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Severe WX Severe Weather Threat 3/14-3/16

wx_guy said:
Here is a large box sounding from the 18z NAM that encompasses all of central and eastern MS and all of western AL (seeing a pattern here?). I asked ChatGPT to give an unbiased, somewhat technical, and frank public message concerning this. Its output is below. It's not mincing words.

View attachment 35216





Severe Weather Analysis and Forecast – March 15, 2025​

Synoptic Overview & Sounding Analysis:
The provided NAM forecast sounding for 21Z on March 15, 2025, captures a large domain across central/eastern Mississippi and western Alabama, encompassing a highly sheared, strongly unstable pre-convective environment conducive to tornadic supercells.

Thermodynamics:

  • MLCAPE: 1,758 J/kg – Sufficient for robust updrafts, especially with deep-layer shear in place.
  • 3CAPE: 91 J/kg – Favorable for near-ground stretching, enhancing tornado potential.
  • SFC Temperature / Dewpoint: 67°F-70°F / ~60°F – Warm, moist boundary layer supporting buoyant parcels.
  • LCL / LFC Heights: 655m / 1,140m – Very low LCLs favor tornadogenesis, particularly in high-shear regimes.
  • Mid-Level Lapse Rates: 7.7°C/km – Moderately steep, indicating strong mid-level cooling aloft.
  • PWAT: 1.51” – Ample moisture for sustained convection.
  • DCAPE: 800 J/kg – Sufficient for strong downdraft potential, suggesting a risk for damaging RFD surges.
Kinematics:

  • 0-1km Shear: 35 kt
  • 0-1km SRH: 355 m²/s² – Strongly supportive of low-level mesocyclones.
  • 0-3km SRH: 444 m²/s² – Further indicative of robust streamwise vorticity ingestion.
  • 0-6km Shear: 78 kt – Easily supports organized supercells with strong mid-level rotation.
  • Critical Angle: 55° – Favorable for streamwise vorticity ingestion and efficient tornadogenesis.
Supercell Composite & STP (Significant Tornado Parameter):

  • Supercell Composite: 15.6 – Strongly indicative of long-lived supercells.
  • STP (fixed): 4.2 – High-end values associated with significant tornadoes.
  • Effective Layer STP: Probability of EF2+ tornadoes at ~0.25-0.32, indicating a marked potential for strong tornadoes.
Analog Guidance:

  • The SARS dataset indicates a 67% match to past significant tornado outbreaks, further reinforcing the risk for violent tornadoes.

Forecast & Public Discussion: <EDIT: THIS IS NOT REAL, IT'S CHAT GPT SIMULATED MSG!!!>​

…SEVERE WEATHER OUTBREAK EXPECTED ACROSS THE DEEP SOUTH ON SATURDAY…
…POTENTIALLY LONG-TRACK TORNADOES POSSIBLE…

An extremely volatile environment will be in place across central/eastern Mississippi and western Alabama on Saturday, March 15. Forecast soundings depict a classic high-shear, high-CAPE setup with a strongly veering wind profile, deep low-level moisture, and very favorable tornado-supportive hodographs.

Thunderstorms will initiate along a surface boundary by mid-afternoon and quickly become discrete supercells, given 80+ kt deep-layer shear. Given 0-1km SRH exceeding 350-400 m²/s², multiple strong to violent tornadoes (EF2-EF4+) appear possible, particularly in the vicinity of the I-20 corridor.

Public Call to Action:
Residents in the highlighted region must have a severe weather plan in place. These types of setups are rare and can produce deadly tornadoes, particularly after dark. Ensure you have multiple ways to receive warnings, and be prepared to shelter immediately if a tornado warning is issued for your area. The combination of instability, moisture, and shear suggests that a high-end tornado outbreak is a distinct possibility.

Stay tuned for updates from the SPC, NWS, and local meteorologists. This is a life-threatening situation.
Click to expand...
67% SARS match for significant tornado outbreaks. That's rather impressive.
 
Pretty new and very concerning development. NAM is now showing 1500-2000 J/kg of SB cape reaching all the way up into southern Minnesota ahead of the 974 mb low Friday evening.

1741817866738.gif

Soundings from southeast and central Iowa (not contaminated).

1741817946900.png1741817997083.png


West Illinois (not contaminated
1741818843030.png

Dew points up north are getting dangerously close to the 60+ degrees they need to start causing problems as well.

1741818523621.gif

GFS still doesn't agree on Dew Points getting above the low 50s, but it has started to show the increased northern CAPE.

1741819890892.gif

All that is to say Friday is shaping up into something extraordinary. Huge credit to the SPC with their forecasting this morning. Wouldn't doubt if Iowa is added to the hatched risk tomorrow depending on which way dew points trend on the next few runs.
 
Last edited:
vemir said:
New to this forum. I'm curious to hear peoples opinions on potential fail modes for this event (particularly sat), specifically regarding lack of cap/EML causing storms to fire off early and tampering the environment. Correct me if this is a non-issue
Click to expand...
Welcome! This has been answered by mets earlier in the thread, but there looks to be plenty of cap and EML and certain models like the Euro are likely over-convecting.
 
wx_guy said:
Here is a large box sounding from the 18z NAM that encompasses all of central and eastern MS and all of western AL (seeing a pattern here?). I asked ChatGPT to give an unbiased, somewhat technical, and frank public message concerning this. Its output is below. It's not mincing words.

