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.
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
Here is the short time lapse of the shelf cloud approaching me. 4x speed.
Shooting a little time lapse before getting nailed by blowing sand and dirt.