Forecast and Analysis

Regional Migration Forecast: 28 September – 4 October 2013

Andrew Farnsworth The Cornell Lab Sep 27, 2013

Continental Summary:

The West continues to show a patchwork of locally moderate movements in airspace free of precipitation, and the East gets another pulse of moderate to heavy flights, including in the Southeast and Florida, followed by another strong high pressure center continuing the flights in New England and its immediate vicinity. Birds on the move this week will include Hermit Thrush, Ruby-crowned and Golden-crowned Kinglet, Yellow-rumped Warbler, Swamp, White-throated, and White-crowned Sparrows, and Dark-eyed Junco.



The weekend begins as moderate movements in California and the Desert Southwest stand in strong contrast to the shut down in the Pacific Northwest and Rockies where precipitation is forecast. As the precipitation departs the Rockies and expands in the Pacific Northwest on Saturday and Sunday night, mostly light movements occur in the areas between the two systems in marginal migration conditions.  This pattern continues through the middle of the week, although some more favorable conditions allow heavier movements to occur in the Cascades and northern Rockies. As precipitation finally moves East to end the period, more widespread light to moderate and some locally heavy movements return to the Pacific Coast from Washington South to California. As the precipitation moves East, some portions of the northern and central Rockies have potential to experience fallouts. Birders in these areas should watch inland bodies of water and migrant traps for downed and concentrated migrants on Thursday and Friday next week. Birds on the move this week will include Greater White-fronted Goose, Varied Thrush, Ruby-crowned Kinglet, Wilson’s and Yellow-rumped Warblers, and Golden-crowned Sparrow.

Great Plains

Sandwiched between strong high pressure to the East and an approaching low to the West, the Great Plains begin the weekend with little movement in most areas beyond scattered light flights. As the low passes, moderate to heavy movements follow. The effects are short-lived, as return flow overspreads and shuts down most movements by Monday night. Marginal conditions continue into the middle of the week, with only the northern reaches of the region experiencing conditions that will allow for moderate to heavy movements to occur. Note, however, that areas with light winds in the central and southern Plains may see heavier than expected densities given the timing of the year and a desire to move in many of the migrants passing. A hint of change comes to end the period, as another disturbance enters the region. As it passes, moderate to heavy movements will follow in its wake; additionally, potential for fallouts is reasonable in the Dakotas, as many birds moving South toward the frontal boundary and precipitation will catch up to it and drop out. Birds on the move this week will include Northern Shoveler, Gadwall, Ring-necked Duck, Sedge Wren, Yellow-rumped Warbler, Eastern Meadowlark, and Savannah, Le Conte’s, Swamp, Lincoln’s, Harris’s, White-throated, and White-crowned Sparrows.

Upper Midwest and Northeast

The high pressure that has dominated of late continues to do so, creating favorable to marginal conditions for moderate to heavy movements East of the Appalachians and in New England and creating marginal to unfavorable conditions to the West.  This pattern contracts and shifts farther East over the course of the weekend, until most areas East of the Appalachians experience mostly light movements in marginal to unfavorable conditions.  Some coastal areas of southern New England may experience isolated higher density movements in northeasterly flow to end the weekend. This northeasterly flow is largely the result of an offshore low forecast to stay offshore as it moves parallel to the coast; birders along the immediate coast should watch its passage closely, as some easterly flow at the coast may bring good seawatching conditions. However, a new frontal boundary crosses the Mississippi by Sunday night, spawning a new array of moderate to heavy movements in light but favorable winds. The system passes quickly East, before joining an offshore low, and moderate to heavy movements will occur from New England South into New York in its wake. Again, as was the case in the previous forecast period, high pressure builds near the region; but this time it is to the South, creating northwesterly flow from New York North and East into New England and spawning continued moderate and locally heavy movements through Thursday night. Note that many of these movements will be trans-Atlantic in nature, and some birds may become entrained and travel across the Atlantic in the departing low pressure system. As the high expands to end the forecast period, conditions for movement across much of the region are unfavorable, and the only light to moderate movements that occur will be in locations with lighter than expected winds. Only in the western Great Lakes is there a chance for moderate to heavy movements, and fallouts, as an approaching low may move far enough East to spawn movements in its wake. Birds on the move this week will include Ruddy Duck, Hermit Thrush, Brown Creeper, Winter Wren, Ruby-crowned Kinglet, Yellow-rumped Warbler, Song, Fox, Swamp, White-throated, and White-crowned Sparrows, and Dark-eyed Junco.

Gulf Coast and Southeast

The Southeast coastal Plain and adjacent vicinity, including the Florida Panhandle and Peninsula areas, experience favorable conditions for moderate to heavy movements during the weekend, while the rest of the region is mostly uneventful.  Some moderate to heavy movements may occur from central Texas South to end the weekend. However, Monday begins a period of largely unfavorable conditions for the region, continuing through the end of the week. These conditions include southerly flow and precipitation, and will likely keep birds grounded in many areas. A frontal boundary passing through Texas stalls and dies at the coast, and its effects do not depart the region for the remainder of the forecast period. Areas of the region that have lighter than expected winds, even if southerly, will experience scattered light to moderate and isolated heavy movements depending on the extent of the anomalies, given the time of year. Birds on the move this week will include Yellow-bellied Sapsucker, Northern Flicker, Eastern Phoebe, Marsh and House Wrens, Gray Catbird, Ruby-crowned Kinglet, Yellow-rumped, Palm, and Orange-crowned Warblers, and Swamp and Lincoln’s Sparrows.