With a strong high pressure system boosting temperatures, snowmelt for the next two weeks will push to the tops of Utah riverbanks - and in some cases, over them.

The Sevier River in southern Utah was at flood stage Wednesday afternoon. Flows are expected to jump along with the area's temperatures.

Forecasts call for the mercury to climb into the upper 80s in Cedar City by week's end and possibly to 100 in St. George. The National Weather Service has issued a flood warning for the Sevier River Valley.

"It's just going to continue to climb," Brian McInerney, a hydrologist for the National Weather Service, said of water levels churning out of the high elevations east of Cedar City. Temperatures may even approach 80 degrees in the high elevations of southern Utah.

By Sunday and Monday, runoff could almost double Wednesday's flows on the Sevier River, threatening cabins, summer homes and agricultural property from Panguitch to Richfield. The high water could stay up at that level for two weeks or more.

"We don't see it coming down for as long as we can see in the forecast," McInerney said.

The Virgin River also could approach flood stage Sunday or Monday at the southern boundary of Zion National Park, where forecasters have issued a flood watch.

"It will be really rippin' at Springdale," McInerney said.

But forecasters are hopeful that the Virgin won't come out of its banks there. Nonetheless, tourists should be alerted to the dangers of high water, McInerney said.

"Visitors should be aware," he said. "You'll die if you go into the narrows."

Further south in St. George, the Virgin could flood in Bloomington, as it did in January, said Dean Cox, director of emergency services for Washington County.

"The river is running quite high," he said.

Bloomington residents saved sandbags from January and are ready to use them. Much of the hard-hit real estate along the Santa Clara River from St. George north to the town of Santa Clara has been buttressed by bank work since the January flooding. Nonetheless, officials are monitoring the riverbanks.

"We're seeing a lot of bank erosion and that is impacting people's property," Cox said.

A flood watch also has been set for Ash Creek, a tributary of the Virgin River near Toquerville, and for Cold Creek near Cedar City.

In northern Utah, areas of concern for flooding include Big and Little Cottonwood creeks, City Creek, the Weber River and Blacksmith Fork.

csmart@sltrib.com