Falling back to warmer weather

Warm weather is expected to linger this week, giving homeowners a little more time to tidy up yards, gardens and homes.

But the warm weather, which is expected to keep highs in the 60s according to the National Weather Service in Reno are bad news for Tahoe ski resorts. Forecasts include sunny and warmer than normal with some clouds moving into the area on Thursday, turning to partly cloudy on Friday.

Additionally, Northern California has had five consecutive wet winters, a string unprecedented this century. A dry one may be due.

"Historically, this is very interesting - five years in a row," said Bill Mork, California state climatologist. "If we get a period of six in a row, we have to go back to the early 1800s to find a period of more wetness."

Before you say, "Whoa, who was out there measuring the snow in 1806?" Mork says the University of Arizona has determined the wetness by looking at tree rings. Who knows how they do it, but that is how officials know.

The "wet" designation is the top of five categories - wet, above normal, normal, dry and critical - and officials determine it now by measuring what flows from four Northern California rivers, including the American.

The "wet" designation may not necessarily correspond to Tahoe's snowpack, but it's a good indicator of the winter precipitation the region gets.

Other indications can be drawn from La Nina, a name given to the global weather pattern when the water around the equator is below normal.

Typically during a La Nina year, Southern California is dryer than normal and the Pacific Northwest, including Oregon and Washington, are wetter than normal. The problem is Tahoe and the rest of Northern California are in between those two areas. The dividing line can fall above or below Tahoe.

Other trends?

Out of the last 10 La Nina winters, there were probably three significant years with major flood events in the region, Mork said. However, the winter of 1975 to 1976 was a La Nina year and also one of the driest winters this century.

La Nina years also have a trend of dumping a lot of snow on this region in November and December, less in the following months. That's by no means guaranteed, though. Last year was a La Nina winter, and the heaviest snow storms didn't happen until January. February was the wettest month.

"(Predicting the weather) is no slam dunk business by any stretch," Mork said.

According to the California Department of Water Resources, which surveys the snowpack at a benchmark location near Echo Summit at Sierra-at-Tahoe, the Tahoe area's snowpack was 146 percent of average in April of 1999; 138 percent in 1998; in 1997, 72 percent; 1996, 110 percent; and in 1995, it was 170 percent, the most of the decade. The year before, 1994, was the worst of the 1990s with 28 percent.

Tahoe's numbers roughly correspond with the statewide averages: 1999, 110 percent; 1998, 160 percent; 1997, 75 percent; 1996, 175 percent; and 1994, 50 percent.

Reno climatologists say don't look for any winterlike conditions until after Friday.