Utah may endure flooding

With Utah's snowpack nearly 120 percent of normal, one might think the state is in good shape for water this year. Unfortunately, some localities may find themselves with too much of a good thing.

So far, no flooding is forecast. But if rain and snow continue another five days or so, prolonging the runoff and adding to the snowpack accumulation, the stage could be set for floods in a few areas of northern Utah.

That's particularly the case if the snowmelt is delayed so long that it is brought down quickly by 90-degree weather, according to Brian McInerney, hydrologist with the National Weather Service in Salt Lake City.

On Wednesday night and Thursday, rivers throughout Utah were expected to rise "due to a combination of low-level snowmelt and widespread precipitation," McInerney said. "That will basically bring the majority of all rivers up to significant levels, but not reach any flood categories."

In some parts of northern Utah — Cache Valley, and City Creek, Big Cottonwood Creek and Little Cottonwood Creek near Salt Lake City — snowpacks are more than 150 percent of normal, he said.

That by itself wouldn't indicate any great likelihood of flooding. But weather forecasts for the next five days show unsettled conditions, and that is when warmer weather could start.

So far, not much snow has melted. Instead, the storms have augmented it, he said. More snow and a delayed runoff can cause a "higher potential for flooding."

Rivers that should reach flood stage are the Logan and Blacksmith Fork rivers, plus most streams in Cache Valley. When that will happen is uncertain, as it depends on the spring weather, including temperature and precipitation amounts and intensities.

"City Creek is expected to flow at levels near flood stage," he said. "And then Big and Little Cottonwood are expected to flow at high levels."

High flows are predicted for most of the streams and rivers in northern Utah and the western Uinta Mountains, McInerney said.

Three scenarios are possible for the northern Utah area:

• Good: the weather turns dry and warm, and the snowmelt continues in an orderly fashion.

• Bad: the cool, wet spring weather continues past mid-April and "we get closer to the probability that we are going to reach into the 90-degree range of temperature." That makes it likely that the snowmelt will happen so fast the streams and rivers flood.

• Ugly: With snow still abundant and the weather hot, a thunderstorm dumps a lot of rain on some locality, washing out the snowpack and causing flooding.

"It's a wait-and-see game right now," McInerney said.

Meanwhile, the U.S. Natural Resources Conservation Service posted figures showing that as of April 1, Utah's statewide snowpack was nearly 120 percent of normal.

In basin updates from Wednesday, the Service said snowpacks ranged from 129 percent on the Bear River to 66 percent of normal in southeastern Utah.

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E-mail: bau@desnews.com