Forecast and Analysis

Regional Migration Forecast: 24-30 August 2013

Andrew Farnsworth The Cornell Lab Aug 23, 2013

Continental Summary:

Scattered precipitation in many areas mutes otherwise light to locally moderate movements in the West, as much of the East, particularly the Northeast, sees an early weekend movement before waiting for its first big migration pulse at the end of the forecast period. Birds on the move this week will include Green-winged Teal, Short-billed Dowitcher among other shorebirds, Common Nighthawk, Ruby-throated Hummingbird, and a host of songbirds among other species.


Scattered precipitation across the region will keep birds on the ground in many places to begin the weekend, with only light migration occurring in portions of the Northwest. These conditions continue through the weekend, though improving slightly in the Northwest and deteriorating rather rapidly in parts of the Southwest. Birders in the Desert Southwest should watch closely as low pressure, southerly flow, and heavy rain associated with what is now Tropical Storm Ivo move across the Mexican border, as this disturbance could bring interesting seabird and waterbird displacements to water bodies in the Southwest. Light to moderate movements are likely in areas where rain does not fall, particularly in more northerly locations. This pattern will stabilize over the remainder of the week, with light to moderate movements occurring West and especially to the Northwest of the Rockies and widely scattered light movements in the Desert Southwest and Rockies. Birds on the move this week will include Northern Pintail, Northern Shoveler, Green-winged Teal, Western, Least, and Stilt Sandpipers, Short-billed Dowitcher, Orange-crowned, Townsend’s, and Wilson’s Warblers, Green-tailed Towhee, and Yellow-headed Blackbird.

Great Plains

Mostly unfavorable southerly flow prevails across the region for the weekend as high pressure establishes farther East and South, keeping movements light to generally to a minimum. Although hints of local light and moderate movements may appear in more northern locations to end the weekend and begin the week, midweek is the period when the unfavorable migration conditions ameliorate slightly, becoming more marginal (though not favorable on any nights) and allowing light to moderate movements to expand especially where winds are calm. Birds on the move this week will include Osprey, Sharp-shinned Hawk, Common Nighthawk, Ruby-throated Hummingbird, Blue-headed Vireo, Ovenbird, Northern Waterthrush, Black-and-white, Nashville, Chestnut-sided, Mourning, and Wilson’s Warblers, and Clay-colored Sparrow.

Upper Midwest and Northeast

High pressure building over the Great Lakes bring favorable conditions for moderate to locally heavy movements from Illinois East through New England to begin the weekend. Friday night will be a good night for listening to nocturnal migration in these areas. As the weekend continues, conditions will become less favorable and movements will diminish in size and extent. By Sunday night only the easternmost land in the region will experience light to moderate movements, with increasingly sparse light migration farther to the west. As high pressure sets up shop off the mid-Atlantic states, the early part of the week will not be favorable for much more than light movements scattered across the region. Some parts of northern New York and New England may experience slightly more favorable conditions that allow for heavier movements to occur. A passing low to end the forecast period will herald the first moderate to heavy movements of the fall season from New England South and West through the Mississippi River valley. Birds on the move this week will include Buff-breasted and Baird’s Sandpipers, Common Nighthawk, Veery, Swainson’s Thrush, Tennessee, Nashville, Magnolia, Chestnut-sided, Black-throated Green, Black-throated Blue, and Wilson’s Warblers, and American Redstart.

Gulf Coast and Southeast

Conditions for migration will be mostly unfavorable or marginal at best for this forecast period for nearly the entire region. With the exception of a late-in-the-period break that will see moderate movements from the Mississippi East into the southern Appalachians, most of the remainder of the week will see scattered and local light movements in southerly and easterly wind and scattered precipitation. Birds on the move this week will include Buff-breasted Sandpiper, Short-billed Dowitcher, Common Nighthawk, Ruby-throated Hummingbird, Eastern Wood-Pewee, Acadian and Yellow-bellied Flycatchers, Eastern Kingbird, Red-eyed Vireo, Tennessee, Chestnut-sided, Canada, Mourning, and Wilson’s Warblers, Northern Waterthrush, and Baltimore Oriole.