This story was originally posted on MyNorthwest.com
The final days of the summer season are here until the fall equinox on Monday, September 22. Days are getting shorter and nights longer.
This time of year, each day is shorter by close to three and a half minutes, a subtle reminder that the winter season is not far away. That fact is why September is National Preparedness Month, the best time to prepare for whatever nature throws at us in the coming months—in advance.
Western Washington’s fall and winter weather often involves heavy rainfall, flooding, and landslides, along with strong, damaging windstorms, and lowland snow and ice. These kinds of adverse weather are the key reason to prepare ahead of time.
The latest seasonal weather outlook reflects that a weak La Niña is set to return for this winter. La Niña is the opposite sibling of El Niño, when the ocean waters in the eastern Pacific Ocean, tropical waters—the waters west of Peru—are cooler than average. El Niño is when those same tropical waters are warmer than average, and that was the case this past winter.
La Niña and El Niño make big adjustments in how the North Pacific storm track behaves. For La Niña, Pacific storms spend more time moving onshore into the Pacific Northwest as opposed to El Niño, when the storm track takes a more consistent path into California and beyond to the east.
El Niño winter seasons for western Washington tend to be warmer than average and lean toward below-average precipitation and a poorer mountain snowpack.
La Niña winters are sharply different. They tend to be cooler and wetter than average, and produce a healthy mountain snowpack. Earlier this decade, there were three straight La Niña winters, quite rare—the winters of 2020-21, 2021-22, and 2022-23. In each of these winters, the mountains received an above-average mountain snowpack, and the western Washington lowlands had snowfall and even freezing rain events impacting life.
Last winter was also a weak La Niña, but the weather pattern did not follow the usual path. What is usually a wet season turned out to be drier than normal, and the mountain snowpack finished below average.
Latest seasonal weather outlook for Pacific Northwest
The latest seasonal weather outlook for the latter part of fall and into winter offers increased odds of cooler than average temperatures and near or above average precipitation—a more typical La Niña weather outcome.
This trend also points to a healthy mountain snowpack by next spring, good news for snow enthusiasts and water and power generation authorities.
The outlook for the first half of fall, though, reflects near or warmer than average temperatures, with the odds tipping toward wetter than usual conditions.
Impacts of La Niña
Ranking El Niño, neutral (around average tropical eastern Pacific sea surface temperatures), and La Niña winters—La Niña is number one for producing lowland snow. Each of the three back-to-back La Niña winters earlier this decade resulted in lowland snow across much of western Washington.
The lowland snow season typically starts in mid-November and extends into March. Snow not only disrupts transportation but also often results in power outages. Many of the top 10 snowiest winters in western Washington have occurred during La Niña winters.
Windstorm preparedness
Now is also the time to get ready for the potential of strong, damaging windstorms, along with flooding and landslides.
The windstorm season usually begins in October. The nation’s strongest non-tropical wind storm for the lower 48 in American history occurred on October 12, 1962–the Columbus Day Storm. Winds in the interior of western Washington topped 100 mph, knocking down thousands of trees, damaging homes and utilities, with power out for over two weeks, and resulting in 46 fatalities.
This region usually gets a strong, widespread damaging wind storm about every 10 years or so. All other strong windstorms are compared to the granddaddy of them all–the Columbus Day Storm.
The last significant wind storm in this area was the Hanukkah Eve Wind Storm of December 2006. This region is way overdue. Perhaps ask this question: What if another Columbus Day-type wind storm struck again? Would you be ready for an extended period of time without power?
Some may point out that the “bomb cyclone” last November was a significant wind storm, and it was. Yet it did not create widespread wind speeds and damage, more limited to the Cascade foothills and extending into parts of the Puget Sound region, along with the outer coastal region. Many other areas had little or no strong winds and resulting wind damage.
Flood season late October
The flood season usually gets rolling in late October and runs through March. Flooding is number one for presidentially declared natural disasters in Washington. Given how warmer global temperatures hold more moisture, any storms that carry a higher volume of moisture can produce heavier rain amounts in the same time period.
It is quite possible these wet storms could dump more rain and result in more significant flooding than in the past. This issue has been the case not only across the country in recent years, but also around the world.
Weather resources
Are you ready for these hazards or perhaps an earthquake too? Now is the time to prepare.
For helpful tips and checklists for your home, car, pets, and more, go to ready.gov or the CDC winter preparedness website.
One key item for your home, business, school, health care facility, or place of worship is a National Oceanic and Atmospheric Administration (NOAA) Weather Radio all-hazards—a lifesaver for the price of a pair of shoes.
Remember, when you are weather aware, you are weather prepared. To help protect you, your family, and your business, get prepared this month during National Preparedness Month, and you will be better prepared for whatever nature produces this fall and winter.
Ted Buehner is the KIRO Newsradio meteorologist. Follow him on X and Bluesky. Read more of his stories here.
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