Return to more hot, dry valley weather expected

Thursday, Aug. 31, 2000 | 10:38 a.m.

Pundits say if you don't like the weather, wait five minutes and it will change.

That shift may occur as soon as this weekend, when Mexico's monsoon moisture leaves as suddenly as Tuesday night's downpour came into the Las Vegas Valley.

Drier conditions could return for months, according to long-term forecasts drawn up by meteorologists at the National Weather Service, giving local flood control experts time to work on estimated $1.1 billion project to protect residents and businesses from infrequent but intense storms.

The flood control work is expected to take another 20 years to complete.

The return to a drier weather pattern on Friday could signal another round of brown desert plants and tinder-dry forests in the Spring Mountains, which have characterized Southern Nevada's landscape for the past three years.

"We could have a pretty rapid turnaround to a dry trend," Weather Service meteorologist Ron McQueen said late Wednesday after studying several computer models used by forecasters to predict the next trend.

"With strong southwest winds, all of a sudden we are back to extremely dry conditions again," McQueen said.

The U.S. Forest Service has not lifted restrictions on open flames at picnic areas and campgrounds in the Mount Charleston area -- restrictions in place since late July -- since a single thunderstorm does not erase a drought, federal experts said.

Fires have burned in 10 Western states, including Nevada, and could cost federal, state and local governments more than $1.1 billion.

High humidity and scattered showers have given Nevada firefighters a break this week. Only seven were working today battling 2,600 acres in a fire south of Ely. Another 8,000-acre fire that was 80 percent contained northwest of Ely was being ignored.

While the rain is helping firefighting efforts, it will take long, slow, steady rains or heavy winter snows to put a dent in the drought conditions.

Tuesday's rainfall in the valley dashed a 146-day dry spell that was dampened on Aug. 2 when 0.07 of an inch fell at McCarran International Airport, the official measurement station. Tuesday's official rainfall was 0.46 of an inch.

The sudden storms and subsequent flash floods cascading across the valley Tuesday night erupted after two moist weather systems merged, McQueen said.

An area of low pressure lurking off the coast of Baja California moved inland and eastward as the monsoon system from the Gulf of Mexico strengthened and surged north toward Southern Nevada.

That led to heavy downpours across Nevada, Arizona and Southern California, creating an unusually large storm system for late August, McQueen said.

The peak flow in the Las Vegas Wash reached 3 feet deep, Clark County Regional Flood Control District hydrologist Tim Sutko said.

Three erosion-control barriers under construction in the wash were damaged by the floodwaters. The barriers are designed to slow flooding and help restore up to 2,000 acres of wetlands destroyed over the past 20 years by flash flooding and runoff.

The Charleston Underpass filled with water during the flood, an event expected by longtime residents every time it rains. The chronic problem of underpass flooding is a good example of how long and complicated it is to solve the valley's problems with unpredictable, heavy rainfall, Regional Flood Control District spokeswoman Betty Hollister said.

Although work began in April on a $35.2 million project, the largest of its kind so far, it will take two years before not only the underpass stays dry, but also downtown Las Vegas streets, Martin Luther King Boulevard and Colorado Avenue businesses.

To erase the chronic flood zone, three giant box culverts each weighing 20 tons -- equal to 10 average SUVs -- are under construction to capture floodwaters underground between Charleston Boulevard and Sahara Avenue at Interstate 15. The water will be whisked away to a channel under Washington Avenue.

While the massive public works project creates nightmares for motorists driving in the area, the flood protection hidden underground when the 1 1/2-mile storm drain is complete will be worth it, Las Vegas spokeswoman Debbie Hauth said. "And no one will know it is there," she said.

Ironically, as the Regional Flood Control District works with the cities and the county to prevent urban flooding, continuing development changes the path that water takes, holding surprises for not only new residents, but officials as well.