April 23-May 5, 2024 | Multi-Day Severe Weather/Tornado Outbreak

[snowlover2]

Day 1 disco is downright scary.

Quote

Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0104 AM CDT Sat Apr 27 2024

   Valid 271200Z - 281200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   NORTH TEXAS...OKLAHOMA...SOUTHEAST KANSAS AND FAR SOUTHWEST
   MISSOURI...

   ...SUMMARY...
   Numerous severe thunderstorms are likely today and tonight across
   the southern and central Plains into the lower to mid Missouri
   Valley. The greatest potential for severe storms will be from north
   Texas into Oklahoma and southeast Kansas, where strong tornadoes,
   very large hail over 2 inches in diameter and widespread damaging
   winds (some over 70 mph), are expected to occur. A broader area of
   severe threat will extend from south-central Texas
   north-northeastward to the Great Lakes.

   ...Tornado Outbreak Expected Today From North Texas into
   Oklahoma...Southeast Kansas and Far Southwest Missouri...

   ...Southern Plains...
   An upper-level trough will move through the Desert Southwest today
   as an 80 to 90 knot mid-level jet translates quickly eastward
   through the base of the system. Ahead of the trough, a moist and
   unstable airmass will be in place across much of the southern and
   central Plains. At the surface, a low will move eastward across
   southwest Kansas with a dryline extending southward through far
   western Oklahoma and west Texas. Surface dewpoints to the east of
   the dryline will be in the mid to upper 60s F. In response to warm
   advection this morning, a cluster of thunderstorms is expected to
   develop to the east of the dryline across northwest Texas. This
   cluster is forecast to spread north-northeastward into western
   Oklahoma by late morning. Large hail and wind damage will be likely
   with the stronger cells within this cluster. An outflow boundary
   with this convection should setup across west-central Oklahoma by
   early afternoon, with a moist and unstable airmass extending
   eastward from the boundary across much of central and eastern
   Oklahoma northward into southeast Kansas. This undisturbed airmass
   is expected to be favored for the greatest severe threat this
   afternoon and evening.

   The mid-level jet is forecast to eject quickly northeastward across
   the southern Plains this afternoon. This will result in strong
   deep-layer shear across most of the southern Plains, and will create
   a large-scale mass response that will be very favorable for severe
   storms, including supercells and bowing line segments. As the core
   of the mid-level jet moves into the southern Plains during the mid
   to late afternoon, a 50 to 60 knot low-level jet will rapidly
   strengthen. RAP forecast sounding along and near the low-level jet
   during the late afternoon look very favorable for tornadoes, with
   backed surface flow, and long looping hodographs. As the low-level
   jet strengthens, 0-3 km storm-relative helicity is forecast to
   increase to around 400 m2/s2 across much of central and eastern
   Oklahoma into southeast Missouri. The more dominant and supercells
   that interact with the western and northern edge of the low-level
   jet are expected to become tornadic. Several strong tornadoes will
   be likely, and a few long-track EF3+ tornadoes will be possible.

   In addition to the tornado threat, forecast soundings have 700-500
   mb lapse rates near 8 C/km across much of the warm sector this
   afternoon from north Texas to southeast Kansas. This will be
   favorable for very large hail, with hailstones over 2 inches in
   diameter likely with the more intense storms. Later in the evening,
   a line of severe storms is expected to form, moving eastward across
   eastern Oklahoma and north Texas. Wind gusts over 70 mph will be
   possible with the more intense parts of the line. QLCS tornadoes
   will also be possible with rotating cells embedded in the line late
   this evening into the overnight period.

   ...Central Plains/Lower to Mid Missouri Valley...
   An upper-level low will move through the southern Rockies today, as
   the exit region of a mid-level jet overspreads the central Plains.
   At the surface, a warm front will be located from near a surface low
   in southwest Kansas east-northeastward into the mid Missouri Valley.
   This front will be a focus for convective development this
   afternoon. A band of severe storms is expected to form near the
   front and move northward across northern Kansas into southern
   Nebraska during the early to mid afternoon. RAP forecast soundings
   in northeast Kansas near the front from 18Z to 21Z have MLCAPE near
   3000 J/kg, 0-6 km shear around 60 knots, and steep low to mid-level
   lapse rates. This environment will be very favorable for supercells
   with large hail. Hailstones greater than 2 inches in diameter will
   be possible with the more intense storms. In addition, forecast
   soundings have 0-3 km storm-relative helicity in the 250 to 300
   m2/s2 range, suggesting that tornadoes will be likely with the more
   discrete supercells. A few strong tornadoes will be possible.

