, guidance suggests that large scale forcing may reach western Kansas by 15-18z with early convective initiation.

This solution causes a cold front to rapidly overtake the dryline. The result favors a linear storm mode across Kansas and possibly even into northern Oklahoma. 

Farther south is a different story. If you look at the 6z 3km NAM, notice how another belt of enhanced upper level flow stretches from New Mexico into West Texas. This flow is more westerly as opposed to southwesterly up north. The forcing across the southern High Plains/western Oklahoma area is later than up north, arriving closer to 21-00z. Forecast soundings across central Oklahoma in this time frame show residual capping as somewhat warmer mid-level temperatures are noted. 

This solution would delay convective initiation until late afternoon. With that said, forcing timed more favorably with peak heating, along with a westerly component to the upper level winds, suggests a more discrete storm mode. 

To quickly recap, the trend favors quick shortwave ejection across the Central Plains with a more linear storm mode there. There’s a split emerging in the flow across the southern High Plains, favoring a secondary, more discrete supercell thunderstorm risk over the Southern Plains.

In my mind, the question is, does this trend continue? If not, the snapshot in time favors an ominous risk across southwestern into south-central Oklahoma and far northern Texas from late afternoon into the evening. It places Oklahoma City on the fringe of the greatest threat and the timing would likely fall just after sunset. Linear storm modes are favored to the north, while at least isolated supercell development is probable to the southwest/south. 

If the trend continues, you could see the primary threat area get booted down toward the Red River and northwest Texas. That would be better for Oklahoma, especially OKC metro. 

I’ll be watching trends closely today. I’m not a fan of the current progs, as they place a significant severe threat close to Oklahoma City, after dark. There’s not a ton of time left, so the next few model runs will be critical. 

[Chinook]

5 hours ago, Quincy said:

Models are trending faster with the lead shortwave ejecting across Kansas/Nebraska. In fact, guidance suggests that large scale forcing may reach western Kansas by 15-18z with early convective initiation.

This solution causes a cold front to rapidly overtake the dryline. The result favors a linear storm mode across Kansas and possibly even into northern Oklahoma. 

Farther south is a different story. If you look at the 6z 3km NAM, notice how another belt of enhanced upper level flow stretches from New Mexico into West Texas. This flow is more westerly as opposed to southwesterly up north. The forcing across the southern High Plains/western Oklahoma area is later than up north, arriving closer to 21-00z. Forecast soundings across central Oklahoma in this time frame show residual capping as somewhat warmer mid-level temperatures are noted. 

This solution would delay convective initiation until late afternoon. With that said, forcing timed more favorably with peak heating, along with a westerly component to the upper level winds, suggests a more discrete storm mode. 

To quickly recap, the trend favors quick shortwave ejection across the Central Plains with a more linear storm mode there. There’s a split emerging in the flow across the southern High Plains, favoring a secondary, more discrete supercell thunderstorm risk over the Southern Plains.

In my mind, the question is, does this trend continue? If not, the snapshot in time favors an ominous risk across southwestern into south-central Oklahoma and far northern Texas from late afternoon into the evening. It places Oklahoma City on the fringe of the greatest threat and the timing would likely fall just after sunset. Linear storm modes are favored to the north, while at least isolated supercell development is probable to the southwest/south. 

If the trend continues, you could see the primary threat area get booted down toward the Red River and northwest Texas. That would be better for Oklahoma, especially OKC metro. 

I’ll be watching trends closely today. I’m not a fan of the current progs, as they place a significant severe threat close to Oklahoma City, after dark. There’s not a ton of time left, so the next few model runs will be critical. 

oh you mean linear like this? I guess this raises the chances for severe winds

 

[Wmsptwx]

Boooo linear sucks

[southmdwatcher]

There will be some semi-discrete and discrete storms in southern Kansas and Oklahoma. Just a matter of how many.

[andyhb]

1 hour ago, Wmsptwx said:

Boooo linear sucks

Great contribution.

I don't know if you want to see the results of a non-linear solution in the parameter space being suggested here.

[Quincy]

I’ve had some time to review the 00z data and it’s not making me feel any more comfortable. The “trend” I eluded to earlier has stopped and we seem to be zeroing in with confidence on the probable outcome on Monday. 

CAMs continue to show a quick-to-linear evolution of convection across Kansas, but virtually every CAM shows at least isolated supercell development between I-40 and the KS/OK border area by late afternoon. 

Another observation is that multiple models show or at least hint at prefrontal convection as well, somewhere near or east of I-35 during the early evening hours. 

At this point, I’m grasping at straws to try to find some limiting factors…

1. The 3km NAM does show marginal low-level lapse rates ahead of approaching convection from OKC and points south. (Around 6 C/km) The bad news? Every other model, including the NSSL WRF, shows considerably steeper lapse rates. It may be related to a low level moist bias. 

