June 8, 2016

Team Turtle's Forecast:

"Brindley and I did a run through the 0z NAM. Seeing two potential targets for tomorrow within range:

1. Blacks Hills. Moisture advection and upslope flow from some easterlies at the surface looks to initiate storms over the high terrain of the Black HIlls by mid afternoon. Capping over the lower terrain and weaker flow aloft looks like it may confine any activity to the Black Hills themselves. Brief supercellular or possible non-supercell tornado play in the hills, before storms die in the grasslands to the east, or gust out before even leaving the Black HIlls.

2. Badlands to Murdo. Looks like a very conditional chance for a warm sector play to the east. Maybe a slight disturbance aloft, moisture convergence along a dryline bulge over the Badlands. Maybe if convective temp is reached coupled with some slight upslope flow over the Badlands, we might get some high based initiation. If it tracks east/northeast into the richer moisture over I-90 and onward toward Pierre, we might have a shot at a supercell play, with a veering wind profile, moderate to strong instability, and a strengthening low level jet. 4km NAM failed to initiate this target on the 0z run, and plots indicate maybe considerable CINH. Still, the lid strength looks almost manageable, with a 1 to 0 value persisting from 21z to 3z,which should provide enough window of opportunity. Lack of lift and upper level support may make the target a dud though.

We're leaning on the Black Hills target for now, given the uncertainties to the east and the logistics of the drive. There is a great visibility over the Black Hills at the Rapid City Airport from an elevated vantage. We're going to try and hit the road by 8:30 MDT heading toward the Black Hills until we receive new orders. See you guys soon!"

Team Turtle's Forecast:

"A complex surface scenario is evolving with the approaching upper level trough system to the west. A primary surface low lies over southern SK and northern Montana, trailing a hybrid stationary front to its SE, toward the Badlands and south into NE and KS. A secondary low is analyzed south of the Black Hills, with a likelihood for easterly winds over the northern portions of this region. Early morning satellite suggests Anvil debris that may slightly slow surface heating this morning, though this should clear eastward. GFS has continually pushed this system eastward, which doesn’t seem to agree with the morning synoptic maps, and pokes a hole through cap over the Badlands from around 21Z-03Z. If storms were to fire further east INVOC Murdo or the Badlands, this may be worth a shot, but the CAMs are skeptical about this scenario. Part of the reason for the model difference relative to NAM/NAM4km may be the inability of the coarser GFS to handle terrain modification of the parcel environment or low track, which generally requires higher resolution - this may explain the dichotomy of the solutions even at this late stage. In light of this the environmental parameter space it would appear the best scenario is near Rapid City with cells forming in the easterly upslope region over the high terrain.

CAMs have slightly diverging solutions, but are consistent in initiating storms over the Black Hills and tracking east/seward, while also suggesting that any convection over the northeast of South Dakota will remain capped throughout the day, and possibly only initiate late night associated with warm advection from the developing LLJ. 00Z NAM and 11Z HRRR were fairly consistent in robust updrafts that struggle to depart the high terrain, however, given the surface based instability and easterly shear a brief tornado cannot be ruled out, or possibly a landspout. In contrast 06Z was more bullish for Robust updrafts that do manage to depart the high terrain, and maintain for at least a couple of hours - the end result may be related to the overall storm morphology. Part of this difference may be the rather bullish moisture depicted by the model, which wants to drive dewpoints into the 60s - but a surface moisture source for this appears to be in southern KS. That being said, the 11Z prediction is pretty close to what we are seeing, so perhaps it will be mixing from slight elevation or the LLJ begins to take over - either way we should know the realism of this scenario by later this morning. 12Z HRRR does want to break out convection further east in addition to the Black Hills, but as we saw the other day, whether this happens remains questionable.

Based on this and Skips synopsis, my inclination is to target the eastern Black Hills, with a view to watching developing trends in thermodynamic parameters and Cu fields if a storm were to find a home in the SB world further east, or possibly a Black Hills cell moving off east. "

Team Duck's Summary:

"We woke to cirrus skies and a pleasantly cool morning. An easterly moist upslope environment was projected to develop on the northeastern side of the Black Hills of Dakota. This was expected to yield a CAPE environment of 2000-3000j/kg under a relatively stout capping inversion. Model solutions appeared to diverge, with GFS seeming to struggle with the importance of lee low development near the Black Hills, contrasting the NAM solutions. Morning satellite showed anvil debris over the region clearing to the east. The question today was - would storms over the Black Hills be able to sustain themselves and move out onto the plains, or would they struggle against the capping inversion and relatively modest vertical wind shear.

Surface synoptic maps at 11:30am MDT revealed dew points as high as low 60s in northern NE advecting toward the Rapid City region around the low centred in the west NE panhandle with a frontal boundary draped just north of Rapid City along i90 and defending south through central NE. Visually, already on the Black Hills, two airmass thunderstorms formed over the elevated terrain and looked quite healthy.

Cells continued to intensify over the Black Hills, showing potential to move towards the edge of the higher terrain as we closed on our target of Rapid City. We drove through a weak dust devil on the way north to Hermosa. Unfortunately, as time marched on, weak airmass thunderstorms were the only things to form given weak vertical wind shear and potential large scale subsidence. Given the positioning for tomorrow’s target, we elected to call the chase for Dickinson ND."