4/2-4/3 Potential Major Severe WX Outbreak

[Geoboy645]

Over the last day or so, the Models have really zeroed in on a potentially major severe weather outbreak across the sub forum.  Figured that there should be a thread for it considering it's only 4-5 days out.

[nvck]

keep in mind that this is a composite of all hazards but still, looking like another big day in the area.

[nvck]

Quote

With ascent along the front somewhat modest as stronger large-scale
   ascent focuses northward into the western Upper Great Lakes and into
   Ontario, storm mode may tend toward isolated storms, as opposed to
   more linear development.  This, combined with flow that is forecast
   to weakly veer but dramatically strengthen with height, suggests a
   primarily supercell storm mode.  In additional to very large hail
   (particularly with southward extent), widespread damaging winds and
   several tornadoes are expected, some possibly significant.  Risk is
   expected to continue well into the evening and likely overnight,
   shifting slowly eastward across the Midwest and mid/lower
   Mississippi Valley through the end of the period.

From the day4 portion of the days 4-8 outlook

[Radtechwxman]

Im just not overly impressed by this setup and definitely not feeling as aggressive as spc is. Low deepens quick Tues and is well into occlusion process by Wed. Low also very far north. There is good flow over warm sector but feel like sfc winds will tend to veer without secondary low development. Models look very linear right now and morning convection could definitely be an issue esp with northward extent. It does look more cellular further south and there is some orthogonal nature to shear vectors off CF. But the more south you go, the more removed from the low you are. Just not 100% on board with a big tornado threat yet. 

[Spartman]

JB considering this upcoming outbreak as part of the "busiest period" since 2011

https://x.com/BigJoeBastardi/status/1906358608062788036

[KeenerWx]

Looking like this might be a dud locally, with better chances south & east. 

[Spartman]

2 hours ago, KeenerWx said:

Looking like this might be a dud locally, with better chances south & east. 

Models and even NBM had the high rainfall amounts locked in for the past several days, if not at least a week.

[sbnwx85]

Large Day 3 Enhanced Risk. Fairly strong wording from SPC.

Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0241 AM CDT Mon Mar 31 2025

   Valid 021200Z - 031200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM THE LOWER
   GREAT LAKES THROUGH THE MID MISSISSIPPI VALLEY AND THE ARKLATEX...

   ...SUMMARY...
   An outbreak of severe storms is possible Wednesday and Wednesday
   night from the Lower Great Lakes, the Mid MS Valley and the
   ArkLaTex. Severe wind gusts, very large hail, and significant
   tornadoes are expected.

   ...Synopsis...
   A powerful, negative tilt, upper trough will move out of the Plains,
   over the Midwest and into the Great Lakes Wednesday. Accompanied by
   a 100+ kt jet streak, very strong forcing for ascent will overspread
   a large unstable warm sector from the Great Lakes, OH Valley and MS
   Valley. A strong cold front will sweep eastward with widespread to
   numerous thunderstorms expected. 

   An outbreak of widespread severe storms including: significant
   tornadoes, severe wind gusts and very large hail is possible
   Wednesday and Wednesday night.

   ...Midwest to the lower Great Lakes and OH Valley...
   Early in the forecast period, one or more clusters of thunderstorms
   are likely to be ongoing across portions of KS/MO into the upper MS
   Valley. Very strong synoptic ascent at the exit region of the H5 jet
   may allow these storms to persist through the morning as the air
   mass downstream slowly destabilizes. Re-intensification is possible
   as storms move farther northeast into the lower Great Lakes by early
   to mid afternoon. Depending on the timing, these storms may also
   outrun the warm sector. This could limit the severe potential to
   points farther south if the airmass is unable to recover.
   Regardless, very strong effective shear (60-80 kt) and large
   hodographs would support organized storms capable of significant
   damaging winds, and a tornado risk.

   ...Mid MS Valley...
   Immediately southeast of the primary upper low track, more subtle
   forcing for ascent will overspread a rapidly moistening air mass
   across the Ozarks, eastern OK and the Mid MS Valley. The air mass
   will rapidly destabilize and become uncapped with MLCAPE of
   1500-2500 J/kg likely by mid to late morning. Storms are likely to
   form by midday as ascent overspreads a pre-frontal trough/diffuse
   dryline. Some boundary parallel flow is likely suggesting a mixed
   mode of cellular and bowing segments. However, the very strong
   troposphereic shear profiles, courtesy of a 50+ kt low-level jet,
   favor significant supercells as the primary storm mode. A secondary
   surface low will serve to further back low-level flow and expand
   very large hodographs from the late afternoon into the evening
   hours. Very large hail, significant tornadoes and damaging winds all
   appear likely. The severe threat will continue overnight with some
   upscale growth across the Mid MS/TN Valley within the broadly
   unstable air mass. 

   Consideration was given to higher severe probabilities across parts
   of the Mid MS Valley for the potential for multiple long-lived
   significant supercells. However, confidence in the exact storm mode
   and location of maximum threat remains unclear given some potential
   for morning convection and model timing variance.

 

[CheeselandSkies]

Again, still somewhat skeptical on this as a widespread/significant outbreak which is why I think SPC was wise to hold off on an initial Day-3 Moderate. I could easily see a scenario where the northern part of the risk area (a.k.a. us) gets borked by morning convection and the southern part by veered low-level winds and outflow interactions (like yesterday).

[CheeselandSkies]

As I suspected; latest NAM crashed way down on the forecast EHI/STP values over northern Illinois compared to just 0Z last night.

[sbnwx85]

Yikes.

[vortex]

6 hours ago, CheeselandSkies said:

As I suspected; latest NAM crashed way down on the forecast EHI/STP values over northern Illinois compared to just 0Z last night.

18z brings it back. 

[CheeselandSkies]

9 minutes ago, vortex said:

18z brings it back. 

...and with more favorable timing, at that (triple point pushing in at closer to 21Z instead of 18Z). A frustrating amount of flip flopping for inside of 48 hours from the event.

[cyclone77]

Another poorly timed event for the DVN cwa.  Maybe some elevated hailers in the morning.

[largetornado]

While the severe threat is noteworthy, i feel like the flooding potential for the southern subforum could be catastrophic. 6-10" of rain along the ohio river from missouri to cincinnati.

[CheeselandSkies]

It's the first run to come in range, but 0Z HRRR washes out the northern IL portion of the setup with a big MCS (left over from what develops tomorrow evening) Wednesday morning. However, it does break out a few dangerous-looking supercells along the Ohio River by 23-00Z.

[MidwestChaser]

my area Wednesday evening: