Quincy

Watching the pronounced outflow boundary in far Northwest Texas. It’s slowing down and resides in an environment characterized by 4000+ J/kg MLCAPE, 30+ kt bulk shear and enhanced surface vorticity. Low level CAPE is currently modest, but should improve through the afternoon. CAMs struggled with evolution of early day convection across Oklahoma, but taking a consensus and adjusting for current obs, suggests convective initiation will be possible by 22-00z, somewhere around the Northwest Texas vicinity. (Possibly far southwestern Oklahoma or maybe the southeastern Texas panhandle) Today could end up being another mesoscale day like yesterday.

Yesterday featured a hail storm around parts of Denver and a tornado in Midland, TX. I extended the thread through June 4th, as the active pattern looks to continue for a few more days, before a ridge builds in the West. That will probably mean a relative lull in severe action for a while, aside from local mesoscale events.

Marathon, TX got smacked by the hail core. It looks like large amounts of small to marginally severe hail fell. There were several inches accumulated in town: It looks like a notable MCS may plow through parts of Oklahoma and Texas tomorrow, with additional supercell development possible to the west, on the High Plains.

Just finished chasing the supercell down by Marathon, TX. It produced a couple of landspouts. A little Fort Stockton area magic, I suppose.

Yes, the hail core went right through Pettit, which is a near ghost town about 7 miles NE of Whiteface. I went back up there and saw tennis to baseball sized hail all over the ground. Granted, it had about 45 minutes to melt… By the way, the picture I took was from an earlier supercell. The second one was a direct hit. A third one also grazed the area, but it was noticeably weaker. That area really got pounded. Lots of flash flooding due to heavy rain and hailmelt.

Saw this supercell near Pettit, TX earlier. Still out here chasing for a while longer.

It hit Abeline before I left there this morning. Guessing we had gusts up around 40-50 mph

This could be a focus across West Texas later on as well. It’s looking like another busy day around the state.

Friends out near Tyler took shelter, had a tornado warned cluster earlier with hail as well. Not exactly the wake up call you’d want. I know it’s early, but this whole complex could grow upscale and impact the greater Houston area later on…

Chased the supercell near Van Buren, MO today that prompted a PDS tornado warning. It’s just about one of the worst places to try to storm chase, I didn’t see anything conclusive, but it was definitely an HP beast.

Moderate Risk upgrade incoming…

18z subjective surface analysis: Isolated convection should first occur near a low and warm front from far northeastern Oklahoma into southwestern Missouri this afternoon. CAMs show isolated to scattered supercells across southern Missouri by late afternoon. I do wonder how far north the outflow boundary draped across northern Arkansas will retreat, as that could locally enhance the tornado threat. SPC has a 10% hatched (sig) tornado area outlined from northeastern Arkansas into far southeastern Missouri. CAMs have steadily trended south with this feature, when compared to earlier morning runs. There’s also a question about how far east storms may initiate, given weaker forcing and proximity to the fresher outflow from the Ohio Valley MCS. Either way, there’s a conditional tornado threat near the outflow boundary and maybe near a quasi triple point, around the AR/MO/OK border area. Considering this area had tornado damage last night, that’s also unnerving.

Overturned environment. Big blob of meager low level lapse rates.

Not sure I’d say total bust, but the CAMs were clueless with the early arc of storms across SW Oklahoma. The lack of capping was detrimental here. I do find it interesting how Nadocast did fairly well and the analogs were mostly garbage too. (They generally favored Kansas for the biggest tornado threat) One of the stranger evolutions I can recall for a potential higher end day.

A dud for central Oklahoma, thankfully. I think early storm initiation and all of the left moving cells leading to clustering really tempered the event across KS/OK. North Texas had a few notable tornadoes and what about that discrete cell by Ardmore? I called the chase off an hour ago, a whole lot of nothing.

90/80 probabilities (2+ tornadoes, 1+ significant tornado) for the PDS Tornado Watch. Summary says hail up to 5” in diameter is possible.

Incoming PDS Tornado Watch for portions of the Southern Plains. Most high res models are doing a very poor job with moisture return over Oklahoma. HRRR has dews dropping, where they’re continuing to steadily increase. With that said, the 18z NAM shows numerous supercells up and down the dryline by 5-6 PM with 19z HRRR trending in that direction. Adjust for erroneously low dew points and the NAM solution seems plausible, if not likely. It could be a very ugly evening.

18z surface analysis, along with an auto updating map for Oklahoma dew point trends: Warm front is moving quick and it’s movement north and will be a key factor with influencing significant severe potential from northern Oklahoma into southern Kansas.

What a shift in 24 hours. Last night, models struggled to convect anything in OK/TX Saturday night. Now there is a very aggressive middle signal across the board. It’s odd seeing the HRRR be the most aggressive, but this is not a typical parameter space. One key difference between tomorrow and May 6th (last high risk) is that we can expect a more westerly component to the deep shear vector. Even if there is convection up and down the dryline, the wind profile alone will strongly favor a supercell storm mode.

