December 19, 2021

Forecast: December 19th, 2021

By Preston Donion

Happy Sunday, Dawgs!

We’ve officially hit winter break, with only final grades separating us from being fully at peace with fall quarter. I hope those exams and corresponding grades go well, but if not, perhaps the upcoming weather will help soften the blow a bit!

Today looks to be a pretty typical December day: fairly cool, lacking daylight but abundant in the color gray! We’ll be just about on track for December 19th, with highs in the low to mid 40s before dipping into the mid-30s overnight. After yesterday’s rain, a dry day that’s otherwise similar feels like a win to me! After two straight months of no rain over the summer, it sure feels like we’ve had two straight months of only rain this fall, so we’ll probably be okay skipping the soaking today!

The rain-free end to the weekend is soon to be replaced by a wet week, but that doesn’t necessarily just mean rain! We’ll see a handful of storm systems bring showers each day, with temperatures peaking midweek around 50° before dropping off swiftly into the holiday weekend. Wind is the underlying story here, for two reasons; first, we’ll see some strong southerly gusts upwards of 30mph on Tuesday evening into Wednesday as one system rolls in. Second, and perhaps more intriguingly, a shift in the winds is also responsible for the chilly stretch ahead! The winds are coming from the south currently and bringing relatively warm air, but then could carry bitter cold Arctic air from the interior of British Columbia once a low pressure system pulls air from the north instead. With that cold air mass in place, we would then see our precipitation turn to snow as we reach Christmas Day. This is an essential ingredient for significant snow in Western Washington, and its importance will be on display this week: tomorrow looks quite cool compared to average, and also offers plenty of moisture to work with, but we will see mixed precipitation and primarily rain because temperatures are still too marginal to really support snow accumulation. The key to the snow door lies across the border, so we need to coax it down south if we want Washington painted white! Our next chance is that predicted cold stretch at the end of the week.

 

Like the forecasted high temperatures, our certainty on any weather event also drops off significantly the further out it is, so take this all with a grain of salt. A lot of factors have to align for us to get that idyllic White Christmas in the lowlands, and while the signs are pointing that way right now, we have to be much closer to next Saturday to really say anything confidently. That being said, the longer term outlook for the region suggests we’ll be on the cooler and slightly wetter side of average all the way through to 2022, so we will get a few shots at an exciting snow event. Perhaps our best chance according to the current models is the inter-holiday period, around December 26th to the 30th. This morning’s European model suggests that the Arctic air will have a solid grip over the region at this time, with temperatures dipping into the low 20s and all the way down to 15° in Seattle next Tuesday morning! They’re not calling for a great deal of moisture with those frigid temperatures, but we must remember that a model run nine days out is just a hint of what’s to come, rather than a guarantee. So maybe it is that cold but with moisture, or maybe it’s neither! Only time will tell. And on that note, come back to the Dawgcast as we get closer, because we will be watching this potential excitedly! Have a fantastic Sunday and we’ll be back with more tomorrow!

 

Reach forecaster Preston Donion at theuwdawgcast@uw.edu or on Twitter @PrestonDonion