2. The NAM/WRF suite shows clustered storm modes, trending toward bowing structures around OKC. The problem? The wind profiles are much more supercellular in nature, so I’d take reflectivity progs with a grain of salt.

Another peculiar note is that the usually convective happy FV3 shows very little CI across Oklahoma, in an otherwise extremely favorable environment. Perhaps it’s residual mid-level capping, which appears minimal at best by 00z. 

Almost any way you slice it, the setup has an awfully high ceiling across Oklahoma and vicinity. 

Even in the best case, where you have a bowing structure surging SE across the state, the expected wind profiles and strong/extreme instability favor embedded tornadoes.

If convection remains isolated across Oklahoma, even with only a couple of cells, the risk of any of those cells producing significant, potentially long-lived severe is rather high. 

Then you have the worst case scenario, which is presented by some models, including the 00z HRRR: a broken band of supercells ahead of the dryline with pre “frontal” cells, all of which seem to mature around or after sunset, over or close to Oklahoma City. 

Reference the latest SREF convective probabilities, at 03z Tue (within the most favorable environment) and there are >40% probabilities of convection near and south of I-40, despite models showing a relative lack of CI in the area. (Convective precip > 0.01” with >2000 J/kg CAPE and > 30kts effective shear)

[MidwestChaser]

Day 1 still a Moderate but:

THIS IS A HIGH-END ENVIRONMENT. AN UPGRADE TO A TORNADO-DRIVEN HIGH  
RISK WAS CONSIDERED. THERE REMAINS SOME LINGERING UNCERTAINTY WITH  
REGARD TO THE NUMBER OF INTENSE TORNADOES THAT WILL OCCUR. AN  
INCREASE IN TORNADO PROBABILITIES WILL CERTAINLY BE WARRANTED SHOULD  
CONFIDENCE IN COVERAGE AND PREFERRED CORRIDORS INCREASE.

[stormdragonwx]

Might be a little gun shy after the 5/20/19 debacle. Totally understandable. Bet it gets reconsidered at 1630z

[gopack42]

If I may.....would y'all mind suggesting some good people to follow on X/Twitter to keep track of severe forecasting and discussion?  Thank you very much!

[ICEHOCEY77]

going to be nasty, storms only going to intensify after dark. Kind of a worst nightmare from a chaser perspective too. 

[Quincy]

3 hours ago, stormdragonwx said:

Might be a little gun shy after the 5/20/19 debacle. Totally understandable. Bet it gets reconsidered at 1630z

I don’t think they’re not making the decision to upgrade based on something like that. I distinctly remember that there were some caveats with that event in hindsight, most notably the poor low level lapse rates. Monday evening’s forecast environment is high end. Not the high end that we talk about once or twice a season, but more like the highest end we’ve seen in years around here.

The 06z HRRR is about as ugly as a model run as I’ve ever seen for Oklahoma and I’m literally having trouble sleeping. 5/20/19 had the “swarm” of small supercells on the HRRR, but this is apples and oranges. The HRRR shows isolated, beastly supercells, no surprise given the background environment.

I mentioned earlier that I’m having trouble seeing limiting factors in the environment. Only one model shows weaker low level lapse rates (3km NAM), but even that has seemed to have backed off. 

Analogs should be used with a grain of salt, but the synoptic similarities to 4/26/91 are legitimate.

Two things are going to be key in determining MDT vs. HIGH risk tornado forecast/verification:

1. Where is the corridor of greatest tornado potential? HRRR favors the northern half of Oklahoma, while NAM/WRF models focus in on central to southern Oklahoma. 

It’s not a matter of if there’s a tornado outbreak, but where the outbreak occurs. Model biases are highlighting the south vs. north divide in the coverage of storms.

2. How many storms (discrete, long lived) are there? Given the background environment and WNW mean upper level flow atop a robust 50+ knot southerly low level jet, it’s a textbook supercell wind profile. Add in the subtle capping, timing of the wave, low level moisture and thermodynamic profiles and pattern recognition screams “tornado outbreak.”

If you only have isolated convective development across Oklahoma, you can envision a scenario with a couple of long track tornadic supercells, much like a 4/26/91 type event.

I pulled the 00z 4/27/91 OUN sounding and noted some warming around 700-600mb that probably contributed to the lack of sustained supercells with southward extent, effectively sparing the OKC metro area. 

With tonight’s event, I think just about every model at this point suggests you will get CI down to I-40… but, are the NAM/ARW solutions correct with more numerous CI, all the way down toward the Red River?

I mentioned earlier about the NAM showing more of a clustered storm mode, but meteorology warns against that. (Upper level flow just about perpendicular to dryline, residual capping through mid/late afternoon, timing of the wave, etc.) 

With that said, the HRRR seems to be the outlier now with a dearth of CI across southern Oklahoma. Although the FV3 curiously also showed a lack of CI the south, which is both worrisome and a bit peculiar given the tendency for the model to over-convect. 

