BNSF Symbol Z-NBYWSP1 is the descendant of Santa Fe's legendary #991 train from Richmond, California to Chicago, Illinois. The letter Z represents an entire class of priority trains, NBY refers to North Bay (San Francisco Bay), and WSP refers to the BNSF intermodal facility at Willow Springs, a Chicago suburb. Interestingly, the North Bay trains often command such priority that they will pass other hot trains going in the same direction.
In Santa Fe terminology, train numbers such as 991 were a combination of origin, priority and destination digits, with 9 signifying Richmond, the second 9 as a priority level (the highest) and 1 signifying Chicago. Similarly, a #188 train would be going from Chicago to Los Angeles, with a priority of 8 (still pretty high). Intermediate points on the system were indicated by numbers 2 through 7.
In this scene, an intense thunderstorm is raining buckets on the eastbound North Bay at Floyd, Missouri. The storm will pass through in an hour and by 15:00 the skies will be almost totally clear. It's all good stuff!