south american trip late tomorrow. hitting the points that we talked about here in the rose garden, trying to allay american fears and reassuring the japanese people, one of our closest allies as the president put it since the close of world war ii, the united states stands behind them to recover and get past this immediate crisis. nbc correspondent miguel am ma ger is in los angeles following new developments. miguel? reporter: martin, good afternoon. some time friday, forecasters predict most likely friday evening, small, and we want to emphasize small, low-level radioactive isotopes will likely reach california. experts say those levels are so low they certainly fall within safe limits. a large network of radio monitors is keeping close tabs on all of this. the environmental protection agency or the epa says they ve got 100 radiation monitors that work 24 hours a day and are spread all across the country,