Before I talk about La Nina winter weather for Portland, Seattle and other northwest places based on the latest information…let’s talk about fall weather in the northwest during a La Nina year.
Image number one here tells us what we need to know. During a La Nina fall, the only places likely to be unusually cool are places like Astoria and Newport, Oregon. Portland, Oregon and Seattle, Washington. And right along the coast in Northern, Central and Southern California.
And in this second image, we’re looking at the precipitation during a La Nina fall (September-Novemeber). And where’s the biggest chunk of the U.S. likely to be extra wet? You can see it in blue: pretty much all of Oregon and Washington. Ahh, that explains our wet October where many northwest cities are about 150% of average rainfall for the month. So, that’s what La Nina years typically mean in fall–and these have played out perfectly in October with an unusually cool and wet month underway.
La Nina 2011: Update On Strength Of This Year’s La Nina & The Impact
- As of mid-October, this is still a weak La Nina
- For the first time with this La Nina episode, a few forecast models are predicting we could end up with a moderate La Nina. If this happens, it increases our chance of ‘significantly above average’ snow pack in the Cascades. It also increases odds that cool & wet weather continues west of the Cascades in Oregon & Washington.
- Also for the first time with this La Nina episode, at least one forecast model is predicting this will become a ‘strong’ La Nina, matching the strength of the 2010-2011 episode. If this happens, odds tilt toward epic snowpack (or close to it) for Cascades ski resorts.
For now, just plan on an unusually wet and cool remainder of fall. And I’ll keep you updated on the developing La Nina of 2011-2012 and its impacts on the northwest!