May 3, 2020 Western Nebraska Supercells

On the morning of May 3, 2020 (an infamous day in May in weather circles), I seemingly didn't have much to do. Due to the COVID-19 pandemic, the Lincoln Diocese had cancelled in-person Mass, so instead of church, I ran a couple errands early that morning and took a hike around Pioneers Park while catching up with my family over the phone. In the back of my mind, I remembered that SPC had a marginal risk for severe storms outlines in western Nebraska and surrounding regions in the High Plains (several hundred miles to the west of Lincoln). Knowing that slow storm motions were likely, and that the tornado risk was quite low (due to a lack of moisture in the post-frontal upslope regime that afternoon), I figured that it could be a relatively low stress first chase to take my girlfriend on. Plus, gas prices were quite low due to the side effects of the pandemic. So after a quick bit of discussion, the chase was on (albeit, with quite low expectations), with an initial target somewhere around Ogallala, NE, where we expected high-based, slowly moving marginally severe supercells.

We left Lincoln around 11:15 and headed west on I-80; initially, we had overcast skies near Lincoln, though skies generally became mostly sunny as we passed to the west of Grand Island (as a sign of the times, we were also doing a Zoom call with my cousins over the car speakers). Once we got west of North Platte, we drove under a high-based cumulus field, which gave way to convective initiation in northeast Colorado and near Lisco, NE (between Ogallala and Scottsbluff). While stopping for gas in Ogallala, our first major decision was whether to drop south into northeast Colorado to chase a cluster of storms which had the potential to merge, or to chase the more discrete (but initially weaker) cell near Lisco (moving slowly southeast to the north of US 26), or to move north into the Sandhills, where the most recent runs of the HRRR showed a comparatively stronger supercell moving southeast out of northwest Nebraska (in an environment which seemed to be slightly more supportive of supercells, too).

We went north towards Lake McConaughy (the instability to the north seemed to be better), and at the last second, I decided that the cell off to the west along US 26 looked stronger and better organized than the one moving towards the Sandhills. We drove to the west (along the north end of the Lake McConaughy settlements), and then went west on US 26, eventually catching up to the supercell drifting southeast towards us.

To my disappointment, it was initially difficult to see much in the way of supercell structure (we had gotten too close to the base, and low clouds had shrouded our view from farther east).

We were way too close initially to see anything other than the storm core.

As we had driven all the way from Lincoln, it only made sense to pursue the storm as it drifted southeast towards Ogallala, to see if the structure would become more interesting. Thankfully, it did.

Weak supercell with flanking line, and a transient wall cloud.

We stopped several times to watch the storm as it drifted southeast towards Lake McConaughy. Once the high-based mesocyclone made it to the lake, our vantage of the structure became quite unique (this was the first time I had watched a supercell with a body of water in the foreground).

As this supercell passed over the lake, another supercell was moving southeast through the Sandhills to our north, and appeared on radar to be strengthening, while the southern cell began to weaken and become elevated above a stabilizing boundary layer to the east. However, due to the hail threat with the Lake McConaughy cell (which at that point was still severe-warned), we chose to drop south to I-80 to position east for the Sandhills cell, rather than intercept the Sandhills cell near Arthur.

During a quick break in Sutherland, the southern cell which we had been chasing rapidly weakened and became very elevated.

Rapidly weakening southern cell from near Sutherland, NE

After our break in Sutherland, we drove north into the Sandhills (my girlfriend's first venture into the Sandhills, as well!) to intercept the northern cell before our road turned to gravel (we never made it to the end of the paved section). Once we made it through the remnant forward flank of the southern cell, an elongated, mostly elevated updraft and wall cloud came into view on the northern cell. At that point, we found a spot to pull off the road, listen to the birds sing in the Sandhills, and enjoy the early evening lighting in the Sandhills while watching both cells weaken as they moved off to the east.

Initial view of northern cell.

Rapidly weakening southern cell, as it raced off to the east, leaving behind a rainbow and a view of the moon.

Northern cell weakening.