[RummyChick]

http://www.nytimes.com/2011/03/17/science/17plume.html?_r=1

Scientists Project Path of Radiation Plume
By WILLIAM J. BROAD
Published: March 16, 2011

A United Nations forecast of the possible movement of the radioactive plume coming from crippled Japanese reactors shows it churning across the Pacific and touching the Aleutian Islands on Thursday before hitting Southern California late Friday.

[justa-hairyape]

Well it is the UN, but late Friday, hey plenty of time to evacuate and shelter in place if it blows /sarc. Kinda doubt it could get across the Pacific to So Cal in three days. My guess would be 3 days just from Aleutians to So Cal.

[Errant]

A United Nations forecast of the possible movement of the radioactive plume

It should greatly dissipate and "one" of the radioactive iodides has a half life of only 8 days.

It'll be weeks and months of continuous movement, if the source isn't stopped, that may some cause problems.