Lower Sugarloaf Fire Makes Its Own Weather By Spawning Rare Pyrocumulus Cloud

As the Lower Sugarloaf Fire balloons in volume within the Okanogan-Wenatchee National Forest west of Entiat, its flames are creating a somewhat unusual phenomenon in the skies overhead.

On Wednesday afternoon, fire officials and weather spotters noted a formation known as a pyrocumulus cloud which had developed above the fire zone.

"Pyrocumulus clouds form when a wildfire is producing intense heat," explains Valerie Thaler with the National Weather Service Office in Spokane. "It's a big wildfire, and when its intense heat is combined with external temperatures which are also hot, it enhances the rising motion of the air surrounding the fire. As that air rises, the available water vapor at higher elevations cools and condenses to form a cloud. So the fire actually makes its own cloud due to this combination of conditions."

Despite the cloud like the one seen Wednesday over the Lower Sugarloaf Fire being moisture-based like most other types of cloud formations, Thaler says a pyrocumulus cloud doesn't produce any precipitation which might aid in minimizing fire activity.

"There does need to be some moisture present to create a pyrocumulus cloud but it isn't the kind of cloud that will produce any rain, so it won't help in reducing any activity related to the fire that actually helped to create it."

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Thaler says although pyrocumulus clouds are not entirely uncommon, the one that formed over the Lower Sugarloaf Fire on Wednesday did climb to an unusually-high altitude.

"This one was up over 40,000 feet, and that's tall. That's at flight level for many aircraft and would have spanned just about all of the troposphere, which is the lower portion of Earth's atmosphere where weather happens."

Thaler says a similar type of cloud formation called a pyrocumulonimbus was also detected over another wildfire on the Okanogan-Wenatchee National Forest earlier this week.

"The Wildcat Fire actually spawned a cloud that was like the one over the Lower Sugarloaf (Fire) on Wednesday, but this one had lightning associated with it. When that happens, it's what's known as a pyrocumulonimbus cloud. These clouds actually make their own thunderstorms which generate lightning."

Given the measured height of the pyrocumulus cloud above the Lower Sugarloaf Fire, Thaler said she wouldn't be surprised to find out that it also generated some of its own lightning.

Thaler adds that the current Red Flag Warning which has been over the fire zone since Tuesday is actually due to the very hot and dry conditions that can cause both pyrocumulus and pyrocumulonimbus clouds to occur, and not any significant sustained winds or wind gusts.

"That's why there's a Red Flag (Warning) out for most of the Cascades (Mountains) right now, because of the dry, hot, and unstable conditions which can produce these types of clouds that can result in rapid blowups of the fire and make the fire spread very rapidly."

The Lower Sugarloaf Fire was ignited by a dry lightning storm that moved over the region late Sunday and was one of two blazes that sparked in close proximity to each other in the same area.

The other fire - dubbed the Loaf Fire, was quickly put out before it could even grow to an acre in size, while the Lower Sugarloaf Fire has more than doubled in size every day over the past four days.

The blaze, which was listed at approximately 2,500 acres late Tuesday, swelled to roughly 3,500 acres by mid-Wednesday, and is currently estimated at 6,222 acres by officials with the Watch Duty wildfire app.

A Red Flag Warning is scheduled to remain in effect through today and fire managers say conditions are not expected to become favorable to minimizing fire activity until sometime this weekend.

The fire is currently uncontained and has prompted numerous evacuation notices for local residents, including a Level 3 notice for some in the Ardenvoir area.