WASHINGTON, D.C. -- National Oceanic and Atmospheric Administration hydrologists released their flood assessment yesterday and parts of Oregon and Washington and much of Idaho have a greater than average potential for flooding this spring. The area's greater-than-average snow pack is the primary factor.
NOAA's forecast is based upon hydrology studies that show that some areas in the Pacific Northwest have a snow pack that is as much as 200 percent above normal. In Idaho, for example, the snow pack in places represents up to 100 inches of water. Depending upon the snowmelt rate, severe flooding could affect many areas east of the Cascades and several drainages along the Idaho panhandle into the central part of the state.
The ideal situation is for a gradual warming trend with little precipitation that would allow the snow to melt within the capacity of the region's streams and rivers. Forecasters don't see a high flood threat for drainages west of the Cascade Range, because that area is more efficient in draining runoff than east of the range.
Another area of concern for flooding is along the Red River of the North from Grand Forks, ND, to the Canadian border and Devil's Lake in east central North Dakota. Forecasters believe the Red River will reach up to 46 feet, only eight feet below the record flood levels of 1997. Flood problems will continue at Devil's Lake by surpassing the record levels of 1997.
In contrast to the flooding threat, many areas of the Southwest may see dryer than average conditions during the spring. This may result in water concerns for Southern California, Arizona, New Mexico, southern Utah, West Texas and even Hawaii.
Fortunately for many areas of the Southwest, reservoir storage is above average, which tends to mitigate the affects of dryer conditions. In the Southwest, only Arizona's reservoir capacity is slightly below average. California, Nevada, Utah and New Mexico all have reservoir capacity above average. The effect of the dryer conditions depends on an area's access to that reservoir capacity.
One threat from the anticipated dryer conditions is high wildfire potential. Texas is particularly vulnerable in that regard. Dry conditions have prevailed over the Lone Star State for the past several years, which will intensify the wildfire threat this spring. The governor of Texas has declared fire bans in three-quarters of the state's counties. Already this year one Fire Suppression Grant has been awarded to the State for a wild fire in Comal County.
Much of the nation's spring flood potential is consistent with a La Ni?a pattern. La Ni?a, the climatic opposite of El Ni?o, is characterized by cooler than normal sea-surface temperatures in the tropical eastern Pacific Ocean. These cooler temperatures are driving the weather patterns seen over the winter and will continue to affect weather patterns this spring. A strong La Ni?a is expected to continue at least through July.
The annual spring outlook is compiled from information provided by the National Weather Service's nationwide network of River Forecast Centers and Weather Forecast Offices. NWS hydrologists and meteorologists work with federal, state and local agencies to gather data on snow, streamflow, soil moisture, and river and ice measurements. This data is combined with rainfall data and short and long-term weather forecasts to determine the likelihood of flooding throughout the United States.