Forecast and Analysis

Regional Migration Forecast: 26 April – 2 May 2013

Andrew Farnsworth The Cornell Lab Apr 26, 2013

Continental Summary:

The West will experience light to moderate movements for the entire period in generally favorable conditions for migration, whereas conditions in the East are forecast to be complex but favorable for moderate to heavy movements in many areas and fallouts along the Gulf Coast. Birds on the move this week include Least Flycatcher, Gray Catbird, Magnolia, Chestnut-sided and Black-throated Blue Warblers, and Baltimore Oriole.


Generally favorable conditions begin the weekend as light to moderate movements will be the norm in many areas across the region. This pattern continues for the forecast period for most parts of the region, with the exception of a disturbance moving through the Pacific Northwest and northern Rockies early in the week. Birds on the move this week include Western Wood-Pewee, Warbling Vireo, Swainson’s Thrush, Yellow Warbler, and Western Tanager.

Great Plains

The weekend sees a pattern of generally light winds across the region establishing for the coming days. Some scattered precipitation is forecast during this period as well. Although winds may be variable in direction, moderate to heavy movements will occur because winds are light. Birders should watch areas where precipitation and migration meet, because local concentrations and fallouts are possible in such conditions. By midweek, more widespread rain will shut down movements in many areas, particularly farther north. However, if rain does not fall, and winds are light, moderate and even locally heavy movements will continue. By the end of the period, however, high pressure builds into the region sufficiently to reduce most movements to light to moderate levels. Birds on the move this week include Eastern Wood-Pewee, Least Flycatcher, Gray Catbird, American Redstart, Orchard and Baltimore Orioles, and Bobolink.

Upper Midwest and Northeast

High pressure dominates to begin the forecast period, and areas to the west of high pressure experience favorable conditions for moderate to locally heavy movements and close by and to the east of high pressure experience much diminished levels of movements. As the high moves East, more favorable conditions move into the region spawning moderate to heavy movements of birds in many areas away from precipitation. As usual, birders should watch for rain where migration is occurring, as fallouts and concentrations are possible. This pattern continues to midweek, when more widespread precipitation will likely keep birds on the ground in many areas. However, away from areas with rain, birds will be aloft. To end the week, a frontal boundary bisects the region, with areas East of the Appalachians experiencing moderate to heavy movements and areas West experiencing migration shut downs in unfavorable conditions. Birds on the move this week include Veery, Least Flycatcher, Gray Catbird, Magnolia and Chestnut-sided Warblers, Rose-breasted Grosbeak, and Baltimore Oriole.

Gulf Coast and Southeast

This is an interesting week in which moderate to heavy movements will be the norm despite a forecast for widely scattered precipitation in many areas. For the beginning of the forecast period, and continuing through to midweek next week, conditions for migration are mostly favorable or marginal, so birds will be aloft where and when precipitation is not falling. Where birds interact with precipitation, birders should watch for local concentrations of birds. These will differ from typical fallout conditions, even if in coastal areas, in that birds will not experience precipitation in conjunction with a frontal passage and its northerly winds and cooler temperatures and, as a result, not reach the levels of exhaustion that they might normally experience in a true fallout associated with a frontal boundary. Birders should watch the distribution of precipitation and migration carefully, and choose their birding locations appropriately and plan to arrive in a timely manner; birds will not stay grounded for very long. However, a more typical frontal passage is forecast for later in the week. Depending on the timing of this system and how quickly it organizes and moves, fallouts are likely, particularly in the western Gulf of Mexico. If the system organizes and moves off the coast earlier on Wednesday night, fallout likelihood may drop significantly, depending in particular on whether birds can depart in rain free atmosphere from Yucatan. If the system does not organize until later on Thursday, and birds do depart from Yucatan, fallouts are much more likely. Birders along the Texas and Louisiana coasts should watch the evolution of this system carefully, after what could be an already interesting week by that time. Birds on the move this week include numerous shorebirds, Yellow-billed and Black-billed Cuckoos, Willow Flycatcher, and numerous warblers among a diverse array of arrivals.