• Welcome to TalkWeather!
    We see you lurking around TalkWeather! Take the extra step and join us today to view attachments, see less ads and maybe even join the discussion.
    CLICK TO JOIN TALKWEATHER

Severe WX Severe Weather 4/24-4/26

I'd say that tomorrow is either major hail and sig wind or a supercell taps into the strong low level shear tomorrow and maybe produce a strong tornado or two. Thermodynamically, very impressive wth 4K SBCAPE, well balanced spreads. Significant all hazards are easily possible.

Sunday continues to look like a parameter space capable of a potentially significant tornado threat should supercells develop in E OK. But I would definitely argue the ceiling has let off a bit. Maybe jumped the board initially with this one, ASTORP has kept probs relatively low due to uncertain CI, but if CI trends become more favorable, it'll probably jump straight to a significant tornado threat.

I'm glad to see people utilising ASTORP a bunch now since it is a very helpful tool if it's not tossed around like a SPC product which it isn't. It's depicted quite the picture for Monday and has maintained its MDT ceiling for a few runs now.

Monday continues to look a significant svr event, capable of significant, long track tornadoes across MO/IL/AR. I've tried to remain conservative with this one, but safe to say, this is a parameter space capable of a high end severe weather event. Don't want to exactly go into specifics but this one has genuine potential if we remain untapped in moisture run and continue uptrending kinematics. Latest 18z guidance is pushing me into moderate with this one now. Would not be surprised to see the SPC use very strong wording in later outlooks. Perhaps, even intense tornadoes.
 
Monday has the potential to be a long duration event from the early afternoon to late evening. I'm getting some similarities to a particular April event last year in the same areas, except a bit more extended down south and has a bit more northward extent. Thermodynamically however, it's more potent and that is problematic in itself. Right now, i don't like the trends.
 
WeathermanLeprechaun said:
I'd say that tomorrow is either major hail and sig wind or a supercell taps into the strong low level shear tomorrow and maybe produce a strong tornado or two. Thermodynamically, very impressive wth 4K SBCAPE, well balanced spreads. Significant all hazards are easily possible.

Sunday continues to look like a parameter space capable of a potentially significant tornado threat should supercells develop in E OK. But I would definitely argue the ceiling has let off a bit. Maybe jumped the board initially with this one, ASTORP has kept probs relatively low due to uncertain CI, but if CI trends become more favorable, it'll probably jump straight to a significant tornado threat.

I'm glad to see people utilising ASTORP a bunch now since it is a very helpful tool if it's not tossed around like a SPC product which it isn't. It's depicted quite the picture for Monday and has maintained its MDT ceiling for a few runs now.

Monday continues to look a significant svr event, capable of significant, long track tornadoes across MO/IL/AR. I've tried to remain conservative with this one, but safe to say, this is a parameter space capable of a high end severe weather event. Don't want to exactly go into specifics but this one has genuine potential if we remain untapped in moisture run and continue uptrending kinematics. Latest 18z guidance is pushing me into moderate with this one now. Would not be surprised to see the SPC use very strong wording in later outlooks. Perhaps, even intense tornadoes.
Click to expand...
Yeah, I heard a few days ago abt some of you guys bringing up 5/16/25 and seeing that PAH post of discretes eventually becoming a line kinda confirms that. Lets hope something prevents Monday from being just a larger scale ver of 5/16.
 
Cyclonic Paracosm said:
Yeah, I heard a few days ago abt some of you guys bringing up 5/16/25 and seeing that PAH post of discretes eventually becoming a line kinda confirms that. Lets hope something prevents Monday from being just a larger scale ver of 5/16.
Click to expand...
What could prevent Monday from being a notably high end MS Valley event would be Sunday convecting to the point where leftover convection could hinder Monday even just a little bit more better. It is rare to see this much instability have such a potent overlap with kinematics, and even a large, spatial warm sector with discrete nature to it.
 
