It's reasonably certain now that Hurricane Ivan will make landfall along the Gulf Coast. What happens after that is, well, up in the air.

Usually, storms accelerate as they come inland and ride up the coast. They get caught in the prevailing westerlies, or the high-level current of air that steers storms across the country.

But in this case, the jet stream will remain to the north, allowing Ivan to get cut off. As a result, it will stall somewhere near the Tennessee/North Carolina border. Since winds circulate counterclockwise around a low pressure center, they will upslope along the east side of the mountains to the north of the storm center, bringing potentially copious rains.

The other issue is a cold front expected to head south from Canada. If this clears the coast before Ivan's moisture heads too far north, New York may stay dry. However, if the front is close enough, it may act as a conveyor belt to carry tropical moisture into our area. (This is what happened with Frances--the heavy rains we received, as thoroughly discussed already, were not per se part of the core Frances system.)

Overall, it's a situation generating low confidence forecasts for the weekend. The key word for planning is flexible. Many five-day forecasts show downpours all weekend. While I wouldn't plan an all-day outdoor excursion, just how the weekend plays out won't be clear until it's over.