Hydrologists at the Alaska River Forecast Center say, from the satellite images, it looks like Southcentral Alaska has a big bull’s eye painted on it.
A high pressure system to the east has funneled a tropical mass of wet air across the region like a steady stream of arrows.
Normally it spreads out towards Canada, so the rainfall doesn’t last as long, or pack such a punch.
On Wednesday, Seward saw five to six inches of rain in just nine hours.
“If you put five inches of water on ground that’s fairly saturated, a lot is going to run off,” says Dave Streubel, a hydrologist at the River Forecast Center. “In a large basin, with all that (water) running in a short time period, you’re going to get some very sharp water level rises and hit record levels.”
Streubel says it’s unusual to have so much rain in such a short time. Also, the amount has varied a lot from place to place, which makes it harder to predict where flooding will occur.
The amounts of rain, says Streubel, are not as high as they have been during past floods.
“We’re not getting the overall total that we had in some of the big events of the past over a 24-hour period. But we’re getting rainfall amounts over a six-hour period that are extremely large. It’s just these intensities, over these four, maybe nine-hour time periods, that are causing our rivers just to sky rocket up.”
Streubel says a break in the rain forecasted on Friday will help. But another system carrying more moisture is expected to move in on Saturday. Struebel says this could cause the Lower Kenai River to overrun its banks. Forecasters expect this system to be weaker and are hoping that it will bring only minor flooding to Soldotna.
But this week, some areas of Southcentral have seen what Streubel calls “extreme” amounts of rainfall, as much as an inch an hour.