Originally Published: May 1, 2008 10:10 p.m.
Regional climate experts are forecasting a strong chance for hotter-than-average temperatures now through June, which historically also is the driest time of year for the Prescott region.
On the more positive side, they also are anticipating a potentially early and wetter-than-average monsoon this summer, although that is less of a surety.
Scientists at the University of Arizona Cooperative Extension and the Climate Assessment for the Southwest organize periodic online climate briefings, and Wednesday's briefing focused on the upcoming spring.
It is not easy to forecast spring precipitation, but the scientists pointed out that an unusually wet winter already has segued into an extremely dry spring, with a statewide average precipitation lower than 25 percent of normal.
Prescott tied the record for its driest April, at zero precipitation. In March the Sundog site on the northeast side of the city recorded only 0.08 inches, or about 5 percent of the average.
Spring is wildfire season in Arizona, so a forecast for an especially warm spring could increase the potential for wildfires.
"Fire season is starting in earnest, and these dry conditions certainly are not helping," said Mike Crimmins, an Extension scientist. At least one local fire agency already is considering fire-use restrictions.
Long-term forecasts are producing "very high" probabilities for above-average temperatures all the way through July, said Gregg Garfin from the University of Arizona's Institute for the Study of Planet Earth.
However, scientists are reluctant to forecast the monsoon precipitation, which typically begins here as early as late June and ends in September.
"It's a tricky time to forecast, and a major area of
scientific interest to improve forecasts during this time period," Garfin said.
Forecasters in Mexico, with the help of Art Douglas in the U.S., are predicting above-average precipitation for northwest Mexico in June and July, Garfin noted.
That is because La Niña winters tend to enhance the storm track north of Arizona, allowing high pressure to set up over the Four Corners region so monsoon storms can surge north from Mexico into Arizona, Garfin explained.
Early monsoons seem to be more common after La Niña winters, too, said Chris Castro, a climate scientist at the University of Arizona.
But again, forecasters warned how hard it is to forecast monsoon trends in the Southwestern U.S.
Several climatologists engaged in a lively discussion about why most of Arizona experienced such a wet winter while under the influence of a strong La Niña, a general cooling of the Pacific Ocean.
"It was one of the wettest La Niñas we have on record," said Paul Iñiguez of the National Weather Service office in Phoenix.
Prescott recorded above-average precipitation in December, January and February.
The Verde River streamflow was 115 percent of average in January through April, said Tom Pagano of the Natural Resources Conservation District's National Water and Climate Center.