Forecast and Analysis

Regional Migration Forecast: 21-27 September 2013

Andrew Farnsworth The Cornell Lab Sep 20, 2013

Continental Summary:

A pulse of moderate movements occurs midweek in the West, as the East experiences a major frontal passage followed by a building high pressure ridge that facilitate major movements over land and over water. Birds on the move this week will include Yellow-bellied and Red-naped Sapsuckers, Golden-crowned and Ruby-crowned Kinglets, Yellow-rumped Warbler, Swamp, Lincoln’s, White-throated, Golden-crowned, and White-crowned Sparrows, and Dark-eyed Junco.


Primarily light movements will be the norm to begin the period, and these movements will occur increasingly farther East and South as an incursion of precipitation arrives in the Pacific Northwest. This pattern continues to midweek, by which time light movements will be increasingly sparse in many southern and eastern areas. However, a major change begins in the Pacific Northwest with the passage of the rain-producing disturbance, and many areas of the Pacific Coast, and portions of the northern and eastern Rockies, will experience moderate to locally heavy movements on Wednesday and Thursday nights. More marginal conditions prevail following these movements, and light to moderate movements return to end the forecast period, particularly in the northern and eastern Rockies. Birds on the move this week will include Red-naped Sapsucker, Ruby-crowned Kinglet, Yellow-rumped Warbler, and Fox, White-crowned, and Golden-crowned Sparrows.

Great Plains

A blast of moderate to heavy movements kicks off the weekend across the region, as many birds will fly in favorable post-frontal conditions. This will include good conditions for diurnal movements on Saturday, so sky watchers prepare. As high pressure builds, Saturday and Sunday nights are substantially less favorable for movements, with primarily light to locally moderate movements occurring. Note that more favorable conditions arrive in the northern and western Plains by Monday night, as does the threat of precipitation; to the west of the precipitation, moderate to heavy movements will occur, while much lighter movements will be the norm to the East. These movements shift to the South and East by Tuesday night, followed by generally unfavorable conditions in many areas. Light to moderate movements will be the norm for much of the remainder of the period; however, Thursday night sees the arrival of low pressure in the Canadian Prairies, bringing the potential for more favorable conditions for moderate to heavy movements to the Dakotas. The period ends with this low moving East, well North of the region, and moderate to heavy movements will occur in the northern Plains as this happens. Birds on the move this week will include Northern Flicker, Ruby-crowned Kinglet, Orange-crowned and Yellow-rumped Warblers, Eastern Meadowlark, Dark-eyed Junco, and Savannah, Swamp, Lincoln’s, White-throated, White-crowned, and Harris’s Sparrows.

Upper Midwest and Northeast

A strong frontal passage will occur this weekend across the region, bringing favorable conditions for diurnal and nocturnal migration to many areas. Friday night sees moderate to heavy movements in the western Great Lakes, spreading East for Saturday and Saturday night to many areas West of the Appalachians. By Sunday night favorable conditions reach the coast, and many areas from the Ohio River Valley East to the Atlantic Ocean will experience moderate to heavy movements. Some movements associated with this front will be locally heavy, and the forecast for birds to encounter precipitation in many areas as the system passes suggests many opportunities for local fallouts to occur. As high pressure builds and then sits over eastern Canada, conditions for moderate to heavy movements East of the Appalachians continue into Monday night, as more western areas experience mostly unfavorable conditions. By Tuesday, most of the region away from New England experience local light to moderate movements; but New England and some coastal areas just to the South will experience more favorable conditions for moderate to heavy movements. An interesting situation develops for Wednesday, Thursday, and Friday, as a large high pressure ridge sets up over the northeastern US, bringing a return of favorable conditions for much of the region East of the Ohio River drainage. This return of favorable conditions will facilitate moderate to heavy movements in many areas. Farther West, most areas see only light to moderate movements in much less favorable conditions. Birds on the move this week will include Yellow-bellied Sapsucker, Brown Creeper, Winter Wren, Hermit Thrush, Golden-crowned and Ruby-crowned Kinglets, Yellow-rumped and Orange-crowned Warblers, Swamp, Lincoln’s, White-throated, and White-crowned Sparrows, and Dark-eyed Junco.

Gulf Coast and Southeast

Unfavorable conditions are widespread to begin the weekend, but conditions begin to change midway through the weekend. A frontal boundary moves into the Mississippi River valley by Saturday night, spawning heavy movements to its West. By Sunday the front stall and conditions for moderate to heavy movements spread from central Texas North and East into portions of the southern Appalachians. As the front stalls, much of the southeastern coastal plain remains awash in unfavorable conditions. This pattern continues through the middle of the week, when the front finally moves through completely, and movements will be moderate to heavy in many areas outside of Peninsular Florida. Of particular note in the region is the potential for a coastal fallout in North Carolina on Wednesday and Thursday. Birds flying over the water that departed from points father North will encounter poor visibility and highly unfavorable conditions including rain and turbulence; these birds may seek immediate shelter in coastal stopover habitat, so birders should be watchful for migrants coming ashore. Thursday and Friday nights see continued favorable conditions, primarily East of the Mississippi but including Peninsular Florida. Some of the same conditions that may spawn fallouts on the North Carolina coast may also spawn fallouts in southern Peninsular Florida to end the period, particularly on Thursday and Friday. Birds on the move this week will include Sharp-shinned Hawk, Northern Flicker, Peregrine Falcon, American Kestrel, Ruby-crowned Kinglet, House Wren, Gray Catbird, Palm Warbler, and Rose-breasted Grosbeak.

Special Note: trans-Atlantic flights and fallouts

As low pressure intensifies and departs New England on Sunday night, and favorable migration conditions build in behind the disturbance, many birds will be departing for over water flights above the western Atlantic Ocean. Some birds will become entrained in this system and, depending on the system’s speed, will be carried across the ocean into the western Palearctic migration system. Additionally, as favorable conditions for departures over water from New England continue, birds over the western North Atlantic will encounter precipitation, particularly by Wednesday and Thursday, and many migrants will face challenging conditions. Bermuda is positioned to receive some of these migrants, and birders there should be watchful for fallouts, particularly at the end of the week.