In my last blog post on 8/30, I warned of a “late-season heatwave with offshore flow” that would “dramatically increase fire danger for the Pacific Northwest.” But when I wrote that, never in my wildest dreams did I imagine that we’d see a wind/firestorm the intensity of the one witnessed earlier this month.
I work as a meteorologist for Portland General Electric. Like the California utilities, we have a plan to shut off power to customers as a last resort during high winds/extreme fire danger to prevent trees/branches from falling on energized lines and causing a wildfire. I thought it was prudent that we had this plan, but I didn’t imagine a situation where wind speeds would ever reach the thresholds beyond which we’d activate it.
I closely monitored fire danger throughout the week leading up to the storm. By September 1, there was increasing confidence that this could be a highly dangerous event, and by the 3rd, there was a very real concern that it could be an extraordinary event. We prepared to initiate our first-ever “Public Safety Power Shutoff” over the weekend, and we initiated it Monday as the storm struck as a last resort to protect against any new wildfires.
Between preparing for the Public Safety Power Shutoff, monitoring the storm as it unfolded, and going through the process of restoring power, the first half of September has been an absolute whirlwind for me. Thankfully, things are calming down now, and I’ll have plenty more to blog about in the coming weeks as I do some analysis on this historic storm.
After the firestorm, a ridge of high pressure built over the Pacific Northwest, allowing the smoke to spread throughout the Pacific Northwest. Air quality reached “hazardous” levels over much of the Willamette Valley and Inland Northwest. As bad as Seattle was, it generally stayed in the “very unhealthy” range – worlds better than “hazardous.”
Thankfully, air quality has improved significantly since Thursday due to strong thunderstorms moving through the Willamette Valley and thoroughly mixing the atmosphere. Unfortunately, air quality is still at “unhealthy” or “very unhealthy” levels for much of California due to the wildfires and light winds there.
There are still many, many fires burning across the west. The fires in the Pacific Northwest west of the Cascade crest have seen significant help from the rain, higher humidities, and cooler temperatures. The fires in California and the Interior West, on the other hand, have grown over the past few days due to strengthening southwesterly winds ahead of the system that brought rain to the Pacific NW.
Forecast:
Monday and Tuesday should be fairly uneventful in the weather department, with partly cloudy skies and temperatures near their seasonal averages for this time of the year. BTW, the fall equinox is at 6:30 AM on Tuesday, so enjoy your last “official” days of summer while they are still with us.
But Wednesday, a dramatic pattern change occurs. An “atmospheric river” will slam into the Pacific Northwest, bringing heavy rain to Western Washington and Oregon. This storm would be a strong one for November, let alone September!
Showers will persist in the wake of the storm Thursday and Friday, primarily over Washington. Most models show a storm total of 1-2 inches of rain to the lowlands and 2-5 inches of rain to the mountains with this system.
Given how low rivers are right now, this precipitation won’t be enough to cause any flooding concerns. Still, it may be enough to set daily flow records. For example, the Northwest River Forecast Center shows the Skagit River at Mt. Vernon cresting above its previous daily records for the 25-28th next week.
Because the heaviest rain is expected to be in Washington, I’m not overly concerned about flooding over Western Oregon burn scars at this time, but it bears watching in case the heaviest precipitation trends south in future runs. I’d definitely trade some light debris flows/burn scar flooding for some fire relief though! Our large fuels are still very dry, and these fires will continue to burn as long as they have dry fuel to feed upon.
Models are in good agreement that we’ll see a warming/calming trend Saturday and Sunday, but they disagree on the following week. The European model has stronger ridging and keeps the Pacific NW warmer/drier-than-average, while the GFS (below) has weaker ridging and has the storm track aimed at British Columbia with moderate/strong systems clipping Washington and NW Oregon. I think the European solution is more likely, but I’m definitely rooting for the GFS solution! Bring on the rain… we need it.
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