Rain Chances Decrease, Lower Amounts Expected

FastCast—Wednesday, Aug. 9 to Saturday, Aug. 12:

While rain forecasts have been scaled back for most of Western Washington, there is still a chance of rain across the region, mainly from Chehalis northward. Expect a trace to 0.3” of rain in the lowlands, and 0.2-0.5” from Everett northward and on the coast, except up to 0.75” on the far north coast. Temperatures will drop to the low to mid 70s in the lowlands on Wednesday and Thursday, with lows returning to the mid to upper 50s, after days in the 60s. Temperatures will increase as clouds decrease on Friday and Saturday, with lowland highs increasing to the upper 70s to low 80s. Lows will increase back to the upper 50s to low 60s.

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Continue reading the full blog below!

Rain chances have decreased since my last blog post, with forecasts significantly down trending rain amounts across the region, with a couple exceptions. Let’s take a look at the forecast.

Rain is most likely from early Wednesday morning through midday, with isolated showers across the region in the afternoon.

First, below is the European model forecast for total rain through late Thursday.

This forecast shows 0.1-0.3” of rain across the lowlands, with up to 0.5” around Bellingham. The coast will get 0.4-0.8”, most from Ocean Shores northward. Eastern Washington will get a trace to 0.1”, widely scattered around the area.

Next, let’s look at the GFS forecast, also showing rain through late Thursday.

The GFS forecast shows little rain across the entire region, with the entire lowlands getting a trace to 0.1” of rain, and the coast getting 0.1-0.3”. This forecast is an outlier.

Next, we’ll look at higher-resolution forecasts from the NAM and UW models, starting with the NAM.

The NAM shows a trace to 0.2” for most of the lowlands, with isolated higher amounts in a Convergence Zone feature near Everett. This forecast gives the coast 0.3-0.5”, and brings up to 1-2” for the mountains, which is unlikely.

Finally, we’ll look at the UW high-resolution forecast.

This forecast shows 0.05-0.2” in the lowlands, with up to 0.3-0.5” in Whatcom County and along the coast.

Before we switch to temperature forecasts, let’s take a look at the European model ensemble forecast for Seattle.

Notice how most of the ensemble members are gray, which means up to 0.1” of rain. When most ensemble members show one solution, that’s what is most likely to happen.

Let’s finish up by looking at temperatures over the next couple days. Below is the European model forecast for highs on Wednesday.

Expect lowland highs in the low to mid 70s, coastal highs in the low to mid 60s, and highs in Eastern Washington in the mid 80s to mid 90s.

Next, let’s look at highs on Thursday, also from the European model.

Thursday will be another day in the low to mid 70s in the lowlands. The coast will be a bit cooler, in the upper 50s to mid 60s. Eastern Washington will also be cooler, likely in the upper 70s to upper 80s, except in the low 90s in the lower Columbia Basin.

Enjoy the rain (even if it’s just a little) and the cooler temperatures, as extended warm and dry conditions are looking more likely by the end of this week into next week. Stay tuned!