Monday’s pair of destructive wildfires near Philipsburg and Wise River preview a summer that may start earlier and burn hotter than usual.

“We’re forecasting the fire season starting two weeks early, but for southwest Montana we began yesterday,” said Northern Rockies Coordination Center meteorologist Brian Henry. Drought indicators in the region south of Stevensville and Butte already show mid-June dryness, and the country east to Livingston also appears stressed.

“At this time, dead vegetation should still have 20 percent moisture, and we’re already down to 14 percent,” Henry said on Tuesday. “At around 12 percent, we start seeing fires popping up. Fast-forward to yesterday, when you have a fire in Philipsburg that’s gone to 400 acres, and that opened a lot of eyes.”

The Rumsey Gulch fire four miles southeast of Philipsburg destroyed five homes and numerous other structures, and forced evacuation of 20 more on Tuesday. The Pioneer fire five miles west of Wise River has burned about 33 acres near Alder Creek. Both blazes went out of control during Monday’s afternoon and evening thunderstorms before quieting down on Tuesday.

Henry said much of northwestern Montana came into spring with average snowpack levels, after some late-season snows and cool temperatures filled in winter deficits. But the southwest quadrant of the state suffered drought last year and didn’t get much moisture to recover over the winter.

“In last year’s endless fire season, moisture values down there got down to near record-low values,” Henry said. “A lot of the area escaped fire, but the vegetation is already stressed from last year.”

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A new study from the U.S. Geological Survey shows the snowpack declines are accelerating throughout the Rocky Mountains.

“Each year, we looked at temperature and precipitation variations and the amount of water contained within the snowpack as of April,” said USGS scientist Greg Pederson, the lead author of the study. “Snow deficits were consistent throughout the Rockies due to the lack of precipitation during the cool seasons during the 1930s – coinciding with the Dust Bowl era. From 1980 on, warmer spring temperatures melted snowpack throughout the Rockies early, regardless of winter precipitation. The model in turn shows temperature as the major driving factor in snowpack declines over the past 30 years.”

During average years, about 200,000 acres burn in Montana, while light years tally between 60,000 and 80,000 acres. But in the past 15 years, severe fire seasons like 2000, 2003, 2006 and 2012 have recorded more than 1 million acres scorched. The state rarely had a year like that between the first two decades of the 1900s and 1988. Henry said it’s been difficult for firefighters to adapt to the recent tempo.

“There’s no in-between,” he said. “What that shows is the effect of drought and the slightly changing climate we’ve been under. It’s either normal or a barn burner, and we’ve had a really big cluster of bad fire years in the last 12 or 13 years. My concern is this is the new normal.”

But big fires may produce some unexpected benefits. Henry said smoke from big fires appeared to subdue thunderstorms in the same area.

“We had a big plume from the Mustang fire (in Idaho) on a day when the computer models were forecasting lightning,” he said. “And nothing developed in the plume, although storms fired in an arc all around it. It looked like the smoke was changing the environment, although there’s no way to forecast that.”

Reporter Rob Chaney can be reached at 523-5382 or at rchaney@missoulian.com.

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