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Central/Western Medium-Long Range Discussion

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Sunday and Monday looks like plenty of CAPE. What about turning with height? What makes the composite parameter soar? Is it CAPE without good turning? Is it turning on a warm front with cloudy stable stratoform rain? Obviously the former is much more likely than the latter this case (CAPE chart previous page); however, the latter happens often early season. For legit severe we need both juxtaposed. 

Is turning with height forecast? Let's take a look at the Central Plains both Sunday and Monday on the ECMWF.

At 250 mb winds are seasonable (modest but not dead) from the WSW. At 500 mb a short-wave passes Sunday but winds weaken Monday. Both days 500 mb is WNW. Despite AN heights, 700 mb is not too hot. 700 mb wind is also from the WNW. Sunday and Monday 850 mb is straight south (good) but modest. Surface and 925 mb are from the southeast.

So, we have great turning with height from surface to 700 mb. Winds are not too strong however. Pretty sure not tornado outbreak. Actually this is what late season chasers seek. Keep it subtle. Avoid crowds. Maybe find an isolated gem. Veer back is forecast from 500 mb to 250 mb; however, that high up is not a deal killer. It's especially OK late-season vs early. 

I've already taken my chase trip and found what we sought last week. I think the weather pattern looks good for those out there late-season and/or still looking for their tornado; but, it is not good enough to justify another trip after seeing a two-cycle tornado event last week. Who knows? Maybe a CO/WY gem could happen in upslope flow.

Best to check all constant pressure level forecast charts in the extended. Forecast soundings are worthless past 36 hours, esp if convection contaminates. Constant pressure level forecasts are OK a few days out to discern forecast turning with height (or not).

At the very least, check both CAPE and Helicity forecasts separately for juxtaposition. The latter forecasts turning with height, but even it can mislead if speed overwhelms no turning. Composite parameters are not that useful. So, drilling down (or up) the constant pressure charts is best.

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The overall pattern looks unseasonably quiet across the Plains through at least the next 5-7 days. This is reflected well by the CFS severe weather guidance dashboard, which has blue boxes in the coming days, something that is very unusual for early to mid-June.

The Northern Plains area into the Upper Midwest may see some severe thunderstorm activity this weekend, as a trough ejects eastward. What happens with that trough next week is the glaring issue. Medium-range guidance and ensembles are fairly consistent with broad troughing across the Missouri Valley/Midwest/Great Lakes vicinity through much of next week. In uncharacteristic form for mid-June, instability appears limited through at least the middle of next week and possibly the end of the week as well. Northwest flow events tend to become more common into July and sometimes even mid to late June, but with modest instability, at best, that does not bode well for severe thunderstorm prospects via NW flow next week.

As we approach next weekend, there have been signs that the pattern shuffles and there could be a return to at least near average severe thunderstorm activity for the third week of June. European ensemble data and the weeklies, to a lesser degree, show a more zonal flow-type pattern across the northern tier of states by next weekend or early in week 3. (roughly the June 15-18 window) The potential may exist for one or perhaps a few shortwaves to impinge on the northern High Plains/Northern Plains vicinity with an uptick in severe potential there. This is also highlighted by the CFS dashboard, although it does not take much in the way of wind shear to throw blanket regions of elevated SCP values in June when there is seasonably-typical instability in place. (The CFS dashboard is based on supercell composite parameter / SCP values, either over a broad area or elevated in any area)

On the other hand, the latest Euro weekly data seems to imply that any pattern shift is short-lived and that more Upper Midwest/Great Lakes troughing could set up by the middle or end of June week 3.

As we go deeper into June, the Great Lakes/Midwest vicinity could experience northwest flow severe threats, but that type of pattern needs instability in place. The trends suggest that moisture is going to be scoured south and east (quite a feat for June), even when there is appreciable upper level flow in the northern states. Who knows, maybe that could result in an unusual late season threat across the Mid-South, but that's speculation on an already conditional scenario.

Any way you slice it, the prospects for severe thunderstorm activity in the Plains in the near future are very slim. Sure, you can get some High Plains magic here or there, but that's to be expected, even in the quietest months of June. I'd be cautiously optimistic about prospects for June week 3. On the bright side, that period (June 16-22) has featured some significant events over the past decade. Almost each year seems to have at least one noteworthy event in that window, but we'll see.

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Early June has been very quiet for most of the 2010s, the exception being 2010 itself.

I definitely think the latter part of next week will have a chance beyond the amplification of the ULL near the Great Lakes. There is a strong signal in the GEFS for at least some activity in that period (and there has been for awhile), and note that the GEFS SCP chiclets on Gensini's website are anomaly based, rather than using raw count, so it gives a better idea of elevated activity relative to climo. Signal on the EPS is rather nebulous, but I wouldn't expect a really large signal in the heights at this point since it looks to be more centered around subtle disturbances in the flow.

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ECMWF still points to a little more activity starting on Friday, and through the end of the model run. ECMWF Para/Beta (2nd deterministic) looks even a little better. The latter keeps westerly flow instead of that northerly junk end of EC Op. Both have modest LLJ response most days starting Friday.

Moisture quality is slow to return, but by Friday is enough for central/high Plains. Moisture gradually improves each day, esp on the EC Para. Given what happened Saturday, Colorado and Goodland, chasers may be able to seek meso-scale events again. Good luck to those June-ing!

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New ECM (12z run of the Para) forecasts environments next week that would corroborate with the impressive GEFS SCP chiclet charts -- possible hyperactive end to June? 

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I put my chips on 3-4 chase days next week. However I don't see any big outbreaks. It is typical June chasing, but could be quality chasing.

First half of the week starts with the Upper Midwest. Tuesday the ECWMF shows a true system in chasable terrain of the Northern Plains. Wednesday goes into the MN/WI forest, but maybe something can get going down in Iowa. 

End of next week moderate flow is forecast to remain in the Plains (almost unseasonable NE/northern KS). LLJ is forecast to respond. Might get a couple days out of that if cap is not thermonuclear. Placement is uncertain attm.

So I propose we have two pairs of possible chase days. Take out one for terrain and/or bust. Nets 3 chase days?

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Did not see a recent banter thread so thought I would just post here. This new video by Pecos Hank discussing super computer mesocyclone and tornado genesis with Dr. Leigh Orf is an absolute must watch:

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