Forecast and Analysis

Regional Migration Forecast: 9-16 August 2013

Andrew Farnsworth The Cornell Lab Aug 09, 2013

Continental Summary

Scattered light and locally moderate movements will occur across the West, while two primarily northeastern pulses of light to moderate and locally heavy movements occur among storm systems in the East.


To begin the weekend, scattered precipitation will keep most birds on the ground from northern California East through the Great Basin and central Rockies, while scattered local light movements will occur around the rest of the region. As precipitation dissipates over the course of the weekend, light movements and scattered local moderate movements begin to spread across the region. By the end of the forecast period on Thursday and Friday light and moderate movements will be widespread in many areas.Birds on the move this week will include Green-winged Teal, Northern Shoveler, Lesser Yellowlegs, Baird’s Sandpiper, Olive-sided, Willow and Pacific-slope Flycatchers, Orange-crowned, Nashville, Townsend’s, Hermit, and Wilson’s Warblers.

Great Plains

Marginal to unfavorable conditions keep migration scattered and light in most areas of the region to begin the forecast period. However, Monday sees the beginning of a change, and light to moderate and locally heavy movements are possible in the northern Plains. Birders in eastern Nebraska and Iowa should watch carefully for shorebird concentrations in areas forecast to receive precipitation. Conditions continue to improve across the northern Plains states on Tuesday and Wednesday nights, as light to moderate and locally heavy movements spread farther South and East. Birders in the central and southern Plains states should watch areas of precipitation to concentrate shorebirds in appropriate habitat. Birds on the move this week will include Mississippi Kite, Black-bellied Plover, Greater and Lesser Yellowlegs, Pectoral and Buff-breasted Sandpipers, Black Tern, Ruby-throated Hummingbird, Olive-sided and Alder Flycatchers, Yellow Warbler, and Baltimore Oriole.

Upper Midwest and Northeast

Away from light to moderate movements in the western Great Lakes, much of the region sees precipitation and unfavorable conditions to begin the weekend. However, conditions improve markedly over many areas of the region on Saturday and Sunday nights, when light to moderate movements will be widespread, and will include some locally heavy movements. For those interested in morning flight, Sunday morning would be a good morning to bird along coastal barrier beaches from New Jersey north to Cape Cod. Monday will see a return to much less favorable conditions for much of the region. However, a new pulse of migrants will move on Tuesday and Wednesday nights, beginning in the western Great Lakes on Tuesday and expanding across all but the farther northeastern and southern reaches of the region on Wednesday night. The period ends with a low pressure system moving through the region, creating a complex scenario of precipitation and marginally favorable winds for facilitating migration; light to moderate movements will occur among areas of precipitation and may be concentrated by the storms depending on their extent and severity, so birders should watch radar and note where birds and radar meet to plan appropriate shorebirding. Note that portions of northern New England may experience light to moderate and locally heavy movements on Thursday night in substantially more favorable conditions (i.e. clearer skies, northerly and northwesterly flow). Birds on the move this week will include Blue-winged Teal, Least Bittern, Greater and Lesser Yellowlegs, White-rumped, Least, Semipalmated and Pectoral Sandpipers, Canada and Chestnut-sided Warblers, Bobolink, and Baltimore Oriole.

Gulf Coast and Southeast

With a possible exception of a night or two at the end of the forecast period, this week will see mostly marginal to unfavorable conditions for migration. When precipitation is not falling, and winds are light, light to moderate movements will occur. However, it is likely that these will be local and scattered. Birds on the move this week will include Blue-winged Teal, Black and Forster’s Terns, Common Nighthawk, Ruby-throated Hummingbird, Alder Flycatcher, Barn Swallow, Northern and Louisiana Waterthrushes, and Black-and-white and Yellow Warblers.