2017-10-21 EVENT: TX/OK/KS/MO/IA

[Jonathan Beeson]

An interesting setup appears to be in store for tomorrow, as a pretty sharp but diffused out trough ejects into the Plains. Tornado potential doesn't look to be the greatest, and any supercells that do form could turn messy quickly. However, it's worth a watch considering it may be the last appreciable Plains threat for quite some time as the cool season climatology will soon be kicking in and shifting most of the significant severe weather potential into the Mississippi Valley and points eastward.

A fairly substantial trough will be kicking into the central U.S tomorrow, with a very strong 989mb surface low over southern Canada. However, deep layer shear seems like it will be lacking a bit, which is something that doesn't often happen with the often times more kinematically driven cool-season events. Also, proximity to the surface low will be another limiting factor as this thing is way up in Canada. Not exactly an optimal position for a southern plains event. I wouldn't completely rule out a secondary low forming somewhere in W Oklahoma, but I'm not exactly high on those prospects either. If one does form, it would likely locally increase the low level shear and associated tornado potential in SW Oklahoma, but I'm not getting too high on that as I mentioned.

There will be plenty of thermodynamics to work with, especially being late October. However, any discrete cells that can get going along the dryline will be undercut by a rapidly crashing cold front that will encourage linear growth very quickly. This will likely be a case where chasable tornadoes are most likely within a couple hours of initiation before things turn messy and upscale.

Being in Dixie, I won't be out there as I'll be balancing between armchair chasing and college football. However, if I were to make a play tomorrow, I'd target Lawton and hope that a supercell can get going on the dryline for a little while before the cold front crashes in and forces things linear.

 

[Drew Terril]

RIght now, it appears that a secondary low will form in the TX Panhandle and work it's way into the SW OK/NW TX area. There's still some disagreement among models. NAM and NAM3km favor the low traveling along the Red River, and the GFS favor it staying closer to the I-40 corridor. Either way, it appears that somewhere between Lawton and Wichita Falls will be the ideal place to set up.

That far east, I'd tend to stay on the south side of the river, as it's easier to push north and east across the river (either via I-44 or OK/TX-79) than it is to go south to catch up to a storm. My preliminary target will be Wichita Falls, TX, but early and mid morning runs may force me to adjust.

I don't anticipate there being more than a 2-3 hour window for discreet supercells, and if I didn't live within 200 miles, I probably wouldn't pounce on it. That said, I'm under 150 miles, and I'm off work, so I'll be out.