   Further west into northwest Kansas and eastern Colorado, cold
   temperatures aloft, strong large-scale ascent associated with an
   upper-level low, and strong deep-layer shear will likely support
   lower-topped supercells with large hail and strong wind gusts this
   afternoon.

   ...Mid to Upper Mississippi Valley/Great Lakes...
   An upper-level trough will move northeastward across the Great Lakes
   region today. From near the trough, and southwestward into the mid
   to upper Mississippi Valley, a wide corridor of moderate instability
   will be in place by afternoon. A warm front will be in located along
   the northern edge of the instability, from Iowa northeastward into
   south-central Wisconsin and north-central lower Michigan. As surface
   heating takes place and low-level convergence increases along the
   front, thunderstorms will likely form in the vicinity of the
   boundary. Forecast soundings near the front at 21Z have MLCAPE
   around 3000 J/kg, along with 40 knots of deep-layer shear. This
   should support supercells with potential for large hail and wind
   damage. The severe threat should be greatest during the late
   afternoon and early evening.

   ..Broyles/Thornton.. 04/27/2024

 

[ElectricStorm]

Honestly this is the most concerned I've been for an event in this area since 2019. This might get very very ugly...

[snowlover2]

You get the feeling with that wording that a high risk area is eventually coming.

[ElectricStorm]

Just now, snowlover2 said:

You get the feeling with that wording that a high risk area is eventually coming.

If we wake up and there's not much morning convection I wouldn't be surprised

[Ingyball]

14 million people in the sig tor region. The impacts could be very widespread. 

[Neoncyclone]

Now that is what dryline initiation is supposed to look like!

[Neoncyclone]

 

 

Didn't even notice the 45% sig for hail

 

Edited April 27 by Neoncyclone

[StLweatherjunkie]

4 hours ago, snowlover2 said:

Day 1 moderate.

Displacing the moderate risk so far southeast/east of the triple point/dry line seems difficult to justify with fundamental meteorology. Overall I think CIPS analogs have a much better handle on the threat area and the 80%+ probabilities strongly suggest a high risk is justified. 13 of the top 15 analogs should have been high risk days ... This event is a prime example of why humans should not be generating these outlooks. Let the AI take the wheel and have humans describe and quality control their output.

Edited April 27 by StLweatherjunkie

[Ingyball]

30 minutes ago, StLweatherjunkie said:

Displacing the moderate risk so far southeast/east of the triple point/dry line seems difficult to justify with fundamental meteorology. Overall I think CIPS analogs have a much better handle on the threat area and the 80%+ probabilities strongly suggest a high risk is justified. 13 of the top 15 analogs should have been high risk days ... This event is a prime example of why humans should not be generating these outlooks. Let the AI take the wheel and have humans describe and quality control their output.

I targeted northern Kansas/southern Nebraska for our severe challenge for that reason. And yeah, I like the positioning of the CIPS in this case. The SPC forecasts have been a bit too far east through this pattern.

 

Edit: I will say that I think that there is some balance between pure AI and pure human generation. I think having some human tweaking of AI generation is a good middle ground and prevents moderate or high risk spam when parameters are impressive but a stout cap is present. CIPS and CSU can catch onto that on day 1 and 2, but beyond day 2, they sometimes overdo those outlooks, like 4/15 for example. 

Edited April 27 by Ingyball

[voltwaffle]

First watch of the day is here.
https://www.spc.noaa.gov/products/watch/ww0144.html

I feel like this is gonna be a crazy day.

[ElectricStorm]

From an SPC forecaster 😬

 

 

[StormfanaticInd]

Feels suspect here in Indiana like it might storm. Hmmm

With deep shear to 40 knots combined with the instability, would not

rule out a strong or marginally severe thunderstorm this afternoon,

mainly over the upper Wabash Valley.