View attachment 35216





Severe Weather Analysis and Forecast – March 15, 2025​

Synoptic Overview & Sounding Analysis:
The provided NAM forecast sounding for 21Z on March 15, 2025, captures a large domain across central/eastern Mississippi and western Alabama, encompassing a highly sheared, strongly unstable pre-convective environment conducive to tornadic supercells.

Thermodynamics:

  • MLCAPE: 1,758 J/kg – Sufficient for robust updrafts, especially with deep-layer shear in place.
  • 3CAPE: 91 J/kg – Favorable for near-ground stretching, enhancing tornado potential.
  • SFC Temperature / Dewpoint: 67°F-70°F / ~60°F – Warm, moist boundary layer supporting buoyant parcels.
  • LCL / LFC Heights: 655m / 1,140m – Very low LCLs favor tornadogenesis, particularly in high-shear regimes.
  • Mid-Level Lapse Rates: 7.7°C/km – Moderately steep, indicating strong mid-level cooling aloft.
  • PWAT: 1.51” – Ample moisture for sustained convection.
  • DCAPE: 800 J/kg – Sufficient for strong downdraft potential, suggesting a risk for damaging RFD surges.
Kinematics:

  • 0-1km Shear: 35 kt
  • 0-1km SRH: 355 m²/s² – Strongly supportive of low-level mesocyclones.
  • 0-3km SRH: 444 m²/s² – Further indicative of robust streamwise vorticity ingestion.
  • 0-6km Shear: 78 kt – Easily supports organized supercells with strong mid-level rotation.
  • Critical Angle: 55° – Favorable for streamwise vorticity ingestion and efficient tornadogenesis.
Supercell Composite & STP (Significant Tornado Parameter):

  • Supercell Composite: 15.6 – Strongly indicative of long-lived supercells.
  • STP (fixed): 4.2 – High-end values associated with significant tornadoes.
  • Effective Layer STP: Probability of EF2+ tornadoes at ~0.25-0.32, indicating a marked potential for strong tornadoes.
Analog Guidance:

  • The SARS dataset indicates a 67% match to past significant tornado outbreaks, further reinforcing the risk for violent tornadoes.

Forecast & Public Discussion: <EDIT: THIS IS NOT REAL, IT'S CHAT GPT SIMULATED MSG!!!>​

…SEVERE WEATHER OUTBREAK EXPECTED ACROSS THE DEEP SOUTH ON SATURDAY…
…POTENTIALLY LONG-TRACK TORNADOES POSSIBLE…

An extremely volatile environment will be in place across central/eastern Mississippi and western Alabama on Saturday, March 15. Forecast soundings depict a classic high-shear, high-CAPE setup with a strongly veering wind profile, deep low-level moisture, and very favorable tornado-supportive hodographs.

Thunderstorms will initiate along a surface boundary by mid-afternoon and quickly become discrete supercells, given 80+ kt deep-layer shear. Given 0-1km SRH exceeding 350-400 m²/s², multiple strong to violent tornadoes (EF2-EF4+) appear possible, particularly in the vicinity of the I-20 corridor.

Public Call to Action:
Residents in the highlighted region must have a severe weather plan in place. These types of setups are rare and can produce deadly tornadoes, particularly after dark. Ensure you have multiple ways to receive warnings, and be prepared to shelter immediately if a tornado warning is issued for your area. The combination of instability, moisture, and shear suggests that a high-end tornado outbreak is a distinct possibility.

Stay tuned for updates from the SPC, NWS, and local meteorologists. This is a life-threatening situation.
Click to expand...
The temperature and dewpoints are certainly warm and moist enough.
 
Grand Poo Bah said:
Dew points up north are getting dangerously close to the 60+ degrees they need to start causing problems as well.
Click to expand...
Dew points don't have to be above 60 degrees for there to be problems. There are plenty of strong and even violent tornadoes such as the Winterset, Iowa EF4 that have occurred with dewpoints under 60. Due to the presence of cold air aloft, there is plenty of CAPE available in these areas with lower than 60s dewpoints which is more than enough for storms to work with.

That's why I've been concerned with this northern area too, because if models are under-forecasting dewpoints and moisture depth even a little bit, there's plenty of energy for storms to work with so they won't get ripped apart by the shear.
 
Slightly off topic, but an important statistic I simply can't share enough.

4 of the top 7 most numerous 24 hour tornado outbreaks have occurred in the 2020s. If you remove the huge outliers of 1974 and 2011, the 2020s hold the top 3 spots, and 4 of the top 5 spots. Regardless of how bad this storm is on Friday/Saturday, it's starting to become undeniable this is the new normal.

1741820790966.png
 
Grand Poo Bah said:
Slightly off topic, but an important statistic I simply can't share enough.

4 of the top 7 most numerous 24 hour tornado outbreaks have occurred in the 2020s. If you remove the huge outliers of 1974 and 2011, the 2020s hold the top 3 spots, and 4 of the top 5 spots. Regardless of how bad this storm is on Friday/Saturday, it's starting to become undeniable this is the new normal.

View attachment 35221
Click to expand...
Also needs to be pointed out that we have gotten way better at surveying for them as well
 
cincywx said:
dualpol has also made it easier to detect weaker tornadoes compared to the pre-dualpol era, which was as recent as 15 years ago.
Click to expand...
yeah, imagine 4/27/11 with dual-pol would have made stuff sooo much easier, considering Cc didn't exist till like late 2012/early 2013 I think

still did a phenomenal job with the current radar tech at that time
 
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