Widespread Severe Weather Returns to the Plains

An early Summer severe weather outbreak looks to be taking aim at the central plains this weekend into early next week. Severe storms capable of damaging wind and hail, and perhaps a low-end tornado threat although high-based, elevated storms should temper the overall tornado risk, are expected across portions of Oklahoma and Texas eastward. The "peak" of activity appears to be tomorrow (Sunday 24 June) however. A more significant scenario has the potential to unfold across most of Kansas into the Oklahoma/Texas panhandke region. All hazards are possible tomorrow as initial supercells will be capable of tornadoes, large hail, and damaging wind. Through the evening, an intense MCS is expected and extreme wind gusts as well as embedded mesovortices will be possible. A flood threat may develop too if storms end up backbuilding.
From our perspective as chasers we're considering two possible target areas. Target #1 is the sfc-low/triple-point in Southwest KS to the OK panhandle. Target #2 is near Hays, KS along I70.
I'm leaning toward the triple-point play because, for one it's the triple-point, a classic target for us. Also, I feel fairly confident that storms will be more discrete here and the environment should support strong supercellular storms. I'm thinking the cap will break across the panhandle by 21-23z (4-6pm) and this would put us in the vicinity of the "burst point". I'm also somewhat concerned with early-day convection and a possible upstream cluster moving in from Nebraska with the northern target.

A substantial overlap of ingredients favorable for severe storms is suggested in the vicinity of the triple point in southern KS. The area circled in black is the region I'm targeting for supercells and possibly a few tornadoes. (Note: Significant severe weather is possible outside the circled area, that is just the region we are targeting)

Either way, significant storms are expected across the region Sunday with both the initial supercells and the eventual powerful QLCS and anyone in the area should monitor multiple sources of weather information and listen to all watches and warnings.

The Setup

So what is coming together for this fairly noteable late-June severe weather? Unlike the diurnally-driven "pulse" storms that are oh so common this time of year, we actually have a relatively strong upper-low/"kicker" swinging around the Rockies. Normally during the Summer we see extreme instability and very rich atmospheric moisture but weak flow aloft owed to the northern retreat of the polar jet results in high CAPE-low shear setups, in other words, a lot of disorganized convection. In this case however, we have a 50kt speed max associated with our mid-level "kicker" that's going to lead to stronger deep-layer shear atop our Summer instability. Steep lapse rates overlapping a very moist & unstable boundary layer with plenty of effective shear sets the stage for more organized severe storms. While not impossible to see this type of setup at all, it's also not the most common thing during late-June.

GOES East water vapor imagery shows an upper-low over Wyoming with an embedded shortwave trough pivoting around it. This shortwave will eject over the central plains tomorrow with a 50kts speed max overspreading the KS/OK/NE region. Surface cyclogenesis will occur and surface-low will deepen and lift northward, bringing a frontal boundary with it. 

A "theta-e" axis associated with out moist sector will be established across the target area providing plenty of "juice" to work with. 

A plume of very steep lapse rates atop a very moist boundary-layer will aid in strong instability developing tomorrow afternoon. Effective wind shear of 40kts and backed surface winds, especially along the boundary, may support supercells and decent curvature of low-level hodos suggests tornadoes are possible. Low-level thermodynamics also seen seem to support the stretching of low-level circulations to the ground, should they develop. 

Storm-relative helicity values support rotating updrafts, particularly after 0z (7pm) when the low-level jet gets cranking. 

There are uncertainties regarding the exact evolution of tonight's convection as well as location of outflow boundaries tomorrow. The NAM has also been a well-noted consistent outlier. We'll tighten up the details tonight and in the morning at the hotel so stay tuned for that. It looks like a busy day tomorrow though. Severe chances, though not as substantial as Sunday, will continue through Tuesday and I'll have chase forecasts for those days as well following tomorrow's chase. See ya soon!

Chasing Severe Storms in Missouri & Arkansas

Good morning! I've got to be brief today because I'm already in Missouri and I'm westbound to position for severe weather in the next couple of hours. The target is along the AR/MO border in western MO where I think a low-end tornado threat is coming together. I personally suspect an increase of severe probs from the SPC but we'll see.


So the setup today is very similar to what we saw Thursday (which did produce a brief, but photogenic tornado near Cape Girardeau, MO). It's been yet another tricky forecast with another overnight MCS blasting through the target area during the morning. That said, the atmosphere seems to be recovering well, no doubt aided by deep, tropical moisture, dew points ~70ºF+. Temperatures are in the mid 80's already as well and this has helped increase the degree of destabilization despite convective cloud cover. A semi split-flow jet stream regime is in place and ridging locked in across the area has resulted in strong heating. A speed-max upstream appears to be timed out favorably to cross over southern NO by this evening.
Today's chase really lies in the details though, particularly on the mesoscale. Fairly steep lapse rates (8ºC/km+) associated with the EML are located across OK/KS and as our speed max enters the nose of the southern stream ridge it will spread this plume of steeper lapse rates atop the moist sector, which we already mentioned is very moist and quickly destabilizing.

The real kicker today is the position of a major outflow boundary laid down from the early-period MCS, and other more subtle boundaries as well. Morning surface analysis showed this boundary was located just West of Springfield, MO extending NE/SW. I expect this will serve as the trigger for convective initiation within the next 1-3hrs. Any storms that develop will likely be severe and capable of damaging winds and large hail, given steep lapse rates (low-level and aloft), a well-mixed boundary-layer, and large MUCAPE (4000-5000j/kg) including sufficient CAPE above the -10ºC layer.

Like I said, I think the greatest risk is along and South of I44 to Little Rock, AR. Morning observed soundings showed a strong cap in place but that's been eroding throughout the day due to both cooling aloft and heating below it. A "loaded gun" thermodynamic profile with a somewhat curved hodograph suggests strong rotating updrafts may be supported. Although the tornado threat is low, it's still realistic.
Good luck to others out here today, I think there's one clear target so it should be fun in the jungle.