Thought it was snowy in Denver and Longmont and Fort Collins and the mountains this winter?
Your perception is accurate, says Colorado State University’s Nolan Doesken, but the problem is that Front Range cities got frequent but light, dry snows while the mountains, in general, got excellent powder but with relatively little water content in the snowpack.
The result? Colorado isn’t as wet as it seems. In fact, some areas remain very dry.
Doesken says the state is now moving into the most critical time of the year for statewide water resources. What happens this year depends on snow this month and next and the amount of rain received in April and May, said Doesken, research associate for Colorado State’s atmospheric sciences department and assistant state climatologist at its Colorado Climate Center.
The official 2001 "water year" runs from October 2000 to the end of September. The critical question is whether a drought, a dry year or good precipitation lies ahead. Doesken can only point to the National Weather Service’s Climate Prediction Center, which has announced that Pacific Ocean sea surface temperatures, pressure differences and wind speeds indicate that the recent "La Nina" is ending. The country now faces the "neutral phase" of the El Nino Southern Oscillation. "In general, this means anything can happen," Doesken said. However, it’s an improvement over last year when conditions favored drought, he said. "When predictions are neutral, the Front Range and the Eastern Plains usually get some pretty good (spring) storms." Based on precipitation reports since October 2000, the Eastern plains have been fairly wet, the Front Range is 80 percent of normal when it comes to precipitation and the mountains, except for the San Juans, are running about 80 percent of normal.
Draw a line from the Wyoming-Nebraska border roughly through Fort Morgan, Colorado Springs, Pueblo and Trinidad, Doesken said, and you’ll find the plains to the east have received as much as 200 percent of their average winter precipitation. In most areas, average precipitation is running about 140 percent.
"Actually, we’re not talking about much (moisture), since winter is a dry season east of the mountains, but considering how dry we were last summer, anything in the topsoil is good for grass and wheat," he said.
West of that line, Denver, Longmont, Boulder, Greeley, Loveland and Fort Collins are dryer, with moisture levels about 80 percent of long-term average (based on the period 1961-1990). But the deficit isn’t all that great and midwinter precipitation rarely adds much to the water year’s total anyway, according to Doesken.
"For Front Range cities themselves, we’re just one or two good spring storms from moving above the average mark," he said. The same phenomenon – lots of snow with relatively slight moisture content – gave the mountains good skiing but, with the exception of bountiful precipitation in the San Juans, only about 80 percent of the average water content with less than 70 percent in the South Platte Basin.
One very important area of the state has slipped through the cracks this winter. Head into the urban-forest interface in the foothills (Cripple Creek, Conifer, Evergreen, Idaho Springs, Nederland, Red Feather Lakes), and it’s really dry.
"The upslope (easterly) winds that brought snow to the cities have been too weak to carry moisture high into the eastern foothills, while Pacific storms in the mountains haven’t spilled over, so several of these areas are near or even below 50 percent of normal precipitation," he said. "We’re looking at some very nasty numbers here. With the fires of last season, we’re looking at some tenuous conditions, including the possibility of some wells going dry.
"The good news is that the same zone, from about six to nine thousand feet down the Front Range, gets a sizable amount of its precipitation in the March to May time period." The dry conditions could improve quickly with a few big, slow-moving storms and cold weather during the spring months. Prediction? Not from a climatologist, but there’s the historical record.
"If storms don’t materialize in the next three months, then we could be looking at problems. High fire danger will return and some people with junior water rights will not get much water," Doesken said. "However, assuming a fairly typical spring, we’ll see some widespread rains and snows that will get us back in business."