Forecast and Analysis

Regional Migration Forecasts: 5 – 12 October 2012

Andrew Farnsworth The Cornell Lab Oct 04, 2012

The West continues to see conditions that favor light to moderate migration, whereas continued pulses of heavy movements occur over much of the rest of the East. Birders should watch carefully in the East for conditions that spawn fallouts and heavy nocturnal calling, as several low pressure centers moving east may produce the northerly winds, low cloud ceiling, and light precipitation combination in many areas.

The pattern of widespread light to moderate migration across region will continue for the forecast period. Generally dry conditions are forecast, but some areas may have widely scattered precipitation that might spawn local fallout conditions. Birders in the Grand Tetons and northern Rockies should monitor the distribution of precipitation this weekend to watch for such conditions. As the week progresses, mountainous parts of California through portions of the Four Corners and the Desert Southwest may experience similar conditions. Additionally, some early week sea-watching may be in order for the central and southern California coasts as westerly and northwesterly winds prevail.

Great Plains
A strong low pressure system moving east over the Great Lakes brings northerly and westerly flow to much of the Plains, and heavy migration will occur over many areas. Birders should listen at night and keep eyes to the sky during the day for the weekend, as many birds will be aloft. As high pressure builds east and then south through the region, migration diminishes to more widespread moderate movements on Sunday night. However, the next low pressure center passes to the north of the region by Monday night, spawning a new wave of heavy movements across northern portions of the region. Farther south, the influence of high pressure keeps more southerly flow active and movements more moderate in scale. These conditions continue into the middle of the week, facilitating more moderate and locally heavy movements, as high pressure sets up shop over the central Mississippi valley. Some day time periods may be quite active for diurnal migrants in northerly and northwesterly winds, so again keep eyes to the sky. As high pressure builds, more southerly influence reappears, and movements diminish in size and scale to primarily scattered moderate migration to end the forecast period.

Upper Midwest and Northeast
A strong low over the Great Lakes spawns widespread moderate and heavy movements across many areas of the region; however, rain will shut down movements in some areas, and create local fallouts where birds meet light rain and low cloud ceilings. These areas may also have higher than typical rates of nocturnal calling, so anyone in areas with high levels of light pollution, cloud cover, and low cloud ceiling will likely experience heavy bouts of flight calling from passing migrants. As this system departs to the east over the course of the weekend, widespread heavy movements continue across the region. Birders along coastlines and ridgelines should watch in the early hours of the weekend for morning flight. As the week begins, more southerly flow moderates movements in all but the Atlantic coastal portions of the region and New England, where heavy movements will continue. By midweek, the pattern of southerly flow moves east, and all but the northern and western most areas around the Great Lakes will see much more widely scattered light to moderate movements. By Wednesday night, as the next low pressure system moves through the region, highly favorable conditions for heavy movements, high bouts of nocturnal calling, and fallouts return as northerly flow and precipitation are forecast. Birders should watch this system closely, as the timing and character of it suggest the potential for large sparrow and kinglet fallouts, among other species.

Gulf Coast and Southeast
Changeable conditions begin the weekend as a disturbance to the northwest and over portions of the Gulf bound the region, with areas free of rain experiencing scattered moderate and locally even heavy movements. As these systems move through and away from the region on Saturday, larger scale moderate and heavy movements will become widespread. In most areas, with light northerly winds prevailing, this pattern continues into Monday. By Monday night high pressure over the mid-Atlantic coast extends far south and west into the region, and moderate to locally heavy movements continue in many areas in light and variable winds. Birders in Florida should watch for coastal movements of seabirds and passerines in Northeasterly flow. This pattern continues through the week until Wednesday night, when low pressure passing to the north brings northerly winds and moderate to heavy migration to much of the region. Texas is forecast for unfavorable conditions, so movements will be greatly diminished in much of the state. Moderate to heavy movements will continue across the region, except Texas, to end the forecast period. N.B. Birders should take note the easterly component to winds for the entire forecast period over the Gulf of Mexico and in Florida. These winds may carry larger than normal numbers of western Atlantic migrants farther west than normal, so keep an eye for larger than typical numbers of Blackpoll Warblers.