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Plains trip #1 looking like a "go"
Models have not changed much regarding the upcoming pattern. Now that we have two runs of the NAM/WRF to go on in addition to agreeing runs from other models, confidence is very high for at least two solid storm setups in the Plains/Midwest by Wednesday, and possibly as many as four. By all indications, the April 7-9 Plains trip is a 'go' barring the most extreme of model forecast busts.
The event begins tomorrow (Sunday) with a conditional setup in Kansas and Oklahoma, followed by Monday's setup in generally the same area. There is no question we will have good storms somewhere in the Plains tomorrow, but moisture quality and resulting instability have me on the fence about whether it will be better to stay in St. Louis. We may have equal "storm photogenics" chances here in the form of lightning Sunday evening.
Monday has consistently looked like this system's best day, with the highest combinations of shear and instability. Tuesday has the potential to be a big day as well in Kansas, Oklahoma, Missouri and Arkansas. Tuesday's instability looks generally weaker, but shear should be better than on Monday to compensate. Finally, Wednesday has some potential in the lower Midwest (Illinois, Indiana and Kentucky), though right now this appears to be an early-day squall line event due to unidirectional wind profiles. Speed shear will be strong on Wednesday, however, so tornado potential will have to be monitored. The trough could bring an additional round of severe weather farther east (out of my expedition range) on Thursday from the Appalachians to the east coast, though weak instability is shown to be a limiting factor there.
As for my expedition plans, Monday's setup is definitely a 'be there' event as far as I'm concerned, despite possible moisture and/or capping issues. I am still on the fence on what to do about tomorrow (Sunday). I likely will not make a call on a tomorrow's "stay or depart" decision until the morning, when I can get a good look at how the low-level moisture situation is evolving in real time (via the surface obs). Either way, I am planning to be in the Plains for Monday and Tuesday. If the local lightning option looks like the best play tomorrow, I'll depart for the Plains before sunrise Monday morning (it's definitely nice to live within a half-day's drive of Plains targets!). If tomorrow's surface obs show a better moisture return situation, I'll skip out on St. Louis lightning and head for Sunday's Kansas target.
Whatever happens, it will be the first true multi-day chase adventure of 2013 - and there will be plenty of action, be it tornadoes, hail and/or lightning. Stay tuned to the Facebook and Twitter page for live updates when internet access allows!
Looking ahead again in the midrange period, a second big western trough following on the heels of this one is still indicated by models. This next trough is shown as being very robust, and will very likely provide at least one or two solid tornado setups as it swings through the center of the US between Monday the 15th and Thursday the 18th. My ability to observe storms this next system in the Plains may be constrained by work, however, so I am hesitant to go too high with chase probabilities. Even if I scratch a Plains trip for these dates, a couple of Midwest opportunities are almost certain during the same time for lightning and possibly tornadoes. Midwest setup expeditions thankfully aren't affected by my work schedule.
The following table charts the probability of a Great Plains weather expedition for the indicated date ranges:
|2013 Plains Storm Expeditions - Probabilities as of April 6|