2012-03-19 FCST: TX/OK/KS/MO/AR

[cstrunk]

New SPC Day 1 outlook includes a Moderate risk area from central TX to extreme southeast OK. Multi-mode severe weather outbreak appears likely over a large region, including supercells and tornadoes.

Leftover (possibly severe) convection from tonight's dryline action will be moving northeast across central/north TX into OK. The evolution of this convection will be key to the amount of instability that can take place, particularly the farther north you go. NAM/GFS models are indicating up to 2000 J/kg CAPE from north-central TX south. Higher instability is likely into south TX around San Antonio. Shear looks strong at 50-60 kts, up to 70 kts in north central TX and into OK.

At this point, I'm having a hard time picking a target area. I have a couple friends that will be joining me for their first chase, and we will be leaving Tyler, TX hopefully by noon. It's going to depend on morning observations and trends for me. If it wasn't quite as far away, I would head down towards San Antonio. A few monster supercells should form west of there later in the afternoon into the early evening. We'll most likely stage south of Dallas on I-35 somewhere and go from there. It's also possible that the DFW area and just to the north might be a possible target. The 00z 4.0 km WRF-NMM simulated reflectivity for tomorrow indicates there might be some supercells in this area in the afternoon after the first wave of convection passes.

It's a really complicated forecast, and I'm not that good at forecasting. I would love to hear opinions from other chasers!

 

[cstrunk]

A moderate risk in Texas and no one else has any comments?

The large MCS/squall line in west TX has not propagated east very far overnight. As it moves farther east I expect it to intensify and think there will be the possibility of tornadoes within the line as it moves east/northeast across north Texas/southern Oklahoma. Shear is very strong across north Texas, with 60-70 kt bulk shear and 0-1 km SRH approaching 500 m^2/s^2 along the Red River Valley. I would watch out for anything that can fire ahead of the squall line in North Texas through the afternoon hours.

As the first round of convection clears the area, models are depicting another round of convection - likely more isolated/supercellular in nature - firing from southwest of DFW to west of San Antonio later in the afternoon. Other storms may fire east of this farther into the warm sector. Parameters are very high across all of the moderate risk area this afternoon and evening. I expect to see some monster storms.

I'm still planning on leaving Tyler by noon and will be heading towards an area southwest of DFW. I'm hoping the convection south of DFW will be more isolated in nature - moreso than farther north.

 

[Jeff Snyder]

It looks a little bleak from my vantage point in Gainesville. I waffled heavily on whether or not to chase today -- it looks quite marginal. There is strong low-level shear courtesy of a strong low-level jet (40-60 kts @ 850 mb) from eastern OK southward to the east of the slowly-advancing outflow boundary. Some diurnal heating has occurred in the warm sector courtesy of some broken cloud cover, which has lead to moderate instability (CAPE) in this area. However, above the strong low-level flow is backed flow of similar intensity. You can see indications of this in a loop of vis sat data -- note how the anvils are streaming northward relative to the storms. Thus far, even though the OFB isn't advancing very quickly (~20 kts?), storm motion has largely been rearward relative to the OFB. As such, we haven't yet been able to get a storm in the warm sector out ahead of the OFB. There is one intense storm W of Fort Worth at this time, but it too is behind the OFB (you can see this in radial velocity data). Can it turn to the right enough to give it a storm motion that would move it away from the OFB? Not sure that'll happen.One other issue is that model analyses and forecasts are showing relatively weak vertical wind shear through the cloud-bearing layer. Partly as a result of the very strong low-level flow, shear from 850 mb to 300 mb isn't impressive, by any means. So, any supercell that may be able to get going in the warm sector may have issues with organization. The 12z NAM also shows some S-shaped hodographs in the warm sector as a result of weakening flow above the low-level wind speed max near 850 mb. Not optimistic.

 

[cstrunk]

You're right, Jeff. Looks like a huge bust. The models did not seem to handle this one well at all. I thought we'd see something blow up in the warm sector, doesn't look likely now.

 

[brice.coffer]

The 800mb elevated mix layer won out today in the warm sector. I did the same thing as Jeff. I started the day heading south from Norman to Denton, then chased a storm towards the Red River and into Oklahoma before calling it quits. West of Sanger, TX it briefly evolved into an elevated supercell. Decent mid-level rotation allowed for a hail core to develop with a couple pixels of 70+ dBZ on the lowest tilt.

Pretty crap day but I started to look through my pictures from yesterday on the way home. Hopefully I'll post those later tonight or tomorrow.

 

[STexan]

It's too bad, too. The system(s) were slow moving and would have been a videographers and photographers dream chase setup in a great chase region. I zig-zaged up and down between Sanger and Gainesville and Decatur and Sherman staying ahead of the frontal zone as it crawled eastward. Looked somewhat promising in a few places briefly but nothing. Not even a lot of lightning activity that would have been worth setting up for. Next time, perhaps.