5/11 Extended Forecast

051117 Extended Forecast

It looks like next week will likely be the most active week for severe weather that we’ve had in the plains so far this year. How extensive any tornado threat will be is still a bit hard to judge since finer scale details are a much bigger factor in determining tornado potential, but the large scale pattern is obviously supportive of several rounds of a more general severe weather threat.

The Gulf of Mexico is going to take a beating this weekend as northerly winds on the back side of the east coast trough push dry air south. Low level winds don’t start to become favorable again for better quality moisture advecting back into the plains until Monday as a high amplitude west coast trough begins to nose into the plains.

Monday is the first day of interest, but it’s a lower tier of interest lol. I’m afraid moisture quality is going to be an issue. A dryline will be tightening up over the western edge of the plains, but it doesn’t look like there will be enough time for better quality moisture to move into the plains and pack in along the dryline by Monday evening. This will largely preclude any tornado threat that otherwise would exist. The GFS has been showing some precipitation along the dryline, so it is something to watch, but I would expect any tornado threat on Monday to be lower end. I could be wrong though. Low level shear will be quite strong, so if we can get storms off the dryline and they can work out into better moisture over the warm sector before the boundary layer decouples, then that could possibly open the door to better tornado potential. The primary area of interest for Monday should he ahead of the dryline from central Kansas down into the Texas panhandle, which I’ve highlighted on the map above in yellow.

Tuesday looks to be a bigger day. It’s still a long ways out so you can’t take details too seriously yet (let’s not forget how many times the GFS has burned us this year and prematurely started the hype train #choochoomotherfuckers lol). That being said, the GFS and ECMWF have been consistently depicting this as a fairly strong trough transitioning from a neutral to a negative tilt as it ejects into the plains Tuesday afternoon. That should get your attention when it happens in May. I am concerned about moisture quality a tad. I do not think moisture quality has any real shot of being a deal breaker for Tuesday, but it could be a mitigating factor. With higher end setups like this, the difference between a couple strong tornadoes and a major outbreak can be slightly better moisture quality/very strong instability vs. just moderate instability. Right now it looks like a moderate risk type tornado day. Stronger instability or shear profiles being a little better could easily nudge this up into more of the major tornado outbreak type parameters though. It also looks like this could be a fairly widespread event. The best tornado potential has been focused either side of the Kansas/Oklahoma border area with the GFS, but parameters supportive of tornadoes should exist across a large area ahead of the dryline from North Texas up into Nebraksa. It’s a textbook plains severe weather setup. It looks good enough that I canceled a business trip I was supposed to go on Monday and Tuesday so I could make sure I was here to chase. I don’t miss major tornado days in Kansas and this setup is showing the potential for that at least. Again it’s a long ways out and a lot can change, I’m just saying the potential is there for a moderate to higher end tornado setup. It is still a little far out to get into any real detail, but I’ll just hit on the handful of things that I do think you can put some weight in and are raising red flags for the severe/tornado potential. As I said above, the models have consistently shown a high amplitude trough that is taking on a negative tilt as it ejects into the plains. That’s important. The strength and tilt of the trough along with moisture availability are the biggest things I watch in longer range forecasting. The mid level jet associated with this trough is forecast to have 500mb winds in the 55-60kt range Tuesday. That’s good, but it’s not great. A lot of the major outbreaks this time of year have 70kts at 500mb, so again good, but not great. Dewpoints are forecast to be in the low to mid 60’s, which should get the  job done. It’s not ideal, but low 60’s would get us by for a solid tornado threat. With the trough just taking on a negative tilt we should have stronger wind fields over the warm sector, but still have decent directional shear to work with (when you start to get a more negative tilt you loose the turning of the winds with height). And finally the broader details would imply that neither morning storms working over the warm sector or storm mode should be problems. With a north south dryline and storm motions to the northeast, discrete supercells are very likely to be the favored mode of convection during the evening. Alright, so just to sum things up in my opinion if you take the models literally at this stage 5 days out, it looks like a moderate risk for tornadoes to me (I’m speaking in SPC terms, if you don’t know what that means then you probably don’t need to know). I’m keeping a close eye on this setup so I should update regularly.

After Tuesday, my attention is focused on Thursday, Friday and Saturday as the west coast trough fully moves into the plains. There will be severe weather chances in the plains on Wednesday with SW flow aloft, but I look at it as more of a lull in the action between the two primary troughs moving through the plains. Thursday looks like there could be some good dryline storms across the western plains, with SW Kansas and Texas looking like the best areas. Friday looks like it could be a more widespread severe weather event. I’m a little concerned about shear profiles and how favorable they’ll be for tornadoes since mid/upper winds may begin to back and take on more of a meridional flow look. Another potential issue is precipitation over the warm sector botching things on Friday and Saturday. That always seems to be an issue with multi-day negative tilt troughs like this and a lot of times it tends to push the best tornado potential a little farther south than you may have anticipated to where the southern edge of where earlier storms tracked through and moisture quality with uncontaminated air is better. For that reason I’m thinking the greatest tornado potential for Friday may end up being down in the southern Oklahoma and north Texas area. That’s a total guess at this point btw lol. Anyway, we are looking at tornado potential on any one of those three days from Thursday through Saturday. I’ll start to get into it more as we get closer.

Alright that’s it for tonight. I should pretty much be posting daily now that we actually have something to talk about, so check back for updates if you’re interested.

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