Cooler, More Seasonable Conditions Due to Pattern Change

 FastCast--Monday, Aug. 12 to Friday, Aug. 16:

A pattern change will bring more seasonable conditions to Western Washington this week. Expect partly to mostly cloudy conditions on Monday and Tuesday, with AM clouds and PM sun on Wednesday. Partly to mostly cloudy conditions will return Thursday and Friday, with potential chances of drizzle near the coast on Monday and a regionwide slight chance of showers late Friday. Temperatures will reach the low to mid 70s on Monday and Tuesday, increasing to the mid to upper 70s on Wednesday. Temperatures return to the low to mid 70s on Thursday, before likely decreasing to the upper 60s to low 70s on Friday. Low temperatures will remain in the mid to upper 50s through Friday.

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Continue reading the full blog below!

After most of summer has been above normal temperature-wise, more seasonable conditions are ahead. Let's take a look at the forecast!

We'll start with the overall pattern, with the European ensemble forecast below.

This forecast, for Monday, shows troughing across the Northwest. With the absence of high pressure ridges, cloudier and cooler conditions will prevail across the Northwest.

We'll take a look at high temperatures next, starting with the NWS NBM forecast for Monday's highs.

On Monday, expect lowland highs in the upper 60s to mid 70s. The coast will reach the low to mid 60s, and the Willamette Valley will reach the mid to upper 70s. Eastern Washington will reach the upper 80s to low 90s.

Next, here's Tuesday's highs.

Tuesday will be similar, or slightly cooler, than Monday, with lowland highs in the upper 60s to low 70s, coastal highs in the low to mid 60s, and Willamette Valley highs in the mid to upper 70s (isolated low 80s). Eastern Washington will cool further, to the low to mid 80s. 

Finally, here's a look at Wednesday, likely the warmest day of the week.

On Wednesday, the lowlands will reach the mid to upper 70s, except the upper 60s to low 70s near the water. The coast will reach the mid to upper 60s, the Willamette Valley will reach the low 80s, and Eastern Washington will reach the low to mid 80s, with isolated highs in the upper 80s.

Additionally, wildfire smoke will continue to be an issue in Eastern Washington. The pattern bringing cooler & cloudier conditions to Western WA pushes surface smoke eastward. Below is the HRRR forecast for surface smoke on Monday morning.

This forecast shows moderate concentrations of surface smoke across Eastern Washington, likely bringing "unhealthy for sensitive groups" to "unhealthy" air quality. 

By the evening, the smoke plume from the Williams Mine Fire will be impacting southern parts of Eastern WA, as seen below.

Notice the large smoke plume from the Williams Mine Fire and smaller plumes from the Pioneer and Ruby Fires in the north-central Cascades. Expect this to bring moderate to heavy concentrations across Eastern Washington, including the Tri-Cities/Walla Walla and the Spokane region, especially from Monday night to Tuesday morning.

Lastly, let's take a look at the general conditions possible over the next couple weeks. We'll look at the NWS Climate Prediction Center outlooks for mid-August.

For August 17-21, these outlooks show a 40-50% probability of below average temperatures, and a 50-60% probability of above average precipitation. This is due to a potential wetter pattern by the end of the week. Stay tuned for more!