June 12, 2016

Team Duck's Forecast:

"Day 1 Outlook: Marginal potential will exist over eastern WY and NE Colorado, and in the corridor extending from MN to NE Colorado. A initial cluster/line will form along a frontal boundary roughly extending from MN to NE Colorado, however marginal shear, particularly through NE and eastern CO will likely preclude much in the way of significant severe risk. Over the high terrain of WY and CO, shear will be somewhat more favorable, with weak upslope flow promoting dewpoints into the mid-high 40s, and SB CAPE toward 1000 J/kg, with 40-50 knots vertical wind shear based on the latest HRRR runs, though much of this is found in the mid to upper profile. This will particularly foster NE moving storms to the east of the Douglas-Cheyenne Ridge region, with the shear potential the best in this part of WY. These cells will likely be absorbed with time by one or more upscale growing clusters, with current CAMS projecting an eastward moving MCS from the Bighorn mountains. This suggests a target in the Lusk to Douglas corridor and points south will be the most opportune target for today. As the Day 2 target is Colorado - we are best to position southwards towards WY and leave ourselves in range of the Palmer divide for the next day.

Day 2: A typically Colorado setup with appreciable deep layer shear will evolve on Day 2, with SPC upgrading to a day 2 enhanced over the SE WY, northern-eastern CO region, mostly on the basis of wind and hail risk, but with some tornado risk as well. An approaching central plains SW will yield improving shear toward the later afternoon, with the strongest potential north of the Palmer divide, where 40-50 knots effective shear will yield an environment conducive to supercells. Latest CAMS put and impressive cell tracking east of the DIA region, out toward the KS border, while other runs have favored initiation closer to Limon CO. In either case, CAPE approaching 3000 J/kg and the shear profile with moist upslope flow should yield supercells, potentially growing upscale late in the outlook period.

Day 3: A bifurcated target, with potential both in the eastern KS - NE - IA corridor, and over the central MT area where a new impulse may foster supercells albeit in lower moisture than recent days. The eastern target seems likely to yield at least a few discrete supercells, before upscale growth into one or more convective clusters. The building plains ridge will likely preclude storm development outside these regions.

Day 4 and Beyond: Ridging will likely confine marginal potential to the upper plains, and in the midwest, precluding greater certainty. "

Trying to figure out how we're going to use the camera dome in the F-150:

Team Woodchuck's Forecast: "Looking at current observations, satellite and the 12Z NAM, I like the Casper WY area for relatively early supercell and possible tornado potential in the 20-22Z time frame, and then a second area around Douglas-Lusk WY for a separate set of storms for the 00Z-sunset play.

Logic for Casper: best mid-level flow and low level wind profile yielded by channeling of flow by mountains to south, turning NE winds more easterly in that area. In this type of post-frontal setup, I would normally be bullish on the Chugwater-Wheatland area, but the persistence of northeasterly low level flow suggest that updrafts down that way will rain into their inflow.

Logic for Lusk: Better CAPE feed and mid-level flow should increase towards evening. A possible negative is that according to NAM sounding profles, there could be issues with veer-back-veer as time progresses.

Given the proximity of the two areas, and connectivty via Interstate 25, I think that playing both scenarios should be quite feasible. "

Team Duck's Summary:

"We enjoyed a clear sky sunrise in the cooler air this morning. Post frontal weak upslope flow was expected through northeastern CO and eastern WY, particularly focused in the Cheyenne Ridge to Douglas region, and hence we had a long drive ahead of us. The upslope flow was expected to result in high 40s and perhaps low 50s dew points, destabilising an air mass characterised around about 1000j/kg CAPE. Our expectation was for one or more cells to develop in the area of the Laramie Peak to Douglas area and track somewhat northward, perhaps northeast if a right mover. We headed out early after a good breakfast, and, more importantly, very hot tea.

Storms formed off the high terrain of the Cheyenne Ridge to Douglas Corridor, however the weak instability and low level winds along with anaemic dew points precluded the development of sustained organised storms. While one cell near Wheatland was severe and briefly tornado-warned with tennis ball hail, they generally became clustered or developed along each others’ inflow. We waited for hail to fall from these before crossing the road they hovered over.

Later cells formed toward Casper and Glen Rock, however these failed to avoid clustering, and though while visually attractive, these storms did not provide the tornado opportunity desired.

We retired for the night in Douglas after a delicious dinner in perhaps one of the most unexpected locations for good sushi on the continent."