Cold and snowy this winter? As always, it’s quite the speculation.
I’ve been noticing building expectations for another cold and snowy winter. Not only is Snowmaggedon still fairly fresh in memories, we had a rather cool summer (by my count only one day above 90°, we average 5+ days each summer) and forecasts now are talking about snow this weekend across high terrain over the Western US and Canada. Highs near Pullman and Spokane may struggle to reach mid 40’s this weekend… a ~20° drop from mid-week. Brr! for late September.
But can the recent past and present paint us a good picture of what to expect for the upcoming fall/winter storm season? Most people realize weather forecasting out more than a few days seems to be a total crapshoot. Sorry, weather modeling hasn’t come that far (yet). Here was NOAA’s 90-day outlook as of mid-November last year. As seen below, they were predicting above average temperatures (Reds) last winter.
We all know how last February turned out.
Looking forward, there are some rather significant differences vs. last year at this time that may offer us some clues.
Enter “Blob 2019”
Not that one..
This one..
The next chart (below) illustrates sea surface temperatures, with above normal (reds) and below normal (blues).
In years when the blob was very robust and stubborn (2013-2015), it had a strong influence on temperatures year round, with very warm/hot springs and summers, while resulting in lean snowfall years during winter ski season at the passes.
Skiers can still hold out hope that we’ll see enough autumn storms to churn, mix and essentially breakup the warm concentration of ocean water that could prove detrimental to winter snowpack.
What about El Niño, La Niña or La Nada?
El Niño and La Niña are the warm and cool phases of a recurring climate pattern across the tropical Pacific—the El Niño-Southern Oscillation, or “ENSO” for short. The pattern can shift back and forth irregularly every two to seven years, and each phase triggers predictable disruptions of temperature, precipitation, and winds.
However, weak and strong phases alike haven’t seemed to show the strong influence on PNW weather that they once did. You may ask, didn’t our Snowmageddon event happen during El Nino? Yes it did! NOAA puts odds at 75% we’ll have ‘Neutral’ conditions lasting at least through end of 2019. Neutral years are also referred to among fellow weather nerds as “La Nada”.
So what can we probably count on this winter in the lowlands of Snoqualmie/North Bend vicinity? Well besides rain.. like it or not, gap winds!
By mid-late November, Central and Eastern WA areas (eg Cle Elum, Ellensburg, Wenatchee) begin to consistently dip below freezing at night and a dome of high pressure engulfs the region for much of the winter months. This primes the pump so to speak for offshore storms (low pressure) that brush by to start pulling over that high pressure air east of the mountains in an attempt to find atmospheric balance.
We had several gap wind events last winter, most during January and February. They typically produce persistent easterly gusts between 35-55 mph, with a few of these events bringing gusts much stronger. These winds are not the same breed as the broader more traditional westerly windstorms, which I’ll note have historically occurred more frequently in neutral years.
What else to watch out for this fall and winter?
‘Neutral’ years have historically laid claim to having some of the highest streamflow in our local rivers, i.e. flooding potential.
Major flooding in the Snoqualmie Valley is something we haven’t seen for a while, usually caused by a jet stream originating in the tropical pacific bringing warm heavy rains to our mountains, where melting snowpack can compound the problem.
In summary, during winter months there is arguably some level of predictability in projecting snowfall amounts over mountain areas, but as far as the lowlands and foothills are concerned, there are just too many anomalous weather events (or lack thereof) that can frame our winter season, usually only fully grasped in hindsight.
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