Edited April 27 by StormfanaticInd

[StormfanaticInd]

It's already very favorable in Okc

[Ingyball]

Already got some fairly organized cells going. 

[ak9971]

Storm NW of OKC near Kansas border is really starting to organize and is tornado warned. Storms starting to initialize farther to the SW. GOES 16 is always mesmerizing. 

 

[snowlover2]

Quote

 Mesoscale Discussion 0539
   NWS Storm Prediction Center Norman OK
   1057 AM CDT Sat Apr 27 2024

   Areas affected...Northwest TX...western/northern OK...and southeast
   KS

   Concerning...Tornado Watch 144...

   Valid 271557Z - 271730Z

   The severe weather threat for Tornado Watch 144 continues.

   SUMMARY...Severe threat will further increase into the afternoon
   from parts of northwest Texas into southeast Kansas, including
   potential for a couple strong tornadic supercells. A broader tornado
   and/or multiple PDS/non-PDS tornado watches will be needed prior to
   the 18Z expiration of WW 144.

   DISCUSSION...Surface analysis placed the nearly stationary dryline
   across the eastern TX Panhandle through northwest TX. The deepest
   convection is ahead of the dryline in west-central to north-central
   OK, which includes a supercell in cluster and a downstream discrete
   supercell. Surface warming has been more pronounced in parts of
   central OK, generally along and east of the I-35 corridor. The
   leading discrete supercell should have relatively uninterrupted
   inflow as it impinges on this relatively max in boundary-layer
   warming. Amid a 45-kt southerly low-level jet per the TLX VWP data,
   potential will exist for cyclic tornadoes that may be strong. Strong
   mid-level rotation has also been noted with the supercell in cluster
   now centered in Dewey County, OK, and this storm should pose a
   continued threat for all hazards. 

   Additional storms should regenerate along the dryline farther south
   into northwest TX through the afternoon given minimal MLCIN. With
   weaker forcing for ascent relative to farther north, there is some
   uncertainty in how quickly this activity will become severe. But the
   overall environment will favor discrete supercell development,
   especially as the boundary layer further warms.

   ..Grams.. 04/27/2024

 

[ak9971]

Surface based CAPE already above 4000 in OK. Expect to see things start ramping up in a few hours. 

[snowlover2]

Can't remember the last time it was said in an MD that a PDS watch is possible.

[Neoncyclone]

Wow.. here's the new nadocast. This isnt even the absolutrly calibrated(which always overhypes).

[ak9971]

Been quite awhile since an event like this in OK. Hoping for a bust. 

[snowlover2]

Updated day 1 keeps it at moderate.

[snowlover2]

Quote

 Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1125 AM CDT Sat Apr 27 2024

   Valid 271630Z - 281200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   AND EVENING ACROSS PORTIONS OF SOUTHERN KANSAS...MUCH OF
   OKLAHOMA...AND NORTHWEST TEXAS....

   ...SUMMARY...
   Severe thunderstorms are likely today and tonight across the
   southern and central Plains into the lower to mid Missouri Valley.
   The most numerous/intense storms are expected from north Texas into
   Oklahoma and southeast Kansas, where strong tornadoes, very large
   hail of 2-3 inches in diameter and damaging winds of 60-80 mph are
   all possible.

   ...A regional outbreak of severe thunderstorms is forecast for this
   afternoon and evening across parts of KS/OK.  Very large hail and
   strong tornadoes are possible..

   ...OK/northwest TX/south-central KS...
   Water vapor imagery shows the main upper trough is still back over
   southern AZ, with a rapidly ejecting mid/upper level jet streak
   nosing into OK/TX.  This lead feature has aided in the development
   of severe storms this morning over parts of west TX/OK.  Storms will
   develop northeastward through the afternoon into central KS, despite
   an expansive anvil shield from the morning convection.  These storms
   will pose a risk of very large hail and a few tornadoes through the
   afternoon and early evening.