Using the HREF mean as a benchmark, if shows 12hr (12z Sat-00z Sun) neutral or slightly rising heights from the Red River, southward. Subtle negative height tendencies are noted from NW Oklahoma into western Kansas, but more substantial height falls are not progged to arrive until overnight The CAPE/shear overlap is certainly conditionally favorable for significant severe. Convective temperatures on the HRRR are close to being reached by 00z Sunday. The 3km NAM shows isolated CI with multiple areas of attempted CI. SREF probabilities are a bit tame too. Given a robust jetmax ejecting into the Plains by 00z, it’s hard to imagine there isn’t at least isolated CI. Even if more widespread convection is delayed until evening, the environment only gets more volatile before there is some notable increase in CINH, after midnight. SPC’s new Day 2 outlook includes a small hatched sig tor area over NW Oklahoma. Given model trends, you could see the most significant tornado threat possibly get nudged back into SW Kansas, with timing centered around early evening, but we’ll see. We also need to get through Friday first…

Recapping tonight’s dusty tornado in southwestern Oklahoma with a few images. These were taken in Eldorado.

Chasing the sig tor in SW Oklahoma

With regards to the Southern Plains severe threat today: Focus is along the dryline, although there are mixed signals about storm coverage and longevity. Large scale forcing is modest, over the NW Oklahoma/Kansas portion of the region, but height falls will be somewhat more than areas to the south, where deep layer flow will be stronger. Midday convection across North Texas complicates the forecast to some degree. The western flank may be a focus for intense high precipitation supercell development later. The middle area, SW Oklahoma into NW Texas may be where the best overlap of ingredients exists. This is where there seems to be the most model agreement, although augmentation of the environment due to downstream convection cannot be overlooked. Over western Kansas, there may be a relative minimum in convective coverage. CAMs are mostly void of convection, although a few NAM/WRF members and occasional HRRR runs suggest at isolated convective initiation, somewhere near Dodge City, perhaps near where an effective warm front intersects the dryline.

Mean troughing across the Northwest will allow several disturbances to rotate around its base over the next few days. Expecte severe threats to continue into the weekend from the Plains into parts of the Midwest/Mid-South. Today: A sagging cold front, convectively reinforced across Oklahoma and vicinity as of midday, will be the focus for severe thunderstorm activity today. Elevated supercells across central Oklahoma earlier this morning will pose the initial severe threat from southeastern Oklahoma into Arkansas. The environment south of the front, across much of Texas toward the Arklatex, is already strongly to extremely unstable. With forcing ahead of the cold front impinging on rich low level moisture in place, widespread convective initiation is likely by early afternoon. Although deep layer shear is more than sufficient for organized severe convection, wind profiles suggest mixed storm modes with numerous cell interactions. A few initial supercells are probable across central Texas, SW toward the Rio Grande, but even these storms should tend to grow upscale fairly quickly. Thursday: Moisture recovery may take a while due to convective overturning from today/tonight. The most likely area for widespread convection during the afternoon will be across the Dakotas into Nebraska, as an upper level disturbance ejects out of the Northern Rockies. A more conditional severe risk may evolve near a dryline from Kansas, southward into western Oklahoma and west-central Texas. Models vary with convective coverage, but at least isolated convective initiation seems possible. As a cold front surges southeast Thursday night, it should overtake the dryline in Kansas and shunt appreciable low level moisture south across the Southern Plains. Friday: A shortwave is progged to eject from the Central Plains toward the Middle Mississippi Valley. This combined with the surging cold front should push the severe threat into parts of the Midwest, southward toward the Arkansas vicinity. Some severe thunderstorms may once again impact parts of Texas, but with several days of convective overturning and moisture getting pushed south, the threat may be limited.

Quick surface analysis: Modifying outflow/moisture gradient over Iowa may locally enhance the tornado threat. Supercells already initiating near the deepening surface low. Expect an expansive, broken line of supercells from Iowa, down into Missouri and southeastern Kansas within the next 3-4 hours. Isolated development is possible into northeastern Oklahoma, but also near a trough-like feature ahead of a cold front. Some CAMs show isolated development in the warm sector, here, from southeastern Oklahoma into Arkansas and southern Missouri. Not pictured above, but there’s also isolated supercell potential in North Texas later on. Multiple areas to watch. It looks like a regional severe outbreak is likely, especially across Missouri and Iowa. We’ll see how far NE it spreads. I’ll be hanging back around the KS/MO/OK border area, where more isolated activity is expected, along with storm motions that are not as fast. 50-60 mph storm motions are likely across Iowa and vicinity, but perhaps closer to 35-45 MPH on the SW trailing end of supercells.