jpeters3

cell behind it tightening up

debris signature on mccomb storm

It's really an issue of low-level buoyancy. If you can get enough low-level buoyancy, that aids (or at least doesn't act as a deterrent) in the vertical stretching of near surface vorticity, then you are golden. Likewise, weaker low-level laps rates equates to less low level acceleration and makes it harder to stretch near surface vorticity. So there may not necessarily be a CAP (there could be no CIN), but it's still hard to punch through the layer with very weak buoyancy. It is possible for low-level dynamics to overcome this issue, but we don't really have a good understanding at this point of which conditions do, and which do not permit this "compensation." For those of you who are more technically inclined, it's not actually the low level buoyancy that does the near surface stretching. It's actually the buoyancy-driven low pressure that sits at the updraft bottom, and the associated upward accelerations below the updraft base and the center of this low pressure. When low-level buoyancy is stronger, this low pressure feature is also stronger. Note that this effect is separate from the low-level dynamic accelerations driven by rotationally driven low dynamic pressure.

He has been touting that for days, but obviously they are limiting things here.

Thanks!

Unfortunately you can't view KULM on radarscope...

trying to fire ahead of main line

This is a very good point. The 15 UTC HRRR is a little too far north, a little slow, and seems to be a little too discrete with this QLCS convection. Hard to tell what downstream impacts this might have, but it make me a bit skeptical of that solution.

worth noting that a robust ofb is evident along the SE flank of the line. This means that tail end spin ups along the line are unlikely.

15 UTC HRRR is breaking out a line of supercells ahead of the QLCS in the volatile part of the warm sector....

Obviously SPC outlooks have no impact on what will actually happen, but it's fun to speculate on what the SPC forecasters will do.

Though, the HRRR solution is showing a lot of this activity (aside from the huge UH tracks with the QLCS) along the tail end of the line. So far, this region as been fairly inactive. Edit: after another look, I'm having trouble interpreting what the model is showing. At one glance, I can convince myself that it shows widespread supercell coverage. At another glance, I can convince myself that it's just showing a QLCS mess. Either way, it seems every probable that numerous QLCS tornadoes will happen today given this morning's trend, and that some of them might be strong. That alone, along with the more uncertain warm sector, might be enough to warrant an upgrade to HIGH.

It's also worthy of note that the sounding is nearly moist neutral below 2.5 km, so it's likely that also helped things. Parcels in moist neutral environments should have no resistance to ascent, and do not experience deleterious effects from entrainment. Could be a totally different story for a sub-saturated environment with a similar low-level lapse rate.

new circulation

Seems like this was a fairly "hefty" QLCS tornado....

Here is a forecast sounding from the RAP that is probably representative of what the QLCS is ingesting.

OK, so it seems like intense QLCS tornadoes are on the table today...

I don't envy the forecaster seat in these types of events.

Yeah, this seems like it should stay MOD (at least for the next outlook). Only scenario I see for an upgrade to HIGH is if there is the beginning of an outbreak underway.

I don't think it's trending anywhere right now. Same story as yesterday. High ceiling, but potential for bust as well.

FYI, my former PHD advisor's group at CSU runs a 4 km WRF that uses GFS as LBCs. The simulated radar reflectivity loop can be found here: http://schumacher.atmos.colostate.edu/weather/real_time_wrf/radar_1km_4km/anim.php UH tracks:

I don't know - one could argue that a lot of these are discrete cells, and there are A LOT of UH tracks. This could indicate an outbreak.