Chance of Light Rain, Gradual Warmup Expected

 FastCast—Tuesday, Sep. 12 to Friday, Sep. 15:

A weather system moving through on Tuesday will bring a chance of light rain (up to 0.15”) through Tuesday evening. Highs in the lowlands will be cooler, only in the mid 60s to low 70s. Highs will reach the upper 60s to low 70s on Wednesday, with clouds giving way to sun by the evening. Temperatures will begin an upward trend on Thursday, with highs increasing to the mid to upper 70s. Temperatures will rise further on Friday, with highs reaching the upper 70s to low 80s across the lowlands, hottest from Everett south and away from the water. Throughout the entire period, expect morning lows in the low to mid 50s.

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A weak system will move through the area on Tuesday, with light rain possible. Then, temperatures will slowly begin warming up as we head toward a likely warm weekend (covered in the next blog).

Let’s start with the EPS forecast for total rain through early Wednesday.

This forecast shows 0.05-0.1” of rain for most of the lowlands, except up to 0.2” on the coast and in the mountains.

The NAM high-resolution forecast disagrees, as seen below, showing total rain through Wednesday morning.

This forecast shows 0-0.05” for the lowlands, 0.05-0.25” on the coast, and 0.1-0.4” in the mountains. Either of the shown forecasts is a possibility.

Now for temperatures…let’s take a look at the European model forecast for temperatures on Tuesday.

Expect lowland highs in the mid 60s to low 70s, coastal highs in the low to mid 60s, and Willamette Valley highs in the mid to upper 70s. Eastern Washington will reach the mid 70s to upper 80s.

Temperatures start to slightly increase on Wednesday, seen below.

On Wednesday, expect lowland highs to increase to the upper 60s to mid 70s, coastal highs in the mid to upper 60s, and Willamette Valley highs in the upper 70s to low 80s. Eastern Washington will cool slightly to the mid 70s to mid 80s.

A more significant increase is seen on Thursday, as shown below.

Expect lowland highs to increase to the low 70s to low 80s (mainly near Shelton and from Tacoma south). Willamette Valley highs will skyrocket to the mid to upper 80s, with isolated low 90s possible. The coast will also increase to the upper 60s to mid 70s (low to mid 60s at the beaches), while Eastern Washington increases to the upper 70s to upper 80s (isolated low 90s).

Temperatures will remain warm to hot on Friday and Saturday, with some cooling by Sunday and Monday. Stay tuned for more information in the next post!