2013-05-18 FCST: TX/OK/KS/NE

[Jeff Duda]

This looks like cap city to me from NE through OK, unless you're right on the dryline, at which point lapse rates are very good, but moisture depth is pitiful. It may be possible for a storm to form on the dryline and move out into the warm sector where CAPE and CIN are both greater. If the storm is well established with a very strong updraft, it may be able to survive the 50-100 J/kg of CIN that will be present and make for a nice looking supercell. I'd be surprised if there were more than one or two tornadoes out of this, although areas right along the boundary do show more than sufficient low-level shear for tornado production. However, these are still areas with either super steep lapse rates and no moisture or areas with a fairly strong cap.

 

[Derek Weston]

NAM has been breaking out precip on this day consistently despite some of the cap concerns. SPC doesn't seem to think NEB on north will have much of a cap issue. Latest NAM puts some big parameters over NEB. May end up with a linear even up there eventually, but, I'm more than willing to take a chance.

It's a Saturday in May with big CAPE and some good shear. See you all on I-80.

 

[Derek Weston]

Last few NAM runs have been showing huge parameters and precip across W KS into SW Neb. SPC just went mod for this area. Could be a very fun day. One of my concerns is that we may have weakish anvil level winds and storms may be a bit rainy... nevertheless, still quite a bit of potential. Really encouraged by the placement of some stronger 500 flow over this region though, rather limited area, but it's there.

EHI values are just huge across this region by 21z. Anything that realizes the environment painted by the 12z 5/17 NAM could be a monster.

 

[Kelly Sugden]

Starting to focus in on between highway 283 and 183 across SW Kansas. Low level shear looks excellent and could lead to enhanced non hydrostatic vertical pressure gradient forces (enhanced updraft) if a storm can sustain itself within said region.

 

[Marcus Diaz]

The soundings along whole dryline look like they have backed-veered-backed wind profiles. The exception would be in SW NE or down into OK where the dryline mixes out badly. Just wondering if anyone knows of good supercells with this sort of wind profile? In my head I would think it didn't matter since it would just shove the anvil more north but I can see it affecting the updraft and the way it rotates with height. I'm not too keen on the ins and outs with soundings, so trying to get some insight.

 

[John Farley]

The back-veer-back profile is still there somewhat in tonight's 0Z NAM run, but it does seem to become somewhat less of an issue by 0Z tomorrow evening than during the afternoon. Another thing that concerns me a little for my target in southwest KS is that there is not too much veering with height in the wind below 850 mb - it is pretty much southeast from 850 down - would like to see a little more directional shear in the lower levels. But that said, the deep layer shear is quite good by 0Z, and the CAPE is explosive. Once again the NAM breaks out plenty of precip in SW-SC Kansas by 0Z, so I am thinking that one or two big-time supercells are a good bet in that area. Check out Mike Umscheid's excellent DDC forecast discussion, including his reasoning on how the lower-level jet could, unfortunately, lead to a strong tornado or two after dark. But even if there are not daytime tornadoes, I think the chance for an impressive supercell or two is very good, and a tornado before sunset is not out of the question with such explosive instability and improving deep-layer shear by 0Z.

 

[CGardner]

Yeah, after reviewing the NAM and SREF. I think it will be capped till late (00-01z), and then some isolated monsters popping up from south-central to sw KS. The shear and helicity are spotty at best, but the energy and moisture is there. As for John, I agree about the veering, but the winds from surface to 850 are 10-15 knots difference, so stretching can come into play. Which, I'm taking my chances on the middle ground and taking the same route as Derek and hitting the warm front advection in north-central KS.

 

[Greg Blumberg]

A little late night thoughts from looking at some current observations and the day 2 SPC outlook issued previously. It's not looking like overnight convection will happen tonight (as mentioned in the SPC outlook), given that most of the warm air advection is at or below 850 mb, where it will be difficult to lift parcels up to the LFCs. There is simply too much CIN that these parcels would have to overcome, especially if you look at different soundings like the 00 UTC OUN, LMN, and FWD. Fortunately, I'm hoping that the ascent forced by the warm air advection across Oklahoma will help cool the layer beneath the cap more than expected (as the inversion really begins above 850 mb), which could allow for an earlier initiation time.

