April 21 Forecast Post

Sunday dewpoint

Really not many changes to make to previous forecast posts regarding Sunday. The first volley in what looks to be a very active severe weather week ahead will come on Sunday as a short wave trough with an associated 55kt jet streak moves into the central plains. A NE to SW oriented dryline will be the focus for convection during the afternoon. Storms may be a little clustered in coming off the boundary from SW Iowa into central Kansas, but they should tend to get more discrete as you go south where forcing is weaker and 700mb temps are warmer. I think the NAM is juicing the moisture return a bit, but dewpoints around 60 seem reasonable into Kansas at least. The best potential for Sunday still appears to be around the central portions of the dryline where moisture/instability are best overlayed with decent deep layer shear (on the southern end of the mid level jet) and convective evolution appears to be more favorable for discrete supercells. That area is boxed in red on the map. In addition to this area being the best compromise of deep layer shear and good thermodynamics, both the NAM and GFS want to locally back winds ever so slightly around dark as a secondary surface low develops over SE Colorado during the afternoon. It’s a minor little detail, but it’s something to watch and it does look like surface/925mb winds back a little late in the day over south central Kansas and north central Oklahoma in response to this. That along with the nocturnal LLJ ramping up should put the greatest tornado threat around the 7-9pm time frame. This doesn’t look like anything major, but I do think we have a decent shot at a few lower end tornadoes Sunday afternoon/evening.

Attention then turns to Tuesday. Tuesday does look like a pretty nasty setup given the strong instability, good quality moisture and good shear profiles, but I don’t quite get just how big of a deal some people are making out of it on social media. It’s a tornado outbreak type setup showing up in the models. It’s not unprecedented. Act like you’ve been there before lol.

Tuesday Map

I threw a quick map together with a few notes so just click on the image to enlarge it if you want to read the details. I need to get to bed so I’m not going to talk about it much. It’s a solid setup with good quality moisture and strong instability being it’s best assets. It also looks unlikely that morning storms will screw this one up, which has been a frequent problem going back to last season. Dewpoints should climb into the upper 60’s ahead of the dryline and with good surface heating instability will be strong. Combine that with low LCL heights, good deep layer shear, solid low level shear and a dryline that should put off numerous discrete supercells with good spatial coverage and bam, you have the makings of a tornado outbreak lol. Still a long ways out, but tornadoes look like a good bet on Tuesday. I am nitpicking a bit, but I do think slightly better shear profiles are what’s keeping this from being on par with some of the more well known high risk/major outbreak days. I think strong tornadoes are a good possibility, I just don’t think this is like an epic setup like I’ve seen a few people make it out to be. It looks like a high end moderate/low end high risk type setup if you want to go by SPC type criteria. I think the tornado potential looks all about the same from the dryline bulge south through Oklahoma. I feel like I’ve been in this situation before and I already know the dilemma that lays ahead for me. I have a rule that I keep Wichita in range on any days where there is a strong tornado threat for the city. I’ll venture out a ways from Wichita, but I always keep a close eye on satellite and radar to anticipate if a storm may go close to town and make sure I keep it in range if I need to head that way. Well Wichita is right in the wheelhouse for this one as things stand now. I also tend to favor moving south down the dryline with setups like this, but I already know that won’t be an option for me on Tuesday because I’ll have to keep it close to town. I do like the central into northern Oklahoma area along I35 better, but I know I’ll stay in south central Kansas so I can help with coverage.

Anyway, that’s all for tonight. Sorry I didn’t get into more detail on Tuesday’s setup or get into the other chase days that will come behind it next week, but it’s midnight and I’m ready for bed. Check back tomorrow and I’ll get into some more detail.

 

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