June 16, 2016

Team Duck Forecast:

"Day 1 Synopsis: As Skip inferred, a building ridge is starting to take hold in the Plains, but residual moisture return to the northern plains in response to recent lee lows and nocturnal LLJs are contributing to a moist and warm airmass all the way to the Dakotas, though this mornings surface analysis only progs dewpoints into the low 60s in South Dakota, and thus significant moistening will need to be mixed down through the day. A low will move toward western SD, providing a potential triple point for storm development. Strong instability is likely, with MLCAPE parcels above 3000 J/kg, and 30-40 knots of effective bulk vertical shear. This weaker shear will likely mean upscale or semi-discrete storms, but as Skip notes, there is greater helicity further east (and greater capping) meaning that a mature storm that survives could become rather potent. SPC guidance today should be taken with a large capsule of ‘Broyles’ unless otherwise noted.

CAMs project widespread initiation across SD, with the 06Z NAM building in a couple of impressive updraft helicity swaths near to Murdo SD, though NAM is perhaps somewhat bullish, with dewpoints around 75, which seem a little high. 10Z HRRR is much more conservative, with no storms developing before 01Z through central SD, and possibly storms further north toward the ND border - moisture is much more pessimistic as well probably contributing to this model difference, with low 60s dewpoints by around 18Z, mixing out to the 50s by 00Z. The area in question tends to be a late day popper in any case.

As a target I would think Murdo is not a bad starting point, but may require drifting slightly further north as observational moisture becomes more clear as does capping/inhibition.

Day 2: Weak-moderate upslope flow will develop over eastern WY, with weak shear over most of the southern half of the state. A glancing SW trough will provide greater impetus towards the Big Horn mountains and along the I25 corridor west of Douglas, with shear to around 30 knots, and improving further north where moisture return will be weaker. Much of the remaining warm sector looks to be capped, meaning this is the most likely play.

Day 3: A stronger lee low on the north edge of the plains ridge will contribute to a heavily capped but strongly unstable airmass in a formidable shear environment from north central MT through central ND. While features are still resolving themselves, provided sufficient moisture is present in the northern plains, and storms can initiate, tornadoes appear certainly possible with any discrete supercells. It appears likely storms will initiate off the high terrain INVOC Lewiston or Great Falls, and track eastwards, before gusting out into a strong propagating MCS. "

Team Woodchuck Forecast:

"1) Bismarck to Fessenden ND corridor. Daylight initiation appears likely, though I am not sure that storms will move far enough northeast to reach backed surface flow before nightfall, limiting tornado prospects

2) Mobridge area. Here, daytime initiation is possible as well, though how likely is anybody’s guess Any cell that does develop there would have tornado potential in the waning daylight as shear ramps up rapidly with surface winds back strongly towards sunset. Low-level convergence and a dry push from the S-SW from the cyclonic circulation east of the Black Hills could aid in initiation. I see this as the more risky of the two option, but with prospects for higher payoff too.

My take: let’s position around 22-23Z east of Lake Oahu near the ND-SD border, expecting to play the former while hoping for the latter of these two options. "

We must be in the right place! Bumped into the Doppler On Wheels crew in Mobridge.

Ed Grubb!

Tim Marshall!

Tim Marshall and Josh Wurman in front of their deployable weather station probes.

Severe clear all afternoon awaiting initiation.

We finally got a pretty supercell right at sunset. The Missouri River prevented us from getting close, but we had a great vantage from atop a hill.

Abbey Road storm chasing style

We stayed until after nightfall watching the lightning before we called. We had a long, tiresome drive back to Fort Pierre that wound up being too much and tried our nerves.