Forecast and Analysis

Regional Migration Forecasts: 7 September – 13 September

Andrew Farnsworth The Cornell Lab Sep 07, 2012

Light and variable winds will facilitate scattered, light migration in many areas through the weekend, with some coastal areas experiencing slightly larger movements. By Sunday night, more favorable winds spread across coastal areas and into the Great Basin, and moderate movements will become more widespread. The Desert Southwest and Four Corners has rain forecast during these periods, likely keeping most migration to a minimum. These patterns continue into the early part of the week, and then conditions become more marginal, in terms of wind direction and continued rain in the Southwest, in most areas. Moderate movements will give way to smaller, more scattered movements by Wednesday; however, areas of eastern Montana south through the Four Corners may see larger movements in precipitation free areas. The end of the forecast period will see moderate flights return in coastal areas, particularly in Washington and Oregon where birders should watch coastal stopover habitat for migrant songbirds pushed toward these areas in Northeasterly winds. Furthermore, southern California may see moderate movements as well, including in areas around the Salton Sea and Colorado River valley where riparian zones and other migrant traps would be worth checking.

Great Plains
Northerly winds from the Dakotas to Oklahoma and Arkansas will facilitate widespread moderate to heavy migration across the region over the weekend.  Birders in the southern Great Plains should watch closely for storms to create fallouts as birds fly into areas of rain. By Monday, as high pressure builds east, southerly flow returns; however, because rain is not forecast, and winds will be reasonably light, locally moderate movements amid scattered light movements will occur.  Southerly winds and warm area continue to build into the region through midweek, suggesting a similar pattern, albeit one of diminishing numbers of birds, will continue.  Border states may see northerly winds with scattered, light precipitation midweek, suggesting birders should keep a watchful eye for fallouts in areas of rain. This pattern holds through the end of the forecast period, with widely scattered light and local moderate and very local heavy movements will continue across the region.

Upper Midwest and Northeast
Warm moist air continues to prevail from Maine through the Ohio River valley, keeping migration primarily light and scattered. However, a change is on the way, with the western Great Lakes and upper Mississippi River valley feeling the effects of a passing cold front and a strong area of low pressure to the north. In areas to the west of this system’s passage, movements will be heavy and locally very heavy. Birders in these areas should watch carefully for landbird and waterbird fallouts, as rain associated with the passing front will put down birds where it passes. As this system moves east to end the weekend and begin the week, favorable winds will overspread much of the region, spawning heavy movements and some locally very heavy movements. These conditions continue through the beginning of the week, gradually becoming more marginal as the system moves into the Atlantic.  By Tuesday, areas east of the Appalachians continue to have favorable conditions with continued moderate and heavy movements, whereas areas to the west of the mountains will experience generally lighter movements. In quiet areas where winds are light, birders should listen flight calls as calling events should be widespread in many areas of the region. By the end of the forecast period, high pressure builds in coastal and offshore areas, bringing southerly winds and greatly diminished movements to the entire region.

Gulf Coast and Southeast
Variable winds and moist air prevail across much of the region, keeping migration to locally light and very locally moderate levels; however, a frontal boundary approaches the western edges of the region this weekend, facilitating moderate and heavy movements in areas of northerly winds. By Sunday and Monday, this strong front moves east off the coast, spawning heavy and locally very heavy movements across the region. Birders in Florida and the Carolinas should watch for fallouts in coastal habitats where rain meet migrating birds. As high pressure moves east into the northern Appalachians on Tuesday, less favorable winds will bring about more moderate movements with locally heavy migration in areas of the Southeast. Note, a noticeable easterly component to the winds beginning on Monday and Tuesday will make for interesting coastal birding the Southeast, especially given the threat of rain beginning early in the week; birders should consider seawatching where possible, and also be mindful to check coastal habitat along the East coast of Florida for evidence of landbirds coming ashore after departing the coast at points farther north.