When you have a bonafide extreme environment and models only show sparse convective development, that’s an ominous warning sign that any storms that due form have a high likelihood to be strong/intense. At that point, you have to use meteorology and understand that the background environment is favorable over a broad area (much of Oklahoma).

Going back to storm coverage, the NAM/WRF models show more storm coverage, including all the way down to the Red River with the 12km and 3km NAM.

In my experience, given respective model biases, a compromise between the NAM and HRRR is going to get you a reasonable idea of what to expect.

If you take the 06z HRRR solution of discrete storm modes and blend it with the NAM, which shows more convective coverage, including with southward extent, you probably have a high-risk caliber tornado outbreak over at least a portion of Oklahoma.

Again, is the area of focus zeroed in on northern Oklahoma, like 4/26/91, or do we realize an outbreak that extends into and south of OKC, possibly down to near the Red River?

That’s your difference between moderate and high risk. You’re not going to see the SPC go high risk for an 18-24 hour lead time for 2-3 tornadic supercells. If they’re a broader corridor that can sustain multiple such storms and if seems like we may be trending toward that, then you can see an upgrade to high risk.

From a public awareness perspective, MDT vs. HIGH is almost irrelevant. It only takes one storm to change communities and lives. High risk is not something you should hope for, much like hoping/wishing for EF-5 tornadoes/damage.

I’ve lived in Oklahoma since 2016 and I think this is the worst I’ve felt about a forecast in that time frame. 

I don’t know what else to say at this point. I can’t see much changing. We just need to nail down the coverage of storms and go from there. Hopefully the more intense storms take a track that causes the least amount of damage/destruction.

18 minutes ago, ICEHOCEY77 said:

going to be nasty, storms only going to intensify after dark. Kind of a worst nightmare from a chaser perspective too. 

This is ugly as well. Nighttime storms, long tracking, potentially near at least one metro area (OKC) and possibly multiple (Tulsa, maybe even Wichita?). Chaser convergence is already bad enough with any hyped up event in Oklahoma. 

Sure, at least we don’t expect the tornado threat to target OKC at rush hour, but it’s not like after dark is much better. I hope people, including chasers, take warnings seriously and that everyone stays safe and prepared. 

[yoda]

High risk coming on 1300z SPC OTLK 

 

 

   Mesoscale Discussion 0646
   NWS Storm Prediction Center Norman OK
   0712 AM CDT Mon May 06 2024

   Areas affected...Central...West-central and North-central Oklahoma
   Into Far Southern Kansas

   Concerning...Outlook upgrade 

   Valid 061212Z - 061315Z

   SUMMARY...An upgrade to High Risk will be done for the upcoming 13Z
   Day 1 Outlook. The following areas will be upgraded to High Risk.

   DISCUSSION...Central Oklahoma
   North-central Oklahoma
   West-central Oklahoma
   Far Southern Kansas

   Please refer to 13Z Day 1 Outlook for detailed reasoning.

   ..Broyles/Edwards.. 05/06/2024

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...TSA...ICT...OUN...DDC...

[Powerball]

13 minutes ago, yoda said:

High risk coming on 1300z SPC OTLK 

 

 

   Mesoscale Discussion 0646
   NWS Storm Prediction Center Norman OK
   0712 AM CDT Mon May 06 2024

   Areas affected...Central...West-central and North-central Oklahoma
   Into Far Southern Kansas

   Concerning...Outlook upgrade 

   Valid 061212Z - 061315Z

   SUMMARY...An upgrade to High Risk will be done for the upcoming 13Z
   Day 1 Outlook. The following areas will be upgraded to High Risk.

   DISCUSSION...Central Oklahoma
   North-central Oklahoma
   West-central Oklahoma
   Far Southern Kansas

   Please refer to 13Z Day 1 Outlook for detailed reasoning.

   ..Broyles/Edwards.. 05/06/2024

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...TSA...ICT...OUN...DDC...

Caveat Emptor: It appears to be (in part) a Broyles production...

[yoda]

3 minutes ago, Powerball said:

Caveat Emptor: It appears to be (in part) a Broyles production...

Wendt/Darrow did the 0600Z SPC OTLK and specifically mentioned that an upgrade was possible... and they deferred due to some lingering uncertainty... so...

[Quincy]

Broyles, but with Edwards.

This morning it looks like the HRRR is slowly nudging a bit to the NW, which could be good for OKC. With that said, it also hints at a confluence band of storms attempting to fire by mid-afternoon, just west of the I-44 to I-35 corridor.

Forecast soundings show minimal convective inhibition by 19-20z over central Oklahoma, so that’s plausible. The main action will probably initiate west of there near the dryline.

It seems like there’s always a curveball or two, but we’ll see. I still think the northwest to north-central Oklahoma area is in ground zero, pretty much no matter what happens. It’s a little more conditional near and south of Oklahoma City. 

Hopefully the 12z suite gets into more agreement with details. 

[stormdragonwx]

My target area was Enid so this lines up with what I suspected unfortunately

[yoda]