jojo762

Oops. Forgot to check SFC obs in a while to see where the front was, given that we have a crashing CF today. Tornado potential is pretty much NIL in that case, storm is elevated.

Supercell in Wise Co./ moving into Denton Co TX/ needs attention... Exhibiting some low-level rotation, and its moving into a populated area. Appears that it actually has two areas of rotation.

Wind-profile highly favors supercell structures... But low-level winds are fairly weak speed-wise, resulting in 0-1KM SRH that just isn't quite good enough, per 00Z FWD sounding. Believe the cap may be playing some role in limiting tornadogenesis as well.

...A TORNADO WARNING REMAINS IN EFFECT UNTIL 745 PM CDT FOR SOUTHEASTERN COOKE COUNTY... At 721 PM CDT, a confirmed tornado was located near Gainesville, moving east at 30 mph. The confirmed tornado is located just west of Interstate 35 between Valley View and Gainesville. HAZARD...Damaging tornado and golf ball size hail. SOURCE...Weather spotters confirmed tornado. IMPACT...Flying debris will be dangerous to those caught without shelter. Mobile homes will be damaged or destroyed. Damage to roofs, windows, and vehicles will occur. Tree damage is likely. This tornado will be near... Lake Kiowa around 735 PM CDT. Other locations impacted by this tornadic thunderstorm include Valley View.

BULLETIN - EAS ACTIVATION REQUESTED Tornado Warning National Weather Service Norman OK 522 PM CDT FRI APR 21 2017 The National Weather Service in Norman has issued a * Tornado Warning for... Southwestern Johnston County in southeastern Oklahoma... * Until 545 PM CDT * At 522 PM CDT, a severe thunderstorm capable of producing a tornado was located near Ravia, moving east at 25 mph. HAZARD...Tornado and golf ball size hail. SOURCE...Radar indicated rotation. IMPACT...Flying debris will be dangerous to those caught without shelter. Mobile homes will be damaged or destroyed. Damage to roofs, windows, and vehicles will occur. Tree damage is likely. * Locations impacted include... Tishomingo, Ravia and Milburn. PRECAUTIONARY/PREPAREDNESS ACTIONS... TAKE COVER NOW! Move to a storm shelter, safe room or an interior room on the lowest floor of a sturdy building. Avoid windows. If you are outdoors, in a mobile home, or in a vehicle, move to the closest substantial shelter and protect yourself from flying debris. && LAT...LON 3422 9684 3431 9682 3431 9653 3416 9654 TIME...MOT...LOC 2222Z 277DEG 20KT 3426 9677 TORNADO...RADAR INDICATED HAIL...1.75IN

Bret Hendrickson has a good view of a large wall cloud on http://www.severestudios.com/livechase/ EDIT: Well he did... Chasing in SE OK is a pain.

That Johnston Co. Oklahoma supercell is definitely becoming better organized. Presentation improving on both radar and chaser streams.

TOR watch out for NE TX/SE OK/W AR until 1 am... 50/20 probs.

Cell firing just north of Ardmore could be one to watch...

Mesoscale Discussion 0538 NWS Storm Prediction Center Norman OK 0309 PM CDT Fri Apr 21 2017 Areas affected...Southern OK...North TX...Southwest AR...Far Northwest LA Concerning...Severe potential...Watch likely Valid 212009Z - 212215Z Probability of Watch Issuance...80 percent SUMMARY...Severe thunderstorm development is expected later this afternoon. Very large hail, locally damaging winds, and a few tornadoes will be possible. Watch issuance is anticipated in the next 1-2 hours. DISCUSSION...At 20Z, an outflow-reinforced frontal boundary has become nearly stationary across north TX, southeast OK, and southern AR. Visible imagery indicates slowly deepening cumulus along and south of the boundary, though wave features noted in the cloud field are indicative that some convective inhibition remains. Ongoing elevated convection across central OK is being supported by ascent associated with a rather strong but low-amplitude midlevel shortwave moving into southwest KS. This ascent will likely only glance the region along and south of the boundary, but, in conjunction with continued boundary-layer heating, will help to support convective initiation later this afternoon into the early evening as the remaining CINH is eroded. Along and south of the boundary, steep midlevel lapse rates atop a warm/moist boundary layer are supporting moderate-to-strong buoyancy, with MLCAPE of 1500-2500 J/kg noted in recent mesoanalyses. Effective shear of 45-55 kts is more than sufficient for organized storm structures, with initial discrete supercell development expected before consolidation into more of a linear mode along the boundary becomes more likely into the evening. Any discrete supercell that develops in the warm sector will be capable of all severe hazards. The tornado threat will be maximized with any supercells that interact with the frontal boundary, especially in areas where some heating/recovery has occurred north of the boundary. While the timing of deep convective development remains somewhat uncertain, tornado watch issuance is likely when initiation appears imminent, which will likely be sometime in the 2030-22Z timeframe. ..Dean/Goss.. 04/21/2017

SPC still seems concerned about the potential of a strong tornado, albeit the potential is highly conditional.

We were, but that's the nature of Mid/Long-range forecasting... Focusing on the pattern is what's important. We had a big-league trough ejecting into the plains with what the models showed as good moisture return (didn't pan out with the moisture and trough orientation/location). Next week we have several potentially potent shortwaves being progged, with solid moisture return being shown by mid/late week. Which generally lends confidence in increasing chances for severe storms.

