Tues 20 Sept 2011

First image is of the winds aloft at 850 mb (approx 5000 ft). The winds up in BC are mixed tonight. Along the coast as a cold front advances there are strong winds out of the south that will keep birds on the ground waiting for the front to pass and take advantage of the north wind in it’s wake.  Inland a bit are some westerly winds that will be pushing birds toward the Central Flyway.  Winds over the PNW are light and variable and pose no impediment to migration but no impetus either.  Bottled up birds that are itching to move will take to the skies.  See the regional composite below.

Second image is of the surface winds and pressure.  Matching the winds aloft in directionality but considerably calmer.

The RTX radar was down last again night.  That’s a full week we’ve been without a look at the local migration picture.  It’s a bit depressing as that is the purpose of this blog — to monitor migration over the Portland area — sigh.

(Click on the thumbnails to view the full-sized images.)

Sunset last night was at 7:14 pm pdst.

Below is a snapshot of the national  and regional pictures.  Note the heavy density of nocturnal flight down the Mississippi Flyway.  Looking back at the 850mb winds you can see that there are strong winds over the plains states and that migration has shifted eastward from last night to avoid those winds.

Regionally there was significant movement to our north and east.