Scattered precipitation across the region this period will add a new dynamic to West, with light to moderate movements featuring Common Nighthawk, Western Wood-Pewee, Eastern Kingbird, Western Tanager, and Lazuli Bunting where precipitation is not falling mostly early in the week in the Southwest and central and southern Rockies, while an early period blast of moderate to heavy movements featuring White-rumped Sandpiper, Common Nighthawk, Willow Flycatcher, Yellow-bellied Flycatcher, Philadelphia Vireo, Tennessee Warbler, and Blackpoll Warbler gets swept aside with the passage of a strong frontal boundary in the middle of the week.
Arrows show wind speed and direction (arrow points in the direction to which wind is blowing) 100 m above ground level. Areas with southerly winds are colored red; northerly winds colored blue. Accumulated precipitation (in 6 hour intervals) is green, outlined by white. Broadly speaking, areas of the map in red will experience conditions that are favorable for migration, and areas where red and green (and red and blue) intersect and overlap may experience migrant concentrations and fallouts as migrants interact with precipitation.
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A weekend of favorable conditions interspersed with precipitation will see moderate to heavy flights across much of the region. By Monday, a frontal boundary arrives and proceeds over the coming days to shut down the whole show with the exception of New England. This unfavorable wave affects the entire region nearly through the end of the period, when pockets of more favorable conditions return to some coastal areas and portions of the Great Lakes and Mississippi River valley.
Dynamism is the word for the first half of the period. Although the region’s peak migration has past, moderate to heavy flights, including inputs of trans-Gulf migrants, are likely. Precipitation is also likely, including precipitation near or over the Gulf of Mexico, creating late season fallout potential for numerous coastal locations. Monday and Tuesday will see the arrival of another frontal boundary into the region, creating migration stoppages to the east; however, favorable conditions persist farther west, where migration will continue. This dichotomy continues for much of the second half of the week, including the forecast for precipitation and the potential for it to interact with arriving late season migrants.
No more for this season — but still a few peaking!
Arriving
No more for this season — but still a few peaking!
Peaking
Species
Begin Arrival
Rapid Influx
Peak
Rapid Depart
Willow Flycatcher
4/26
5/4
5/15
5/26
Yellow-bellied Flycatcher
4/27
5/5
5/15
5/26
Black Tern
4/3
4/14
5/15
-
Bullock's Oriole
4/5
4/16
5/17
-
Common Nighthawk
4/8
4/17
5/18
-
Departing
Species
Begin Arrival
Rapid Influx
Peak
Rapid Depart
Blue-headed Vireo
-
-
4/8
5/15
Western Sandpiper
-
-
4/13
5/15
Bobolink
4/15
4/23
5/4
5/15
Bay-breasted Warbler
4/17
4/25
5/5
5/15
Pectoral Sandpiper
3/9
3/19
4/29
5/16
Least Sandpiper
-
4/23
5/1
5/16
Warbling Vireo
4/2
4/16
5/2
5/16
Common Yellowthroat
4/2
4/18
5/2
5/16
Bank Swallow
3/31
4/16
5/2
5/17
Swainson's Thrush
4/9
4/20
5/3
5/17
Wilson's Phalarope
4/13
4/23
5/5
5/17
Philadelphia Vireo
4/16
4/25
5/5
5/17
Dickcissel
4/13
4/22
5/6
5/17
Chestnut-sided Warbler
4/16
4/25
5/6
5/17
Magnolia Warbler
4/19
4/27
5/6
5/17
Cedar Waxwing
-
-
3/29
5/18
Yellow Warbler
4/13
4/23
5/5
5/18
Blackburnian Warbler
4/12
4/24
5/5
5/18
American Redstart
4/18
4/27
5/6
5/18
Baird's Sandpiper
3/12
3/30
5/3
5/19
Ruddy Turnstone
-
-
4/23
5/20
Spotted Sandpiper
4/10
4/22
5/5
5/20
Least Flycatcher
4/21
4/29
5/9
5/20
Wilson's Warbler
4/22
4/30
5/9
5/20
Stilt Sandpiper
4/6
4/21
5/4
5/21
Eastern Wood-Pewee
4/13
4/26
5/10
5/22
Canada Warbler
4/23
5/1
5/11
5/22
Great Plains
Moderate to heavy flights will be overhead this weekend where precipitation is not falling, as an approaching disturbance brings favorable winds to much of the region. But with the passage of this system comes a period of highly unfavorable conditions to kick off the work week, reducing migration to minimal to locally moderate flights. Despite unsettled weather continuing through the middle of the week, birds will try to move if conditions are anything better than unfavorable given the later date in course of the season; light to moderate flights are likely in these marginal conditions. The end of the week sees a return to southerly flow, with another pulse of moderate to heavy flights for the region.
Several disturbances pass through the region this week, bringing precipitation but also favorable winds in advance of their passages. These favorable winds will bring light to moderate movements where and when precipitation is not falling. This is particularly true for Saturday and Monday nights, where favorable conditions will arc from the Desert Southwest north and east through the Rockies. Some movements may be locally heavy during these movements. For the remainder of the week, most of the migration activity will appears on radar in the Desert Southwest, where light to moderate flights will continue. Note also a late in the week pulse of movements in the northern Rockies and eastern Montana, where moderate movements will occur.
