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Severe WX Severe Weather 4/11 - 4/15

Grand Poo Bah said:
Don't get me wrong. We've got some serious potential for a high-end event here, but this setup is about as boom or bu$t as it gets. In the areas with the most potential it's possible the cap holds and nothing happens at all. In fact, that's the more likely outcome at the moment based on current model guidance. These hype casters are gambling with the general public's trust, and they don't even have the courtesy to do it with good odds. They could seriously just wait a day or two, and make these predictions with higher confidence, but they can't go a single day without trying to be the center of every weather event.

We have real-world evidence that alarm-fatigue is real, and people take warnings less seriously after too many false alarms. SPC and NWS policy on this stuff is written in blood. We've already learned these lessons. Max is just too young and has gotten too greedy to understand them, or he just doesn't care. It's hard to tell at this point. I have a hard time assuming good intentions from someone who uses phrases like "Oh No", "Not Good", and "This is Bad" on every single Youtube thumbnail.
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All this being said, I'm very anxiously awaiting the HRRR and RAP getting into range tomorrow. Looked at the 00z NAM, and it just keeps getting more and more absurd with every run. It's also showing a nocturnal event Tuesday evening.

Edit: I can't find any soundings this run where the cap is totally eroded though, so that's a good sign.
 
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Grand Poo Bah said:
All this being said, I'm very anxiously awaiting the HRRR and RAP getting into range tomorrow. Looked at the latest NAM, and it just keeps getting more and more absurd with every run. It's also showing a nocturnal event Tuesday evening.
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rrfs is barely in range, but its rrfs, so id take this with a grain of salt. still interesting to see.
 
jackhutwx said:
View attachment 52727


rrfs is barely in range, but its rrfs, so id take this with a grain of salt. still interesting to see.
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Take it with the whole salt shaker. The NWS likes the RRFS because it does the best with storm location, but it's terrible with storm mode. We'd probably be at 1000 tornadoes already for the year if even half the supercells the RRFS prints verified. However, the 32km NAM does seem to be agreeing with the timing and general location of this convection, so it's definitely something to watch. We'll have more definitive answers very soon.
 
1775978712196.png1775978723410.png

...SUMMARY...
Isolated to scattered severe thunderstorms are expected on Tuesday and Tuesday night from the Southern Plains to the Great Lakes.

...Synopsis...

Southwesterly deep-layer flow will persist from the southern Plains to the Great Lakes on Tuesday. An upper trough over the western U.S. will slowly pivot eastward, emerging over the central/southern High Plains by Sunday morning. Surface low pressure will remain centered over the central Plains, with troughing extending southwestward into west TX. A cold front will slowly sag southward across portions of the Upper Midwest/Great Lakes vicinity. The surface trough/dryline and the boundary across the Great Lakes will become a focus for thunderstorm activity through the forecast period.

...Lower MO Valley to the Great Lakes vicinity...

Convection may be ongoing across portions of the region Tuesday morning. This activity should spread east, and persistent warm advection should allow for airmass recovery during the afternoon. Steep midlevel lapse rates will overspread mid 60s F dewpoints, and moderate to strong destabilization is forecast. Stronger height falls are not expected across the region, as the main upper trough will be focused well to the southwest. However, warm advection atop a southward-sagging surface boundary should support isolated to scattered storm development by late afternoon/evening. Supercell wind profiles are evident in forecast soundings, suggesting an all-hazards risk. Given uncertainty related to potential airmass contamination from early day convection and cloud cover, and potential capping concerns, will maintain Slight risk (level 2 of 5). However, a rather volatile thermodynamic and kinematic environment will exist across portions of the region, and higher probabilities may be needed in subsequent outlooks depending on forecast trends and mesoscale details.

...Southern Plains vicinity...

Large-scale ascent will begin overspreading the region by late afternoon/evening as the western upper trough finally begins to eject eastward. As this occurs, mixing and convergence along a surface dryline should support at least isolated storm development by around 00z. Steep midlevel lapse rates and mid/upper 60s F dewpoints will support strong destabilization amid supercell wind profiles. Large to very large hail will be possible in addition to strong wind gusts and a tornado or two.
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06z hrrr shows a doomsday scenario for Wisconsin as it models multiple renegade supercells riding along the warm front in a extreme kinematic environment.
Thankfully this is two days out which means in terms of cam models, and in this particular context, out in fantasy land.
So Im not even going to bother showing the soundings.
 
jiharris0220 said:
06z hrrr shows a doomsday scenario for Wisconsin as it models multiple renegade supercells riding along the warm front in a extreme kinematic environment.
Thankfully this is two days out which means in terms of cam models, and in this particular context, out in fantasy land.
So Im not even going to bother showing the soundings.
Click to expand...
12z HRRR showed this too, but of course in fantasy land.

Interesting threat for tornadoes today in MN/WI, models have been very blunt that convection may struggle to develop this far north. If a supercell or two taps into this kinematic environment of 260+ 0-1km SRH or so, i would wonder if a strong tornado couldn't be ruled out. That 2% CIG1 probably needs to be extended a bit south. I think the possibility of cells initiating are pretty low given robust dry slot + warmer temps aloft, and they may be elevated if they DO develop.

The MCS in Texas currently may be our best opportunity for any tornadic activity down south here, i personally believe mid level subsidence will likely prevent any cells on the dryline today. Of course, it does appear elevated so chances are pretty low that a tor comes out of it. It already produced a couple last night in Texas.

Given how the EURO performed last night on a tricky, MCV driven type setup, using it for these days improved my confidence for these solutions a bunch.

I expect storm mode to be more messier on Monday, but there's a isolated window for a more discrete supercell to cause issues including significant hail if north of the WF or a conditionally significant tornado threat.

Models have really been all over the place with this sequence
 
I’m just not overly impressed with any of the upcoming set ups. They’re all very conditional, and model variance isn’t making this any simpler. The SPC are playing these set ups very conservative as well. Regarding the previous headliner day, Positive tilted troughs can and do lift and cool caps, but they’re usually way more zonal, and it requires a different geometric configuration than what is currently being modeled. Some of the depictions really remind me of 4/28 of last year. Strung out and not well defined trough and jet.

Now, I’m more talking about things from the synoptic level, rather than reliance on surface boundaries for CI and storm maintenance (warm front will once again be in play this week).

There will be tornados this week, I just think the higher end solutions over a broad swath that had that “look” last week, are capped (ha!) for this one.
 
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