2014-06-01 FCST: NE/KS/CO/SD/WY/OK/TX/NM

[Bob Schafer]

The mods will have to decide how to fix this thread, because based on this morning's 12Z GFS there are legitimate potential targets all over the place. It's insane.

1) DL from E NM to SE CO, into N and S of the OK PH, under the upper jet nose.
2) E WY into NE PH and N'wd into MT, where upslope flow and Td's as high as lower 60's (ºF) resides under light but diverging upper winds in the left-exit region.
3) WF from SD into MN. This region features small hodos, backing winds at H4, and big moisture, so bring your umbrella and raincoat.
4) My fav target of the bunch: NC KS into extreme SC NE, E of the sfc L. The 996mb sfc L centered over the corner of CO/KS/NE promises screaming inflow there with CAPE ~2000. The fSounding suggests a bit of an inverted V, but the LCL's look acceptable. The upper support could be better, but it's... ok.

140602 06Z prog advertises 6-hour rainfall for all 4 potargs. (Potential targets, hahahaha...) ...but just a little for "potarg 1)" where 700mb T's are into the 15ºC+ range.

You'll be lucky if you get anything higher than 30kt bulk shear anywhere, but at this point of this season we take what crumbs we can get.

 

[Royce Sheibal]

I've been considering Sunday the 1st for a couple days now, GFS looks pretty favorable for the Nebraska target. There's even a little bit of PVA going on, which is always a bonus. However, every model that goes by seems to push the target further and further NW into the no-mans near the sandhills, and the further NW it goes the more I worry about high based and capping issues. I might save my gas money and try to stay local for Tuesday the 3rd instead.

 

[Jeff House]

June Boom

Sunday should be an excellent chase day. Several states in play including SD/NE//KS/WY/CO. Euro is about a state south of GFS on the whole setup, but it looks like a gem on either model. Surface low should be in the High Plains with a warn front (WF) extending east. A dry line (DL) or at least lee trough will extend south from low. Upstairs jet stream winds will be okay - not great but enough. At 500 mb a shortwave is forecast - PVA noted in previous post. Again winds will be okay at 500, not really strong. Perhaps the speed shear question is why SPC did not highlight Sunday for Day 4.

Sunday the lower levels look a little better than upstairs. LLJ is forecast to be robust. Surface winds also back near boundaries and any mesolows that can become established. Saturday night rain should sharpen the WF and/or create outflow boundaries (OFB). Expect a boundary intersection on the Plains which could be a focal point for supercells - perhaps the cell of the day. A tornado or two is also possible farther east along the WF. Also back in upslope land a cell could surprise. Finally if cap breaks isolated supercells may fire on the DL. Models have scattered down the DL but that will depend on bullish shortwave timing. Cap is noted, but models insist on isolated to scattered cells down the DL.

Thanks to excellent low level shear, triple point should be a fairly high probability of tornado (15% hatched) but could be messy, high-precip, numerous other cells, and/or chaser convergence. May 11 was busier than I expected in Nebraska. WF may offer less chaser convergence, and maybe less rain coverage, but still risks high-precip and/or messy. Upslope area could be a Plan B if it is messy farther east. One could argue play the DL more isolated. If a second sfc low develops on the lee trough, the DL would be great thanks to more turning of winds. Otherwise, one might want to try farther north. Personally I love DL/OFB intersections, but that will depend on Saturday night.

 

[Taylor Wright]

Been watching this day for awhile on the GFS, as it looks to be the only day I can chase of the first of a multi-day event. Have a few problems with this setup, though. With dews forecast around 60 F along the dryline by both the GFS and the NAM and temps in the 90s, I'm not sure how storms are going to break through the cap that will be in place along the dryline anywhere besides along the cold front in western NE/southwestern SD, which could end up being forced, high-based, messy stuff. Upper-level winds are backed up there after 4 pm. 2000 m LCLs along the dryline aren't favorable, but I tend not to weigh as much on that because there always seems to be a small area with lower LCLs that pops up closer to the day of. Low-level rotation isn't particularly impressive, however the LLJ is strong and winds back as the afternoon rolls on in Nebraska and Kansas.

