Forecast and Analysis

Regional Migration Forecast: 19 – 26 April 2013

Andrew Farnsworth The Cornell Lab Apr 19, 2013

Continental Summary:

Light to moderate movements continue in the West amidst some scattered mountain precipitation, while the East has moderate to heavy movements and fallout potential interspersed between strong spring storm systems and the marginal to unfavorable conditions that trail them. Birds on the move this week include Warbling Vireo, Gray Catbird, Yellow Warbler, Rose-breasted Grosbeak, and Baltimore Oriole.


Light to moderate movements prevail across most of the region away from the immediate Pacific Northwest and its forecast precipitation to begin the weekend. As this precipitation moves East into the Rockies and inter-mountain West, it may spawn local fallouts or concentrations in appropriate habitat or on bodies of water. Away from area of precipitation, light to moderate movements will continue with primarily light winds in marginal to favorable conditions. Midweek through the end of the forecast period sees the region experience the most widespread light to moderate movements as the entire region is nearly precipitation free with the exception of a passing disturbance through the Rockies. Birds on the move this week will include Wilson’s Phalarope, Western Wood-Pewee and Olive-sided Flycatcher, Swainson’s Thrush, Hermit Warbler, and Western Tanager among many new arrivals.

Great Plains

High pressure begins the weekend, bringing largely unfavorable conditions for migration to the region. However, areas with light winds, including the western Great Plains, may see light to moderate movements just East of the Rockies north to the Canadian border. By Saturday night some southerly flow returns and more moderate and even locally heavy movements become widespread across the region, continuing into the early part of the week. However, a new frontal system arrives by Tuesday midday, creating unfavorable conditions for migration and possible local shorebird and waterbird fallouts in inland lakes and wetlands. However, passerine fallouts appear unlikely given the timing of the system’s arrival. High pressure follows this frontal passage, creating unfavorable winds for widespread movements; but some areas with light winds will likely see light to moderate movements, particularly over Kansas and Nebraska. By the end of the week, a nice new pulse of birds comes into the southern Plains as moderate and locally heavy movements occur in southerly flow; but unfavorable conditions inhibit most movements farther north to the Canadian border to scattered light to moderate movements. Birds on the move this week will include Mississippi Kite, Wilson’s Phalarope, Swainson’s Thrush, Painted and Indigo Buntings, Clay-colored Sparrow, Dickcissel, and Baltimore Oriole among a suite of many new arrivals.

Upper Midwest and Northeast

As a strong storm system approaches, favorable winds for migration will occur in many areas of the region; however, extensive precipitation is forecast, which complicates the situation. In areas that have precipitation at dusk, migrants will likely stay grounded or take off late; in areas without precipitation at dusk, migrants will take off; and in either of these cases, moderate to locally heavy movements begin the weekend. Birders should watch areas where birds take off, because fallouts are possible if these migrants encounter precipitation. Fallouts along the frontal boundary along the coastal plain (primarily) from Virginia north through New England will include passerines and waterbirds alike. High pressure in the wake of this system slows movements dramatically through the remainder of the weekend, but Sunday night sees a return of more widespread movements over the Mississippi and Ohio River valleys in southerly flow and light to moderate movements over areas of the region East of the Appalachians in light winds. Favorable conditions on Monday night bring widespread moderate and locally heavy movements, continuing into Tuesday in more easterly areas. As the next low approaches, Wednesday morning has fallout potential for the Great Lakes and Ohio River valley. The forecast period ends much as it began, with a frontal boundary bisecting the region and creating a complex set of scenarios for bird movements depending on migrants’ positions relative to the boundary between air masses and precipitation. Where and when birds move, expect moderate to locally heavy movements in southerly winds. Birders should once again once stopover habitat and inland lakes for fallouts on Thursday (and possibly Friday) morning, particularly along the Atlantic coastal plain. Note that behind the front, only scattered light and locally moderate movements are likely in marginal and unfavorable winds. Birds on the move this week will include Great Crested Flycatcher, Wood and Swainson’s Thrushes, Gray Catbird, many species of warblers including Yellow, Nashville, Black-throated Blue, Blue-winged, and Black-and-white, Rose-breasted Grosbeak, Orchard and Baltimore Orioles among many new arrivals.

Gulf Coast and Southeast

A strong front continues to push East across the region, creating potential for fallouts along the Alabama and Florida coasts as trans-Gulf migrants arrive in southerly flow. Behind the front, migrants stay where they have fallen out the previous day in largely unfavorable winds. As the front moves East, so does the possibility for fallouts (into the Carolinas and the Florida Peninsula and particularly the Florida Keys); far behind the front, in Texas, moderate to heavy movements begin in light winds. Favorable conditions bring moderate to heavy movements over Texas to begin the week while lesser numbers of birds are aloft over the Southeast, particularly Florida where rain shuts down movements. By Tuesday night and Wednesday, however, a new system moves to the Gulf Coast, creating a new set of fallout conditions from Texas all the way to the Florida Keys. Of particular note is the strong easterly component to the flow over the Gulf of Mexico, which could mean an eastern Caribbean flavor to the Texas and Louisiana coasts in fallouts on Wednesday. Wednesday night and Thursday will see many of these grounded migrants staying put, but high pressure building into the region over Texas and Arkansas will allow moderate to heavy migrant departure on Thursday night. Birds on the move this week will include Mississippi Kite, Yellow-billed Cuckoo, Eastern Wood-Pewee, many warblers including Magnolia, Chestnut-sided, Black-throated Blue, Cape May, Blackpoll, and Bay-breasted, Dickcissel, and Bobolink among many new arrivals.