SANDPOINT - The National Weather Service is casting doubt on U.S. Army Corps of Engineers projections that Lake Pend Oreille will probably crest 2,066 feet above sea level.

The corps released a table of potential outcomes on Lake Pend Oreille which stated it was "probable" that the lake would top out at 2,066.1 feet, which is 2.6 feet above flood stage.

National Weather Service meteorologist John Livingston said there's only a 25-percent chance that the lake could reach the moderate flood stage level of 2,066 feet.

"In nobody's book is that 'probable.' That's more of a chance, or in our parlance, even a slight chance when we talk about precipitation," said Livingston.

What's more probable, with a confidence level of 75 percent, is that the lake could crest at 2,064.5 feet, which is a foot above flood stage and 2 feet above Lake Pend Oreille's summer pool elevation.

The corps predicts the lake could crest in mid-June, but Livingston said it could happen sooner or later than that depending on weather and runoff conditions.

The lake level was at 2,061.24 feet on Friday afternoon. It's projected to rise to 2,062.16 feet by June 4.

Action stage on Lake Pend Oreille is 2,062.6 feet. Action stage is the point at which water is over the banks, but not flooding manmade structures.

"The lake is going to rise slowly through the next week, but not reach action stage," said Livingston.

The official Lake Pend Oreille flood stage set by the National Weather Service is based on the National Geodetic Vertical Datum of 1929, also known as the Sea Level Datum of 1929. The flood stage is based on lake levels monitored by the corps' gauge in Hope.

However, the Federal Emergency Management Agency recently updated floodplain insurance rate maps for Bonner County using more accurate North American Vertical Datum of 1988.

The difference between the 1929 and 1988 datums vary slightly based on exact locations on the lake, but the average difference in elevation is 3.87 feet.

As a result, those who are monitoring projections put out by the National Weather Service and the corps must add 3.87 feet to get the equivalent elevation on the floodplain insurance rate maps.