PNW Migration Update – 20 May 2013

Northbound migrants took to the skies shortly after sunset but only had a couple of hours of uninterrupted flight as a squall line came ashore and pushed inland.  Since this was mostly a widespread band moving ENE the birds that put down were spread out along the storm front and put down about the same time.  There may be a few pockets of concentration mainly to our north.  Winds were mainly out of the WSW so birds were again bunched up along the flanks of the Cascades.  Southern California and the Central Valley had heavy returns so we still have quite a few birds in the pipeline along the Pacific Flyway.

The cold air mass that is being drug out of the arctic is generating precipitable water bringing our current weater – rain.  A look at the Jetstream plot shows the source to be a very organized low in the arctic and it’s interaction with the weaker high out in the Pacific.

The storms continue in Tornado Alley shutting down most of the Central Flyway.  Pockets behind the storm track have continuance migration.  The flight up the Mississippi Flyway was abbreviated as the storm front moved into the Midwest, and the Atlantic Flyway was only active in the northern reaches.  Check out the regional NEXRAD trackers for details.  For a national composite; Paul’s archived loop is here.

Left click for a larger gallery view: