PNW Migration Update – 16 May 2013

Current conditions kept the RTX NEXRAD station in precipitation mode all night. That obscures things a bit but if we watch the loops closely we can see birds are still on their northbound journey. Winds were generally favorable at elevation and the velocity plot shows our little buds booking it at over 30 knots up the Willamette Valley. Persistent showers along the Cascades kept the birds contained and we can see a heavy movement along the S-N fetch of the Columbia from Portland to Clatskanie. The coast had spotty migration and north of Gray’s Harbor was shut down.

Aided by the Jet Stream a little trough of low pressure is now asserting itself across the region. The cold front is laden with moisture so we’ll have some rain, but the winds will be out of the SSW. Migration will be opportunistic as the birds pick their way through the rain cells trying to take advantage of the tail winds. The high pressure system to our south is still quite strong and putting up NNW head winds in the southern portions of the Pacific Flyway.

Nationally the bulk of the action was up the Mississippi and Central Flyways with the Ohio River Valley once again just streaming with migrants. The Atlantic Flyway had only spotty migration. As always, consult the accounts by the regional commentators for details. National Reflectivity Composite loop brought to us by Paul Hurtado.

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