Yep... you can use http://kamala.cod.edu/SPC/ when this happens. It doesn't have as many features for the maps as SPC does, but it gets the job done, and usually updates faster than the actual SPC page.

Probably not... But there are so many things going against it, most notably the crashing front and the possibility of widespread precip (which will also effect northward extent of the warm front)... Still expect at least a couple tornadic supercells on Friday in S OK/N TX.

Think my attention is starting to turn to late next week. Both the GEFS and EPS generally agree on showing a substantial trough or two across the central united states in the 4/26-28 time-frame.

Mesoscale Discussion 0519 NWS Storm Prediction Center Norman OK 0229 PM CDT Wed Apr 19 2017 Areas affected...Parts of sern NE...swrn IA...nwrn MO...n cntrl/nern KS Concerning...Severe potential...Watch likely Valid 191929Z - 192200Z Probability of Watch Issuance...95 percent SUMMARY...Thunderstorm development with increasing severe weather potential is expected by late afternoon. At least a couple of severe weather watches are likely to be issued across the region by 21Z. DISCUSSION...A cyclonic mid/upper jet streak (including 50+ kt at 500 mb) is in the process of nosing through the central Plains and mid Missouri Valley region. Strongest forcing for ascent in the exit region of this feature likely will remain focused well to the cool side of a fairly sharp surface frontal zone, along which a modest surface cyclone is now beginning to migrate east northeast of the central Nebraska/Kansas border area. At the same time, the nose of a plume of warm and capping elevated mixed layer air is wrapping into the mid Missouri Valley region, across much of the warm/moist sector of the surface low, and northward to the cool side of the front ahead of the low. However, latest model output, including the Rapid Refresh, suggests that the leading edge of lower/mid tropospheric cooling is now roughly near/east of the Grand Island NE through Russell KS. As this continues to spread east northeastward this afternoon, guidance indicates that it may provide the focus for increasing thunderstorm development by 21-23Z, from near the surface low southward along the dryline (as it is overtaken by the southward advancing cold front) into parts of central Kansas. In the presence of thermodynamic profiles characterized by very steep mid-level lapse rates and mixed layer CAPE on the order of 1500-2000 J/kg, deep layer shear appears more than sufficient for supercells. Near a 40 kt southerly 850 mb jet, sizable clockwise curved low-level hodographs will contribute to a risk for tornadoes. The extent of the tornado threat remains a bit uncertain due to an expected tendency for fairly deep boundary layer mixing and some drying within the warm sector, and rather cool/stable air to the north of the front. Any tornadic potential may tend to be maximized within a rather narrow corridor along and to the north of the warm front, just ahead of the surface low, across parts of southeastern Nebraska into southwestern Iowa. ..Kerr/Thompson.. 04/19/2017

Low-level VWP at KOAX is pretty nasty. Winds at 2KFT are east-southeast at 20kts, and winds at 9KFT are southwesterly at 50kts, creating a nearly 90-degree angle and a whole lot of directional and speed shear. Not entirely sure since the wind profile isn't complete so the SRH won't show on the VWP hodographs, but believe 0-3km SRH is currently 300-400+ m2/s2 at OAX, which is obviously favorable for tornadoes... Doubt it will change too much by CI as the warm front should remain in the general vicinity.

Nope. I live near Wichita so this isn't really in my neck of the woods. Wouldn't mind driving up to Salina though to see if anything discrete fires up near there, but I don't think its worth it today. Anyways, almost all the CAMs seem in good agreement on several discrete/semi-discrete supercells going up in SE NE/W IA within the 10% TOR by 21-22Z, so things could get interesting later on along the warm front.

Shifted the 10% TOR a tad further west at 1630Z. Latest HRRR runs seems to support a longer-duration of discrete/semi-discrete activity, so we'll see if we can get anything out of today.

12Z GFS continues to maintain a significant severe risk from south-central OK southward into northern TX.... current indications from the GFS are for MLCAPE values of 2000-2800J/KG, 0-6KM shear of 60-70kts, and 0-1KM SRH on the order of 300-400m2/s2 across the main threat area by 00Z.

00Z GFS trended a tad further north with the warm front, yet again, and shows an environment conducive to supercells capable of all severe-hazards from south-central Oklahoma southward into north-central Texas. Now within 100 hours of the event, and model variability continues to be prevalent...

Seems like most GEFS members certainly have been keening in on some sort of big-time trough(s) entering the plains sometime in the late April-early may time. Haven't had a Synoptically-obvious big-time severe threat in the plains, that actually turned out to be big, in what seems like forever. Have had several "big" days in recent years, but none were really expected to be as big as they were. 4/14/12 was the last plains tornado-driven high risk, maybe we can change that in the next month and a half...

Certainly is. Have to believe there is at least some potential for multiple days of severe weather during that time frame, perhaps a shot at a big-league day with the final (intense) trough. Notable that this trough on Friday still has a decent amount of potential given its strength, just a few things going against it right now. 18Z GFS was interesting.

Models still generally support severe weather somewhere across the southern plains on Friday. The extent of and location of any potential higher-end threats beyond a slight risk is still TBD.

Appears that the Comanche County supercell is weakening rapidly.