2015-04-01 EVENT: NE/KS/IA/TX/OK

No April Fool's here, there might be some storms to chase on Wednesday.

SPC has dropped a SLIGHT across much of the Missouri Valley for Wednesday afternoon. Local office discussion has a mention for 2-3k cape and deep layer shear, supporting a forecast for severe weather. This leaves me with two major questions. 1: Will there be enough moisture return? 2: Will storm motions (forecast to be ENE), be far enough away from the squall / LCS to maintain rotation?

I don't think shear will be a huge issue. NAM was very bullish last night, with 1k EHI's in the 3-5 range in E Neb, but has pulled back quite a bit on the 06z and now the 12z. GFS has been a bit less eager to forecast shear, but there is still enough given the cape now forecast. As for moisture, based on the speed of the 850's I think that a 60 dewpoint is possible ahead of the main line, and 60 is a good cutoff in Nebraska for TORs (possibly even lower due to the LCL's that are forecast to be <1000m.)

Storm motion is going to be the tricky one here. Cell speed will likely be slower than the LCS, and ENE motion is barely off of the expected SW/NE orientation of the front. Inflow and shear may be compromised by the proximity or cannibalized by the line. There is enough 3k helicity to support supercells, possibly weak tornadoes, but cells will likely only maintain rotation if they can form ahead of the main line in W IA, far SE Neb, or Ncentral KS.

Your Best Chance of a Tornado Wednesday: Tail - End Charley in Scentral NEB / Ncentral KS. (Hebron, NE)
Although dynamics may be a little better to the north and east, it will be a mess up there, in particular if there is AM precipitation leftovers. Don't forget low LCL's means rain-wrapped HP's if cells do hold together. I'm not super confident that we'll even get a TOR at all Wednesday, but for many of you this will be the first or second chase of the year, so why not? Sadly I'm working.
 
As Royce mentioned, this appears to be quite a long shot day in terms of tornado potential. I do not like the 500s especially for April 1, but they do get stronger the further north you go. Instability appears that it is going to be decent, but pretty well capped ahead of the main forcing so getting something to form ahead or south of the main
line that is forecast to develop might not happen. Latest NAM does want to develop storms further south though, so I think it may be necessary to eventually add TX/OK into this thread. Possibly even MN as well. If nothing else changes for this day, I may target somewhere in southern MN to keep it local and not expect much at all. Like Royce said though, one good thing about the farther north you go, you get better dynamics. It'll be interesting to keep an eye on this day. As of now I would target Worthington, MN and hope for something interesting as storms first fire.
 
MODS: Please add TX and OK to the thread title

Not really sure where to begin on this one, looks like the dryline will likely be stretching from Quinter down through Shamrock down to Del Rio. Overall moisture quality through 1.5 KM actually looks surprisingly good out west on the dryline in the TX PH/W OK but the upper level support lagging well off to the west on the southern end of this may kill things. 35 knot H5 winds progged by the 12Z NAM with the main forcing still well back near the Four Corners by 00Z. LCLs look like they may be a touch high out that way with surface temps hitting the mid-80s over low-60s dews. The sfc cyclone would is in primo position in SE Colorado and deepens to a 996 mb low by 00Z with 10 knot sfc winds along the dryline backing out of the SE. MLCAPE looks kind of meh, just nosing 2000 j/kg from Sayre to Arnett. The LLJ looks damn impressive going into the evening, it just looks like the dynamics might not be there in time.

Tentative target: Arnett, Oklahoma
 
I have a hard time seeing anything stay discrete in KS or NE with upper-level support being 200 miles behind the boundary. Not to mention much of the forcing will be that of the cold front. Definitely not a good day in terms of tornado potential. The NAM has been decent on guessing dewpoints lately, so going ahead and assuming they are in the 55-60 range, I can't imagine storms will stay surface based with temps all the way in the mid 80s. However, the kinematics are there for some low-level rotation, and if anything can stay discrete, say in SW KS (the NAM has some discrete action there after dark) or along the dryline in OK, then things could change quickly as temps drop.
 
Agreed Jeff. The absence of the 500 MB jet in most of Kansas and Oklahoma flushes down this day's set up. A couple of days ago I was actually excited about this day but the weak mid-level winds and good chances of the cap holding kind of messes this thing up.
 
Planning on being out somewhere north/north central Iowa. don't like any of the set up further south...looks like the cap will be too strong and will hold throughout the day. think there will be better storm dynamics towards IA/MN areas.
 
So here's my update following the 12z Nam.

Across the board, EHI's have gone up significantly, in particular the 12z NAM looking for 0-3 EHI around 7-9 in NE Neb around 21z and Central KS around 00z. Moisture appears even more plentiful than before, with most areas above 60. Notice there might be some drying in KS due to heavy mixing, possibly capping till better shear arrives around 00z. Solid Cape is now forecast down into NC OK, and the cap is forecast to break, only shear is missing from a high quality tor forecast (and it may arrive after dark).

My Modified targets for Wednesday:
NE Neb (Norfolk). (if you can get a cell to form ahead of the line.) NW Iowa might also be a good play, but the roads there terrible and I refuse to chase in Iowa. Keeping away from the looming LCS may be an issue. Further SW into central Nebraska you may hit a tail end Charley at the end of the line that has good inflow. Beaver Creek, NE TOR last year was similar positioning, with the TOR riding ENE along the bottom of an MCS. Keep in mind, LI's are going to be very high (-10 or -11). Strong updrafts means big hail possible. There's also a dry inversion at 700mb, so downbursts in addition to straight line winds are possible. Messy Messy Messy....

For you southern plains chasers: Hang around Wichita and wait for the cap to break. The best shear should be just north of you by 00z, and the dryline should be lighting up. The other option is to hit N OK where storms will likely be firing, but may be multicellular...and the lcl's are looking a little higher. Not perfect but you might hit something.
 
Tomorrow looks like a good day to chase if you want to get your car destroyed by hail. That's if updrafts can stay isolated long enough to produce it. 20 kts of bulk shear, LCLs above 1500 meters... no thanks. Looks like a line will get forced up through the cap, resulting in maybe a handful of severe reports. Pretty pessimistic about tomorrow.
 
Looks like the models may have played an April Fool's joke on us. Update Per 12z NAM

The huge influx of moisture by 21z and 3k Cape's are gone per NAM. GFS is still holding strong and putting the front near Omaha by 7pm. Not going to happen. Nam forecasts front to hang back til way after dark. Moisture doesn't arrive until after 7pm, and shear is pretty weak until the LLJ kicks in. Expect, as the NAM predicts, a squall line to form from C Neb to NW IA. There may be some storms down on the dry line, but even those are iffy now.

Our best chance of a Tornado for the day: NAM and friends keep showing one or two rogue cells out in SE KS or W Missouri. If they are riding leftovers from AM or on that little warm front you might see a spin up from the localized vorticity. Otherwise you're gonna have to wait til late in NE and KS. 60 DP's arrive by 9pm into SE Neb, shear goes through the roof with the LLJ, and 1000-2000 Cape will likely still be untapped due to capping from the inversion earlier.

If you hang around till dark, you might catch an outflow from the LCS to the north banging into the LLJ and get some short lived tors, possibly even one or two solid supercells from the dryline going tor as they move into more favorable conditions in NE KS extreme SE Neb. The front has slowed down significantly from the forecast, so that's a bonus because you're less likely to get undercut, but your targets have also shifted MUCH further west or much later.

So what went from a borderline chase day turned into a hope-you-like-lightning LCS fest. Good Luck guys.
 
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