It’s time to visit Sunday again (we’ll try to get another blog out on the morning of). Overall, I still think a tornado risk will be present in the early evening with probably several tornado warnings. However, the main severe threat might end up being damaging winds with this one.

We finally have some higher resolution guidance and more models having a look at the setup so let’s dive in.

Big, Fast Moving System

The amount of forcing quickly ejecting over an unstable airmass is impressive on Sunday. The system quickly ramps up lift after mid afternoon and towards sunset. Depending on cap strength and moisture return, we’ll see storms form around 4 p.m. on Sunday give or take an hour or two.

The center of the upper system is back in New Mexico in the mid-late afternoon but will already be impacting the environment by then.
By sunset, forcing will become overwhelming with a line of storms becoming very likely by then.

Moisture Return?

This setup is a great primer for analyzing the evolution of an atmosphere over time. On the Plains, moisture quality and depth is everything. In the wake of this week’s arctic front, getting that warm and unstable air back north will require some work by the atmosphere.

  • Right now, models continue to run too warm on the temperatures behind the front, meaning they are modifying it a bit too quickly.
  • The NAM on the other hand, which has been the outlier on very poor moisture return, seems to be holding onto the arctic airmass a bit too long.
  • I think you have to split the difference a bit. This is a situation where looking at the SREF is a good idea.
The SREF is not very bullish on getting 60 dewpoints back over the dryline (or even east of it) by Sunset on Sunday. This is a sign that moisture return will likely be slightly slower than the more bullish models are projecting.
I feel obligated to share a model graphic of a more bullish model anyways to show that, in the best case scenarios outlined by models, there are sub 60 dewpoints around 30-100 miles east of the dryline on Sunday.

Storm Mode

Another thing to question for setups at this range that you can reasonably start answering is what mode will storms be in? This is important because a more linear mode is less favorable for stronger tornadoes *generally*. QLCS tornado events are real and dangerous, but from a storm chasing perspective I’ll just say they’re much less interesting.

The FV3 has scattered storms forming 22-23z (that’s 4-5 p.m.) across Kansas into Northwest Oklahoma. This is a sign the forcing is hitting fast and quick like the upper charts do suggest.
By 6 p.m. (and towards sunset) storms are already beginning to crowd up and become more linear. Experience says these types of setups usually give you 1-2 hours of semi-isolated modes but a line does quickly take over as the dominant storm mode.

The Overall Environment

There are several things which lead me to believe this environment is pretty standard for an early season setup. Moisture return is in question, and the location where the best airmass is will likely only experience storms for an hour or so as they form. Lower instability setups on the Plains (especially as you go below 1500 MLCAPE) tend to take a bit to get going, and they also tend to not be visually impressive.

A box sounding on the dryline reveals an impressively sheared environment with good moisture aloft. With slightly less surface moisture that ensembles are showing, instability really hits in that less than or right at 1000 j/kg range. But the 0-1km helicity of greater than 250 with impressive 0-6km shear of 75kt is on the high end. I do want to point out the storm motions though, right movers are 55-60mph forward motions on forecast soundings.

The Bottom Line

Storms, and a line of storms, are a sure bet on Sunday. Given the amount of low-level shear, tornadoes are also going to be a risk, especially from 6-9 p.m. Damaging winds will probably be the main risk with the line, which should slowly weaken starting 8-9 p.m.

  • However, the storm chaser ‘pretty supercell’ and ‘supercell tornado’ index is not very high for Sunday.
  • Storm motions all but guarantee storms move into a less unstable airmass within an hour or two and they’ll likely be crowded and line out fast too.
  • Chaser traffic isn’t often a problem with storm chasing but this time might be one of the exceptions. The fast storm motions are admittedly a nightmare for chasing with any traffic also on the roads.
  • This setup is a slightly better version of the last one that produced a couple of tornado warned supercells embedded in a line for a brief bit in S/SE OK.