KevinH said:
Define multiple? Within what timeframe?
Click to expand...
Definition to Tornado Outbreak Sequence: Continuous or near continuous series of multiple tornado outbreak days, often lasting several days to over a week, generated by a persistent synoptic-scale weather pattern
 
N0mz said:
From the 12z GFS I measured a jet translation speed of 58 !! kts from 4/27 06z to 4/28 00z. Maybe a little extreme but I've attached my work below. Would obviously point to a high-risk event, especially since the jet is basically slamming straight into the risk area.

Click to expand...

I'm pretty sure the center of the jet at 00z 4/28 is more in W IL. You used the nose of the jet moreso in N IL which I got 57 kts for using your method. I used St Louis as the end point and got 47 kts. Regardless, that is still a very potent outcome in terms of jet translation speed.
 
Really good disco from NWS Paducah at 00z:
Synoptically a 110 kt west southwesterly polar/subtropical jet
max works towards the central Plains Sunday. This pinches a
sharp shortwave trough on the leading edge as it marches across
the Plains which by Monday afternoon leads to strongly
directionally diffluent flow from the mid-south to the western
Great Lakes region. A ~995 mb sfc low tracks from southern
Kansas into southern Wisconsin during the day and the low level
height gradient tightens to produce 15-20 kt south to
southwesterly surface winds and 40 to 50 kt 850mb winds. 12z
deterministic GFS output have our surface winds a little more
backed, but I think grid-scale feedback type issues are lowering
sfc pressures along vigorous deep convection a little more than
what is likely to occur. The ECMWF has hints of this too
however. Looking at the 12z ECWMF jet profile the peak Q-vector
convergence/DCVA might be just north of St. Louis, so I think it
is possible that there are a little stronger low level pressure
falls southeast of the parent sfc low that might lead to the
isallobaric response necessary to get that extra little backing
in the surface winds. Rich boundary level moisture is advected
from the Gulf on the strong southwesterly winds and surface
dewpoints are still modeled in the 67-71 degree range over much
of the CWA. The GFS initiates vigorous convection over
southcentral MO about 21z, and the ECMWF is slightly slower with
that. A modest capping inversion remains present in model
forecast soundings, presumably from a weak EML. This cap would
be strong enough to mostly hold back surface based convection
until peak heating. Mid-level lapse rates appear quite
exceptional at 7.5 to even 8 degrees C/km. If you take the
deterministic guidance at face value, over southeast Missouri
you get about 3000-3500 J/kg of MLCAPE with 0-1m SRH 200-250
m2/s with large sweeping hodographs. The rapid changeover of
large scale ascent from neutral to sharply positive might help
support upscaling to linear features fairly quickly, but I am
concerned the weak residual capping inversion might support
supercells. This is still using global model level resolution,
but it is a very concerning setup. Machine learning output and
the Storm Prediction Center have been very consistent with this
event as well and paint a higher level threat than your average
spring severe event.

Potential limiting factors:

This is still modeling a modestly small feature (the peak
diffluence/shortwave) at fairly long meteorological lead times
and shifts in the intensity and area are absolutely still
possible, and even likely. We could end up more in the right
front (convergent) quadrant of the upper jet and struggle to
have convection break out.

The "bullseye" of this event may end up being a fairly small
geographic area that could vary. The strongest impacts could
also vary significantly, we are forecasting 2-4 km scale
processes 84 hours from now, lots could still happen.

We still haven`t seen this with our increasingly high-
performing/useful convection allowing models. Those run out to
about 48 to 60 hours so we still have some time to wait for
that. Having this degree of consistency/concern even 5 to 10
years ago on an event would have been unthinkable.

Sometimes the modeled mid-level lapse rates don`t quite pan out

It`s the weather, weird things happen and we can`t see, measure,
model or consider everything.

More concerning factors:

The model consistency has been very strong with this. High-
impact events often carry a little higher degree of consistency
and this may be one of those instances.

Dewpoints are very rich and that has been consistent.

Model mid-level lapse rates are exceptional.

Shear is very favorable for supercell tornadoes. It would also
be supportive of QLCS tornadoes if more linear features develop.
Click to expand...
 
You must log in or register to reply here.
Back
Top