Both the 00 UTC NAM and GFS look alright. I like the NAM's solution best if we're looking at a nice chase near Wichita. The 00 UTC forecast sounding for that area looks quite ideal. The GFS however is showing some rather odd boundary layer evolution and the advection of a 500 mb cloud deck throughout the day. I'm very skeptical about how both of these models handle the boundary layer evolution over time, so I'm very hesitant to buy into either one of them right now. I am curious though to see what the storm-scale models will be suggesting for tomorrow.

 

[Bill Hark]

Veryimpressive chase day possible for Saturday. The 500 mb winds should be weak butsufficient at 30-40 from the SW through western Kansas and Nebraska per the 00ZNam as a trough approaches. Storm motions will be fairly slow. I like theforecast SE surface winds due to a NAM forecast low over the OK panhandle (abit to the north per GFS). Dewpoints will be up to 70 ahead of a dryline with ahint of a dryline punch in SW Kansas with 4500 forecast CAPE in a bullseye abit to the north and forecasat SRH increasing to 150-200 by 00Z. I also reallylike the increasing SW 850 mb winds by 00Z. I am worried about the cap for thesouthern target but the NAM does break out precip in that area while the GFSshows only to the KS-NE border by 00Z and further south after dark. As of now, my southern target would be GardenCity for very late storms. There may beadditional opportunities near the KS-NE border and possibly SD. Hedging my forecast by starting on I-70 andreexamining the updated forecast models mainly for forecast precip development. Bill Hark

 

[Robert S. Thompson]

Agree with other recent comments. We are starting off in the Nebraska panhandle due to chasing yesterday's convection. Probably going to target west-central KS. The stratus up here in NE may be too limiting. RST

 

[samuel stone]

In Hutchinson right now about to move west toward the larned area so I can play north or south of there. I really like the prospects of discrete supercells to form on the dryline from south of beaver Oklahoma to ddc and move NNE into better lcls CAPE and LL shear. I figure for the first hour and a half or so storms may struggle to produce tornadoes but after 0z I think a late-evening nuclear supercell or two could be very dangerous anywhere from alva to greatbend.

 

[Mike Smith]

I'm heading for PTT and leaving around 12:30. I have a complete forecast discussion here: http://meteorologicalmusings.blogspot.com/2013/05/my-personal-storm-analysis.htmlAt 16Z there is already an 0-1km EHI value of 4 (!) just SE of DDC. The surface low is near GUY with a leftover boundary (quasi-warm front) from the low to Edmond. I believe tornadic supercells will fire on the dry line 3-4pm. My very preliminary target is Protection, KS. HOWEVER, I will be stopping at PTT to evaluate the chance of something firing under the difluent zone near PTT in the extreme instability with decent helicity. the 16Z surface CAPE is already 5,000+j (!) in west central OK. Two thoughts: This is an easy situation where you could get cut-off...be extra careful.Second: Stop in Greensburg to buy gas, snacks, food. If you are staying in southern KS overnight, consider their very nice and new Best Western. Support the town's recovery.

 

[Brian McKibben]

The SPC 4km WRF has convection firing on the DL in Ok and then getting all the way to central OK by 01Z. If this is true, it could become an interesting day for OKC metro.

http://www.emc.ncep.noaa.gov/mmb/mpyle/spcprod/12/

 

[Mike Johnston]

Just looking at current observations and what the RAP model is showing over the next few hours, looks like a subtle wind shift line is setting up, roughly from Woodward, OK to Kinsley, KS. With all the extreme instability building over the area, something like this may provide a point of surface convergence to initiate the storms out ahead of the dryline itself.