A favorable beginning and end of the period for the West sees light to moderate flights of Gadwall, Bufflehead, Long-tailed Duck, Northern Harrier, Bonaparte’s Gull, Hermit Thrush, Chestnut-collared Longspur, and American Tree Sparrow, while a late weekend and late week pulse of moderate to heavy flights in the East feature Hooded Merganser, Common Loon, American Coot, Ring-billed Gull, Snow Bunting, American Tree Sparrow, and Chipping Sparrow.
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Arrows show wind speed and direction (arrow points in the direction to which wind is blowing) 100 m above ground level. Areas with southerly winds are colored red; northerly winds colored blue. Accumulated precipitation (in 6 hour intervals) is green, outlined by white. Broadly speaking, areas of the map in blue will experience conditions that are favorable for migration, and areas where blue and green (and red and blue) intersect and overlap may experience migrant concentrations and fallouts as migrants interact with precipitation.
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A tease of moderate to locally heavy flights grace the eastern reaches of the region to begin the weekend, followed by more extensive but similarly intense flights on Saturday in the Upper Midwest and Sunday farther to the east. These flights continue into Tuesday but become increasingly localized to eastern and coastal areas as the next major disturbance spins toward the Midwest. With this system’s passage on Thursday, moderate to very heavy flights will occur on Thursday night in the Midwest and then farther east on Friday night. Note, this strong low pressure system will be one of the first storms with potential to deposit Ash-throated Flycatcher, Cave Swallow, and other western vagrants in the Northeast.
Scattered moderate flights kick off the weekend as increasingly unfavorable conditions spread across the region. This includes substantial precipitation in Texas, completely shutting down movements there. Sunday night sees a local pulse of moderate to heavy flights in Texas, following the slow departure of the rain. However, not until Wednesday and Thursday nights does the region see more extensive moderate to very heavy flights with the complete departure of low pressure to the east.
A pulse of extensive moderate to heavy flights that kicks off the weekend will become increasingly localized by Sunday night, as favorable conditions on Friday night give way to largely unfavorable conditions on Sunday night. Tuesday and Wednesday nights see another pulse of moderate to heavy, and locally very heavy, flights following the passage of substantial frontal boundary. Following this pulse of birds, the remainder of the week will be relatively quiet as unfavorable southerly flow returns.
The Rockies and the Desert Southwest experience light to moderate movements to kick off the weekend. But flights become increasingly scattered and local for the days that follow until low pressure moves across the Rockies on Tuesday. Following the passage of this low pressure center, eastern portions of the region will see moderate flights, particularly along the eastern front of the Rockies. By week’s end, more extensive favorable conditions build across southern and eastern reaches of the West, spawning more extensive light to moderate flights from California east and north through the northern Rockies.