Sunday is a tough day to target. Capping and LCLs seem to be the biggest issue. Might end up between Colby and McCook, or farther east between Phillipsburg and Holdrege. Northern Nebraska could be decent too but I can't feasibly drive up there having to work at 7 am the next day. Giving Sunday a chance since I have to work the rest of the week.

 

[Mike Smith]

The European looks better than the GFS for Sunday with thunderstorms breaking out in the afternoon and evening more or less from MCK to Greensburg.

 

[Jason Persoff]

SPC has highlighted a large swath of SLGT over most of the western plains states. I'm going to limit my forecast discussion to the area that strikes me as my target for the day: KS/NE.


The 12z NAM indicates two disturbances rotating over the Rockies: a small one to the north that will cover most of C WY, and a stronger, broader circulation over S CO into W KS/W NE. All in all, the winds speeds AOA 45 kts are in a very narrow corridor, but should at least aid in early anvil ventilation. Though others can correct me, when this narrow a corridor exists, convergent airfields could favor subsidence or storm consolidation as they move east.


700mb cap is much more intense than earlier models suggested, exceeding 12 deg C over most of the region, weakening slightly east of a Colby-Kearney line which coincides with a narrow area of less intense CIN and fairly robust CAPE.


Convergence about a surface dryline will be maximized at the CO/KS borders by 21z, but a big negative is sfc flow parallel to the dryline. There is a hint, at least this far out, of a possible small area of SE winds developing in the I-70 corridor by 00z. The hodograph for the area around Colby KS looks like this:


http://climate.cod.edu/data/forecast/sndgs/12_NAM_060_38.86,-100.16_hodo.gif


The more favorable surface winds are about a triple point in S SD/NC NE. But that area is also much more challenging chase terrain, and may be hampered by much less capping (thus risk for more convection).


Initial target: Colby KS-Kearney NE for Sunday night. Thoughts?

 

[Andrew Stoller]

I agree Jason; the NAM is trending more southerly with the 500 mb flow; the base of the faster 500 mb flow coincides with sub 1000 mb surface low over eastern CO, and although, like you say, dryline winds are parallel to the boundary at first, surface cyclogensis really ramps up in the 00z time frame and winds back substantially leading to 550+ 3km helicity after 00z in western KS. There looks to be a stronger impulse in the flow as well leading to a small area of 50+ knots of 0 to 500 mb shear. The setup will either favor an initial discrete monster super cell or it will rapidly pool out into a compact strong MCS. If intitation can hold off due to the cap until between 21z to 00z, there might be a small window for well ventilated inflow dominate convection until outflows/cold pooling undercuts everything. My target will likely be Dodge City to Goodland as it stands; will try and stay just southeast of convective initiation area. Whatever does go up will be moving southeast as the area will be right between the northern trough and the southern ridge axis' in some spots the shear vector is almost due south. Theer also is a nice compact dryline bulge into western KS after 00Z owing to strong surface cyclogenesis. 03Z Mon hodograph for Dodge City:

 

[Taylor Wright]

Here's a the hodo and skew-t forecast right on top of Ness City, KS at 4 pm tomorrow. Instability is over 2000 j/kg and cap is negligible at 4 pm.

http://www.twisterdata.com/index.php?
sounding.lat=38.4549&sounding.lon=-99.9058&prog=forecast&model=NAM&grid=221&model_yyyy=2014&model_mm=06&model_dd=01&model_init_hh=00&fhour=21&parameter=WSPD&level=10&unit=M_ABOVE_GROUND&maximize=n&mode=singlemap&sounding=n&output=image&view=large&archive=false&sounding=y&sndclick=y

Road networks and terrain are beautiful over there. It's been since 2012 that I've been able to chase in western Kansas. Both tornadoes I caught this year were in Missouri. Very bummed that I'll have to sit this one out. It's definitely tempting to take the 3 hour drive solo over there, but I cannot put my life on the line relying on T-Mobile data for navigation and radar, or anything for that matter, all while driving. I'm lucky to get Edge data anywhere except for the bigger cities in Kansas. Those of you who are able to run radar, navigation, and call in reports all while staying on a storm, I greatly admire you, but I simply can't safely do it. So, if anyone around the Wichita area wants to meet up tomorrow, shoot me a PM.