Starting with a larger view, here is a map of predicted wind speeds
Even if this is not a perfect forecast, we see two things. Very strong winds (brownish and white areas) and they are very wide. So, even if the storm shifts a little to the east or west, there will still be strong enough winds (from dark red to white to dark red) to cause power failures and tree damage if this forecast is approximately correct. The area with damaging winds in this forecast is eastern NC, SE VA, Delmarva, and along and east of I-95 from about Baltimore to NYC to Boston.
Now, this is a higher resolution forecast. The center of Irene is at the X. This is at a single point in time so we can see the details.
Now, here is the National Hurricane Center's 5pm path forecast. The outer stippled area is the average statistical error at 72-96-120 hours (which means it gets wider with time because longer-term forecasts are less accurate than shorter term forecasts). I have added arrows based on the latest forecast to show the geographic corridor I expect the center of Irene to pass down.
Not only is the wind a threat, the ground around NYC and surrounding areas is already moisture. On top of that, a foot of rain is forecast to occur with Irene. This will make it even easier for winds to uproot trees.
Regardless, there were people along the Middle Atlantic coast and in New England without power for ten days to two weeks due to Bob. So, if you are in the outlined areas, be thinking -- now -- about how you are going to handle this storm. I have some suggestions here.
And, unless the Secret Service can wrestle Hurricane Irene to the ground, I suspect President Obama will be cutting his vacation on Nantucket a little short.