Wildfire activity has exploded across California over the past week, thanks to a record-setting heat wave followed by a rare widespread lightning event. Meanwhile, a trough of low pressure will bring welcome rainfall to Western Washington and British Columbia from Thursday night through Friday.
Wildfire and Smoke Situation
Smoke from major wildfires in California is now impacting Idaho, Wyoming, and Montana. Where I am located in Jackson, the smoke has been very thick over the past two days and the PM 2.5 air quality index has soared to nearly 200, which is considered very unhealthy.
The satellite image below from Thursday afternoon clearly shows the smoke from the California wildfires being transported into the inter-mountain region via west/southwest winds aloft. The worst of the smoke is currently over Southern Idaho, Western Wyoming, and Southwest Montana.
The latest HRRR smoke model (below) in addition to the satellite image (above) shows just how widespread the smoke is across the West.
The fire situation in California has gotten really bad with numerous major fires all across the state. Nearly 771,000 acres have burned in California in the past week alone — a combination of preceding exceptionally hot and dry conditions, followed by a rare widespread thunderstorm outbreak that produced significant lightning.
Farther north, wildfire activity has increased across the Oregon Cascades, Eastern Oregon, and in portions of British Columbia. The Christie Mountain Fire in the Okanagan region of BC near Penticton has burned nearly 5,000 acres (2,000 hectares) and has forced home evacuations.
Beneficial Rain Falling Across Coastal Washington and British Columbia
On the flip side to the fires and smoke impacting much of the West, the Cascades and Coast Mountains of Washington and British Columbia are experiencing beneficial rainfall on Friday. This will help to curb fire danger for most of these coastal areas as well as across the eastern ranges of BC.
Remnant Moisture from Hurricane Genevieve Reaches Northern Rockies Next Week
Former Hurricane Genevieve is weakening as it moves north into the cooler waters of the East Central Pacific, but remnant moisture will work its way inland and rotate into the Northern Rockies around a ridge of high pressure centered across the Central Rockies.
As a result, thunderstorm activity will increase across Idaho, Montana, and Wyoming — particularly the mountainous regions — from Monday through Friday (August 17-21).
Significant rainfall is not expected, but there should be enough moisture to avoid a “dry” thunderstorm outbreak at least. Still, with a mix of wet and dry thunderstorms, there is at least a chance for some new lightning triggered fires as fuel conditions are prime.
A Strong Cold Front Projected for the Weekend of August 29th-30th
Long range models have been consistent in bringing in a trough of low pressure and strong early fall cold front into the Northwest and Northern Rockies next weekend.
This should bring welcome relief not only to the persistent heat, but also a welcome wind shift that should cut off the flow of California smoke to most areas.
The image below shows projected 850-millibar temperature anomalies (in the atmosphere roughly 5,000 ft. above sea level) for next Sunday morning, August 30th. Quite the change if this verifies!
However, it’s not all good news as this is looking like a fairly dry system at this time. The eastern slopes of the Continental Divide in Alberta, Montana, and Wyoming stand the best chance of seeing rain showers (and thunderstorms) over the weekend, while drier and more isolated shower/thunderstorm activity would be the more likely scenario west of the Continental Divide.
Despite the cooler temperatures arriving, we’ll have to watch out for windy conditions in dry areas as this system approaches, which could lead to a spike in fire danger again.
Looking farther out, the cooler temperatures should linger into the first of September, but then a strong ridge of high pressure is expected to build in from the west coast, which would lead to a shift back to above average temperatures from west to east during the first week of September.