May 30 Marshall and Roberts Counties South Dakota Traverse and Big Stone Counties Minnesota

Some chase days you just have to take a chance.  I knew the odds of this being a cap bust day were very real as for days the models were showing a very warm EML over Minnesota and the eastern Dakotas with a low pressure system moving from Nebraska into eastern North Dakota during the day.  However, if a storm was to breach the cap, it would have been able to go nuts with the instability and directional wind shear at the junction of the low pressure center, attendant warm front, and trailing cold front.  My target for a few days had been the area where ND/SD/MN all meet.

Well, the worst case scenario panned out as the 700mb temps rocketed into the 14C-15C range.  This is what chasers refer to as a nuclear proof cap.  No way storms are going to fire in that environment.  So Eric Whitehill, Lisa Green, Tyler Burg, and myself waited around various points along I29 on the ND or SD side as the warm front lifted well north of Fargo later in the afternoon while we hoped the approaching cold front and 500mb speed max would erode the cap.  It did...just way off to our south near Watertown, SD.  Well, with unidirectional wind fields running parallel to the cold front, that meant there was only one thing left to do.  Shelf it.

Headed south to Sisseton, SD and climbed the ridge on highway 10 into Marshall county to let a bowing quasi LEWP nail me.  At this point I was willing to take whatever I could get after cooking in the heat, humidty and wind all day.

Shooting a little time lapse before getting nailed by blowing sand and dirt.

Here is the short time lapse of the shelf cloud approaching me. 4x speed.

Coming over the top now.  I wasn't too concerned as there wasn't much for debris to blow around and the chances of large hail were pretty low.  Winds hit about 60 mph only so I decided to head back east through Sisseston and head for the Minnesota  border.  The bow was heading for Eric and Lisa who had stayed on the North Dakota side at about 60-70 mph.

Heading straight east on 10 towards Minnesota now.  With the storm vector more north than east, getting out from under the edge looked like it was going to be pretty easy.  South winds were gusting well over 40 mph just in front of the leading edge of the shelf and moving a lot of dirt.

Looking straight south on South Dakota 10.  Pretty impressive whales mouth was churning away.  The rolling motion in these is always cool to see.

Here is something I haven't seen since Mother's Day 2004 in McLeod county Minnesota.  ENOURMOUS churing gustnadoes under the leading edge updrafts of the line which was now filling in.  Make no mistake, these are not tornadoes regardless of the motion at the cloud base.  They are caused by convergent wind fields at the surface and were getting caught in the updraft area of the linear storm.  With 40+ mph winds going from south to north and 50+ mph winds blowing from west to east, of course they are going to spin a little when they collide.  What made these a little different is they were  occuring under the linear updraft and not out in front of the shelf since the  surface gust front had not outrun the shelf yet.  Regardless, they are cool to watch and are not all that dangerous unless you get a bunch of sand and dirt in your eyes.  Taken near Beardsley, MN looking north.

And one more for the "are you really sure you are looking at what you think you are looking at" file.  Is this an embedded supercell with a clear slot RFD cutting into the base?  Nope.  This is a linear updraft with what is likely a dry downburst.  Somewhat similar to the same process as a rear flank downdraft in a supercell,  dry, cool air erodes the back of the linear updraft well infront of the precip area following behind.  These light areas are often visual clues to look for dirt and dust plumes underneath and to right as the same direction the storm is moving.  None seen in this instance so I'm assuming it was not very strong.  The day ended watching a tornado warned cell pass near Chokio, MN at dark.  I took three photos but they weren't worth posting.  With the storm moving north at 50 mph and not looking impressive, I dumped it and headed home.

2011 Chases