Could "Isaac" bring the rain we need to make up for the 5" to 8" rainfall deficits in parts of the region? At this point, it's a long shot. However, if you look at a few of the forecast models, it's still a remote possibility.
The storm is forecast to come close to the southern tip of Florida by late Sunday, or early Monday. Steering winds would likely bring the tropical system inland Tuesday, hitting already soaked Florida with more flooding rain.
Before we go any further with this, I must disclose the error rate for a storm track seven days out is around 500 miles. That could mean the storm totally misses us and goes out to sea. Remember Hurricane Irene last August? A similar track to Isaac in the first few days. Then, Irene made a hook and soaked the coast, but brought minimal rainfall to western Virginia.
ISAAC'S POSSIBLE IMPACT ON SOUTHWEST VIRGINIA
The Global Forecast model (GFS) is one of the models that we have looked at over the past day or so. it's the one that has the most optimistic view for those who want a soaking rain.
The model forecasts the rain from the tropical system moving up the spine of the Appalachians starting Wednesday and continuing through late Thursday or early Friday. Based on the model output, we'd be talking heavy, tropical rain. Perhaps 5" or so as it interacts with the mountains.
If this holds true, it would certainly help with the the dry (if not drought) conditions. But may not be as good as it sounds for some areas.
THE DOWN SIDE TO THE RAIN
The problem with heavy rain over generally dry ground is you get a lot of runoff. Try taking a dry sponge and pour a gallon of water on it. A lot of water rolls off before the sponge can soak it up.
The same thing happens with rain that comes in too heavy, and too fast. We'd likely see creeks and streams rise quickly along with poor drainage areas.
HOW SOON WILL WE KNOW THE SPECIFICS?
It's way too early to make any firm plans on Isaac's impact here. However, it's never too early to start preparing either. If plans take you to the Caribbean over the next few days, or to the Florida coast later this weekend, you'll need to keep a close eye on the track. Your vacation plans would likely be impacted, especially if traveling by air or cruise ship.
We should know a bit more by this weekend on how Isaac's track will play out across the south and Mid-Atlantic states. Stay tuned to WDBJ7 and First Alert Weather for the latest updates.