An advancing cold front would set up from east to west along the Wyoming/Montana border, and a lee-side trough with a pronounced dry punch would intersect a low on the cold front, creating a triple-point setup near Sheridan, Wyoming. Regarding the warm sector though, there were some flies in the ointment. Moisture was somewhat scarce, the temp/dewpoint spread was quite large (low 90's over low 50's), and the cap was strong. It appeared little would happen in the warm sector.
However, conditions behind the front were a different story. Moisture was pooling, the temp/dewpoint spreads were more favorable (low 80's over low 60's), and the cap was weaker. These conditions, combined with east surface winds north of the low, created a favorable environment for upslope supercells along the Rocky Mountain Front Range in southeast Montana. Even though I favored the upslope setup, I decided to keep an eye on the warm sector as well and targeted an area in northeast Wyoming from Gillette to Weston on north/south Hwy. 59. This would allow me the option of monitoring the warm sector as the day progressed while still being in position for upslope development to the north. I expected upslope convection to be ongoing by 21z.
While waiting just north of Gillette and watching the convection to my west and northwest, a tornado watch was issued at 12:47 p.m. (all times are in MDT). The first supercell of the day developed near Lame Deer, Montana, and large convective towers began going up to my northwest while the cumulus to my west remained rather flat. I began my trek north on Hwy. 59 at 1:50 p.m. intending to intercept the developing storm to the northwest.
Crossing into Montana at 3 p.m., the updraft base of the cell became apparent to my north and appeared to be either riding along or just north of the small cumulus line that denoted the position of the front. However, the cell was racing to the northeast, and because of the sparse road network, it was going to be quite a task to re-intercept it. Remembering the training supercells Scott Blair, Chris Kridler, Dave Lewison, and I observed on May 28, 2001 (another upslope chase); I stopped just south of Biddle, Montana and let the storm go. To my southwest, a distant area of cirrus was noticeable, but without a cell phone signal, I couldn't access data with my laptop and confirm whether or not the cirrus was a developing anvil. The only thing left to do was wait and hope.
At 3:30 p.m., my patience paid off as an updraft tower became visible under the now large, well-formed anvil. I bumped a bit south and crested a hill, which allowed me my first good view of the entire LP supercell. The anvil was large and crisp; the updraft tower just beginning to show a twist; a long beaver tail fed into the base from the northeast; a few mid-level clouds ahead of the storm elegantly curved around to the north side. It was beautiful!
There was never any doubt as to how to proceed. I found one of the few unobstructed viewing areas in the hilly terrain and setup in the storm's path, watching in awe and shooting time-lapse video for 30 minutes as it rotated toward my location. The cell provided a fantastic show as it approached, morphing from simply a well-structured LP into a stunning, striated exhibit of rotation.
A small area of the storm's base lowered as it now rotated nearly overhead, and the precip. shaft began increasing in intensity. Up to this point, the storm only presented a minimal tornado threat, but with it turning into a classic supercell, the chances of a tornado were increased. At 4:15 p.m., I continued north on Hwy. 59 past Biddle, and took a northeast route on meandering dirt roads in an attempt to stay in a decent position relative to the cell's northeast movement. I was able to stay with the storm for a few minutes, as it continued organizing rapidly with a large, low base and opaque precip. shaft. However, I lost the storm within 30 minutes because of the poor dirt roads and other various obstacles such as having to herd sheep out of the way with my car. I could only watch as the cell kept moving further away while displaying an explosive flanking line and backsheared anvil.
Finally, at 5:20 p.m., I returned to pavement on Hwy. 212 near Boyes. By that time though, the storm was about 20 miles to my north and dying a rapid death. But, I was back in range of a cell phone tower and downloaded some data. Another storm was firing on the front range northwest of Biddle. I immediately went west on Hwy. 212, then back south on Hwy. 59.
Setting up halfway between Biddle and Broadus at 6:43 p.m., the new cell produced what appeared to be a low-hanging wall cloud to my west as the RFD wrapped precip around it. However, the surface winds were now from the northwest, and the cell was being severely undercut. I backtracked north to Broadus and had an excellent view from behind the undercut updraft, which appeared to be more of a shelf cloud at this point. Despite the storm being a mess, there was some astonishing upward and downward motion occurring. I tracked the cell for a couple of miles on a dirt road east out of Broadus, but after having to herd some more sheep out of the way with my car, I decided to let the storm go and call it a day at 7:15 p.m.
Even though the forecasted tornadic event failed to occur, the sheer beauty of the Biddle, Montana LP made this day one of the most enjoyable of my chase vacation. Also, thanks to Dave Lewison for some nowcasting assistance during the latter stages of the chase.