“Hindcasting” is something of great interest to team BirdCast, particularly as a means of improving (eventually) our modeling and thinking about where, when, and how birds appear when and where they do. In this case, let’s look at what happened in the southern Great Plains on Sunday night and Monday morning, 11 and 12 November, respectively. A massive flight of Snow Geese occurred in Missouri, Kansas, and Arkansas last night. Ryan Douglas details the flight here, and Nicholas March details the same flight here. What is presumably this large, regional movement of waterfowl (dominated by Snow Geese!) can be seen in this mosaic animation of weather surveillance radar data (WSR-88D).
An extensive area of rain over the Mississippi River valley gradually moves east. This is a strong low pressure system working its way across the continent that was associated with Winter Storm Brutus. Light to moderate bird migration is visible to the west of the rain, appearing as more uniform, stippled blue patterns. Based on eBird reports and on the ground commentary, the ground-truthing of these bird targets suggests that large scale waterfowl movements are the bulk of these patterns (Snow Geese in particular). Just before local sunrise on 12 November around 6:45-7AM CST, these movements appear on the Kansas City radar near the border of Kansas and Missouri. Other radar stations in the area are also detecting this movement. A particularly strong pulse of birds is apparent from 1300-1400Z, corresponding to 7-8 AM CST, moving Southeast from several radar stations. Notice the position of the cold front, in this case defined by the band of heavy rain associated with its passage. High pressure dominates to the west toward the Rockies, behind the cold front, and the zone where waterfowl are taking flight has highly favorable conditions for migration (e.g. clearing skies, northerly and northwesterly winds). Ryan reports again in the morning on 12 November, when the waterfowl flight is also visible on the regional radar mosaic. Presumably, much of the reflectivity in these radar images represents a massive Snow Goose movement!
This movement was also captured on camera, although you may need to squint!