   Farther south, the air mass across much of central/western OK and
   northwest TX continues to warm/destabilize as temperatures rise
   through the mid/upper 70s - eliminating CINH.  Only weak upper
   forcing through the afternoon will result in chaotic development of
   discrete supercells in a very strongly sheared and very unstable
   environment.  Forecast soundings show very steep mid-level lapse
   rates, ample low-level moisture, and strong/increasing shear
   profiles through the day.  Details of timing and location are
   nebulous, but those storms that develop will pose a risk of very
   large hail and strong and possibly long-track tornadoes.  The
   stronger large-scale forcing will arrive around/after dark, with a
   greater eastward surge of storms across central OK expected.  This
   activity may organize upscale in bowing segments will an increasing
   risk of damaging winds along with hail and tornadoes into southeast
   KS and northeast OK tonight.

   ...Southeast CO into northern KS...
   A rather strong surface boundary extends from southeast CO across
   much of northern KS.  Relatively strong heating along this boundary
   and moderate instability will lead to scattered thunderstorm
   development by mid-afternoon along the entire corridor.  Steep
   mid-level lapse rates, strong deep-layer shear, and favorable
   low-level wind profiles in vicinity of the boundary will pose a risk
   of very large hail and a few tornadoes through the afternoon and
   early evening.  This activity is expected to build eastward this
   evening along the same boundary into parts of southern IA/northern
   MO, with a continued risk of large hail along with an increasing
   threat of damaging winds.

   ..Hart/Jewell.. 04/27/2024

 

[ElectricStorm]

I guess there's still a chance things go linear pretty quickly later on which is probably the only thing left that can hold this back and prevented an upgrade so far 

[snowlover2]

And this is outside the moderate risk for the most part.

Quote

 URGENT - IMMEDIATE BROADCAST REQUESTED
   Tornado Watch Number 145
   NWS Storm Prediction Center Norman OK
   1150 AM CDT Sat Apr 27 2024

   The NWS Storm Prediction Center has issued a

   * Tornado Watch for portions of 
     Central and Northeast Kansas
     Southeast Nebraska

   * Effective this Saturday morning and evening from 1150 AM until
     700 PM CDT.

   * Primary threats include...
     A few tornadoes and a couple intense tornadoes likely
     Widespread large hail and scattered very large hail events to
       2.5 inches in diameter likely
     Scattered damaging winds likely with isolated significant gusts
       to 75 mph possible

   SUMMARY...Thunderstorms will develop across parts of central and
   northeast Kansas through the afternoon in a very moist and unstable
   environment.  The strongest cells will be supercells capable of very
   large hail and tornadoes.  A few strong tornadoes are possible.

   The tornado watch area is approximately along and 80 statute miles
   east and west of a line from 70 miles west northwest of Saint Joseph
   MO to 25 miles southeast of Medicine Lodge KS. For a complete
   depiction of the watch see the associated watch outline update
   (WOUS64 KWNS WOU5).

   PRECAUTIONARY/PREPAREDNESS ACTIONS...

   REMEMBER...A Tornado Watch means conditions are favorable for
   tornadoes and severe thunderstorms in and close to the watch
   area. Persons in these areas should be on the lookout for
   threatening weather conditions and listen for later statements
   and possible warnings.

   &&

   OTHER WATCH INFORMATION...CONTINUE...WW 144...

   AVIATION...Tornadoes and a few severe thunderstorms with hail
   surface and aloft to 2.5 inches. Extreme turbulence and surface wind
   gusts to 65 knots. A few cumulonimbi with maximum tops to 500. Mean
   storm motion vector 25030.

   ...Hart

Quote

Tornadoes

Probability of 2 or more tornadoes	High (70%)
Probability of 1 or more strong (EF2-EF5) tornadoes	Mod (60%)

Wind

 

Probability of 10 or more severe wind events	Mod (60%)
Probability of 1 or more wind events > 65 knots	Mod (30%)

Hail

 

Probability of 10 or more severe hail events	High (80%)
Probability of 1 or more hailstones > 2 inches	High (80%)

Combined Severe Hail/Wind

 

Probability of 6 or more combined severe hail/wind events

High (>95%)

 

Edited April 27 by snowlover2

[Neoncyclone]

As the warm-front continues to lift I think the storms that form on it have some serious potential. All it takes is one look at the 0-3km ML CAPE sfc vorticity cheat sheet.