Weds 18 April 2012 – PNW Migration Update

The northern portion of the Pacific Flyway was shut down last night due to widespread precipitation.  I’m sure there are a few ambitious types that shifted northward into these light rains or even between showers.  It’s tough to pick them up through the radar noise of the clouds and rain though.  As this low pressure system moves inland the winds will remain favorably out of the south.  It looks like we will be under cloud cover for the next couple of days.  For the birds it will be the precipitation that will dictate movement then.

In the field: Camassia was dead quite yesterday around noon.  Local listserves are not reporting any new arrivals in the area.  There are some eBird reports of Olive-sided and Hammond Flycatchers, BTG, Wilson’s, Nashville, Yellow, and MacGillvary’s Warblers, Warbling Vireo’s and a Bullock’s Oriole.  New birds are in the area, so check out the urban refuges, these birds will still be around.

Regionally: as stated up front the northern half of the Pacific Flyway is under cloud cover and scattered rain.  The regional composite from Medford shows this quite clearly.  It also shows the birds staging in the Central Valley.  There was moderate to heavy migration from San Diego to Sacramento last night.

Nationally: a couple of weather systems; one coming out of the northern plains and one in the south east, combined with NNW winds across New England set the parameters for migration last night.  From southern Texas, up the Central and  Mississippi Flyways, and into the upper mid-west a really decent set of conditions opened the migration super highway.  Check out the static 850mb plot for the winds and the static national composite for a snapshot of this event.  The animated loop from last night can be view here.  For a more detailed discussion of migration back east check out the NEXRAD Trackers found in the sidebar to the right.