Salat witnessed a "SpaceX spiral". Three hours earlier (Saturday, April 15th at 0648 UT), SpaceX launched a Falcon 9 rocket from California's Vandenberg Space Force Base. It carried 51 small satellites to Earth-orbit, a mission known as Transporter-7. When the rocket's discarded upper stage passed over Alaska, it vented its unused fuel. A bit of spin turned the harmless cloud into a spectacular spiral.
An all-sky camera at the University of Alaska's Poker Flat Research Range also recorded the phenomenon:
As strange and rare as it appears, the spiral is a routine by-product of SpaceX operations. Similar blue swirls have been seen after many Falcon 9 launches including this one over New Zealand, another over east Africa, and two more above Hawaii. One may be coming soon to a sky near you.