Rainy, Breezy as Active Weather Pattern Sets In

We have enjoyed a beautiful start to December, with sunny conditions and highs in the upper 50s! However, December will show its true colors this week (and beyond), as an active weather pattern will set in with rain, breezy winds, and lots of clouds.

Tuesday will contain the most rain we’ve received in a couple weeks. Take a look at the UW WRF forecast model, showing precipitation from 4 AM Tuesday to 4 AM Wednesday.

Expect a soggy day, with 0.5-1.3 inches of rain.

There’s a chance of some breezy weather (gusts 15-30 mph) on Tuesday as well.

Wednesday through Friday will be a bit drier, with 0.1-0.4 inches of rain during these three days.

Rain and possible winds return Saturday, when more rain (0.5-2.0 inches) and possible winds (gusts 30-45 mph) are possible. Those details are still uncertain, but stay tuned!

Many signals are pointing to us having above average precipitation through late December. Take a look at the GFS model precipitation forecast through December 24th. (Image via tropicaltidbits.com)

Since this is a long-range forecast (rule of thumb: these aren’t exact) I’d liken it to a “generalization” of our precipitation totals. The model (color key on right) gives the Western Washington lowlands 4-8 inches of rain. Not that far off for this time of year.

Additionally, the NWS Climate Prediction Center calls for a 60-70% chance of above average precipitation from December 15th-21st.

So, what does this mean? More rain is on the way. To prove it...take a look at the 10-day forecast from weather.com for Puyallup. You’re about to see a lot of one icon.

You guessed it...the rain icon. The percentages on the right are the chances of rain. Lots of 50+ percent chances of rain.

Return to Normal Temperatures, Chance of Rain

What a nice end to the week! Highs topped out in the mid-50s on Friday, after another chilly morning, with lows of 28-36 degrees. (Friday’s low temps below).

As we move through the next few days, we will transition from sunny & chilly to our “normal” December weather pattern, with temperatures moderating to near normal. 

However, before we get our first rain of December, winds will accelerate through the gaps in the Cascades as low pressure approaches the coast and higher pressure remains inland. The strong pressure differential across the mountains is outlined in the UW forecast model.

This pressure difference will bring winds gusting 35-55 mph to areas in the foothills near gaps in the mountains (North Bend, Issaquah, Enumclaw).

In addition, we’ll have another chilly morning on Saturday, with low temperatures of 27-36 degrees. Frost, fog, and/or patchy icy spots are possible.

Saturday night and Sunday will bring a chance of rain to the area, with 0.05-0.3 inches of rain expected through early Monday. The UW forecast is below.

More rainy & breezy weather systems are expected through the next week, along with more seasonal temperatures (highs 45-50, lows 35-45).

Cold & Balmy in the Same Day...More Chilly Weather Ahead

Wednesday was a temperature roller coaster! In true Pacific Northwest fashion, we had balmy and freezing temperatures in the same day!

Take a look at Wednesday morning lows around the South Sound.

Brrrr!!! Some spots dropped to the mid-upper 20s.

As the day went on...temperatures warmed substantially, aided by warm downslope flow out of the Cascades. Humidity dropped to 30-50%, and it was quite warm for December! Take a look at the high temperatures below. It was a great day for those who like to be outside!

Wow! Highs of 50-60 degrees...a 20-30 degree increase from the morning!!

Due to a large area of high pressure east of the Cascades, winds accelerated through local gaps in the terrain, producing gusts of 20-40 mph near Enumclaw and North Bend. Areas sheltered from the warming gap winds (also known as Cascadia winds) had cooler temperatures Wednesday morning compared to areas that are exposed to these winds. (low 40s in North Bend vs mid-upper 20s around Puyallup).

Looking ahead...a dissipating frontal system will bring clouds to the area from Thursday through early Friday. 

Due to the clouds, expect temperatures to not be as cold as Wednesday morning, though lows of 30-36 degrees are likely through Friday. After Friday, temperatures moderate some, with a return of rain likely by next week.

Below is the Puyallup forecast from weather.com. (“Tonight” refers to Wednesday night).

One more weather detail to cover...due to relatively light winds and poor mixing of air, the local air quality (called AQI...remember this from September?) has been degraded into the “moderate” category due to a buildup of pollutants such as exhaust and wood smoke.

Moderate AQI means that extremely sensitive people should take caution. This is a very small percentage of the population.

Below is the Puyallup AQI as of Wednesday night, with the AQI forecast as well.

I’d expect any stagnant air to clear out by early next week.