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Today's setup involved a negatively tilted trough in the N Rockies with great speed and directional shear across WY and MT. Sfc moisture was limited, but similar to yesterday supercells appeared a good bet. I drove from Rapid City to Broadus, MT where a stop for data at the library revealed a bit more complexity than I expected. Good moisture convergence and EHIs were in place across far SE MT, but elevated severe storms were already underway in N WY north of the sfc low and better jet support. Hesitant to drive any further at this point, I decided to wait outside of town and monitor the skies for any significant changes. I saw these unusual KH-type waves and two shear funnels (one dissipating here) beneath a NW-SE line of Cu that was racing NEward. 1442 MDT |
| Outside of some TCu that glaciated and became soft Cbs well to my east, the sky was alarmingly boring. I fired up the radar and became interested in a lone cell ~60mi to my west. It was moving out of the elevated instability in WY into a slightly better environment, so I caved and shot north on HWY 59 to Miles City. On radar the cell had persistent rotation and was racing along at 40kts to the NE. Here's the view ~15mi south of Miles City looking NW at this readily apparent HP supercell. 1620 MDT |  |
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NWS-BYZ reported 4" hail from this supercell about 40min before this shot. Seeing scud this compact and close to the ground is usually a red flag for hail thanks to a relatively cold precip core. 1626 MDT |
| I arrived in Miles City and originally planned
on getting further north, but the supercell was moving so fast that I was
struck by the initial surge of the RFD gust front (<50kt) while stuck
at an intersection to BUS 94. I already could see a cyan colored
precip core bearing down less than a mile from me and began getting very
concerned for my safety. Once traffic finally got moving, I shot
east on BUS 94 and narrowly escaped that spooky hail core*. Here's
a view later on showing the RFD and inflow corridor to my north directly
where one meso was being indicated (note the inflow band on the lower right).
1637 MDT
* I'm glad I didn't hang around Miles City much longer as numerous car windows were shattered by wind driven hail with gusts to 71kts! |
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Still trying to get ahead of this fast moving supercell. 1645 MDT |
| Even on I-94 I had a hard time building distance between me and the storm. I shot this looking NW at an occluding meso and wall cloud just left of dead center (see next photo for better view). Radar still showed good rotation along this forward flank. 1702 MDT |  |
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I got to Terry and raced NW on HWY 253 to get a better view of the meso and wall cloud (above stop sign). There was some good rotation observed here, but it failed to wrap up any tighter. Oh yeah, the town of Terry would soon be blasted by 76kt winds! One semi was blown over on I94 from all this outflow. 1715 MDT |
| I was liking a new lowered updraft base to the NW and it appeared that a small scale LEWP process was underway given the massive RFD surges to its south. Note the stubby inflow tail on the right. 1716 MDT |  |
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Still pulling in inflow. |
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| I was a bit surprised to see this lurking beneath the updraft base and even more so when I noticed rotation. I'm looking SW as this wall cloud is moving directly towards me. It was time to move north out of its way! 1729 MDT |  |
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I moved up the road a bit to get out of the wall cloud's path. No shelter of any sort was available, so I pulled off the road and prepared for my certain demise given the grapefruit size hail and hurricane force wind reports. The wall cloud ended up passing just to my south and was preceded by scattered 2.5 - 2.75" hail falling straight down (out of the vault most likely). My windshield survived this round, but the outflow was still to come. 1740 MDT |
| The outflow hit from the NW with gusts easily beyond 60kts, but miraculously the hail was much smaller in size. While watching the wind and hail, two horses came sprinting out of nowhere and were followed by a mess of bellowing cattle moving south in obvious pain. 1749 MDT |  |
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The supercell was now going linear on radar and I chose not to follow it any further NE. I waited for the precip to let up and then made tracks back south to Spearfish, SD admiring the MT scenery en route. This was my first time chasing in MT and the experience definitely gave me some memories I won't soon forget. |
All
photos © Copyright 2006 Matt Ziebell
