I just checked the 5/11 OUN 21Z sounding and I so see that the Buoyancy value was very marginal. I guess this is a Meteo 101 question, but: what is the cue that parcels are not surface/PBL--based?
The 21Z profile does not look like one I'd associate with elevated convection. I've always assumed the phrase "rooted in the boundary layer" to mean that surface-based (or parcels originating in the boundary layer) can reach the LFC, whereas elevated convection occurs when PBL-based parcels cannot reach the LC but an elevated parcel can. Here's what I mean. In the image below, the yellow bands represent layers which satisfy the Carlson-Lanicci criteria for EML transition layers, and the cyan bands are layers where the static stability is ≤ 4.5˚C/100mb.
What prevents surface based parcels from reaching the LFC (which is about 900mb, give or take)?
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BTW--I do appreciate the help understanding what's going on so I can make the most of my opportunities to get out and observe storms. Thank you.