7/18 NOW: ND

[Jeff Snyder]

I doubt anyone on ST is chasing up there now, but worth a shot...

A strong cyclic tornadic supercell continues to move south-southeast across eastern SD. Another right-moving supercell is currently dissapating as it moves into SD, right the left-split also beginning to dissapate. Multiple tornadoes have been reported with the first large supercell in eastern ND. SPC Mesoanalysis shows strong instability in the area, with CAPEs >3500... Add'l strong low-level shear remains, with 0-3k helicity from 200-350. That large tornadic supercell, currently quite isolated, will likely remain tornadic for some time longer, before increasing nocturnal cooling yields increasing low-level stability, and the supercell becomes elevated. The other, earlier supercell that looked like it was trekking into SD has fallen victim to the cap, as indicated on the Aberdeen 0z sounding, which isn't very supportive of surface-based convection...

 

[mikegeukes]

13 reports of tornadoes in the LSR's so far for North Dakota

Mike

 

[Jeff Snyder]

Meso remains strong with that storm... (un)fortunately, it's moving HARD right and is now moving southwest! This will take it into the outflow of the supercell to it's southwest in the next hour or two, likely resulting in signficant dissapation. Granted, depending upon what happens with the supercell to its southwest, which is just at the ending stages of absorbing the left-split from the now-disappated storm to it's southwest, the awesome cyclic supercell may be able to ingest helicity-rich air courtesy of baroclinically-induced vorticity on any outflow boundary from the southwest storm...