Concern about radiation particles being carried across the Pacific and into the western U.S. from Japan has become a popular topic.
Despite assurances that radiation amounts will be very low by the time any of that makes it to the West Coast, the flow in the upper levels of the atmosphere
is setting up to bring whatever is being emitted over Japan during the course of the next week, directly towards the West Coast.
In the short term, most of the radiation that is already in the atmosphere will be carried over the Aleutian Islands of western Alaska. The rest of Alaska should be missed, as the flow abruptly turns to the southeast across the Gulf of Alaska and gets involved in the Low pressure center that is sitting just off the West Coast.
Top map shows the jet stream position (at 300mb or ~ 30,000-ft.) on Saturday 
morning March 19.
The middle map shows the wind speeds and flow at 700mb ~ 10,000-ft., which is more representative of the level at which any radiation in the atmosphere would fall out with precipitation.
Strongest winds point at the far western tip of Aleutians, then turn southeast and decrease considerably before turning eastward into the southern half of California.
The bottom map shows the forecasted jet stream position position by the end of next week, which may be more of a concern as the flow straightens out into more of a direct pipeline from west to east across the Pacific.
Not surprisingly, skiers have already inquired about what this radiation might mean for our weather as we go into Spring. “Does it mean more snow or less snow? Or, will it melt the snow that is already on the ground?”
I don’t really know much about the effects of radiation particles in the at
mosphere. They are not like volcanic eruptions and their particles, which can actually enhance snowfall by adding more ice nuclei to the atmosphere. It is my understanding that radiation particles attach to dust particles that already exist in the air, and then fallout with precipitation, along with the dust particles.
Even if a nuclear cloud did enhance snowfall, would you really want to rush out and ski that?
Technically, it wouldn’t create a Nuclear Winter, since Spring begins Sunday, March 20, 2011 at 5:30 p.m.
A Nuclear Spring, maybe.
Text by Jim Woodmencey, meteorologist
Graphics from IPS Meteostar, LEADS On-Line