Tuesday, October 10, 2023

Rain Continues Wednesday, Then Another Warmup

FastCast--Wednesday, Oct. 11 to Saturday, Oct. 14:

Rain will continue across Western Washington on Wednesday, with storm totals across the lowlands ranging from 0.4-1.3", most from Everett southward. Highs on Wednesday will be in the mid to upper 50s, with lows in the low 50s. There is a chance of isolated thunderstorms on the coast and in the South Sound on Wednesday as well. Rain will clear out on Thursday, with morning clouds turning to afternoon sun, with highs in the mid 60s. Clouds, and temperatures, will increase on Friday, with highs likely reaching the upper 60s to low 70s. Lows on Thursday and Friday mornings will be in the mid to upper 40s. Showers will return on Saturday, with highs dropping back to the upper 50s to low 60s. With weather systems nearby and abundant clouds, it is unlikely anyone in Washington or Western Oregon will have a good view of the annular solar eclipse on Saturday.

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Continue reading the full blog below!

Rain will continue to move through Western Washington on Wednesday, but a warmup is likely on Thursday and Friday. Let's take a look at the forecast!

We'll start with the European Ensemble forecast (EPS), showing total rain from Tuesday morning to Wednesday night (some has already fallen).


This forecast, which includes rain that fell on Tuesday, gives a total of 0.5-1.4" from Everett southward, with a broad rain shadow on the N/NE side of the Olympic Peninsula. This forecast gives the coast and mountains 1.2-3", and gives areas from Chehalis southward into the Willamette Valley up to 1-1.5". Eastern Washington will be largely rain shadowed, with most areas outside of Douglas County getting 0.1-0.4".

Let's compare this to the GFS forecast, showing rain from midday Tuesday to Wednesday night.


This forecast includes some rain that has fallen on Tuesday, mainly Tuesday morning. The GFS shows less rain for the lowlands, with storm totals of 0.6-0.9" for areas from Everett to Chehalis, 0.8-1.2" from Chehalis southward, and 1-1.5" for the coast and mountains, except up to 2.5" for the southern Cascades. This forecast also shows less rain in Eastern Washington.

Now, let's take a look at the NAM high-resolution forecast, showing rain from Tuesday night to Wednesday night.


This forecast shows that most remaining precipitation will fall from Olympia southward and on the coast. The lowlands could get an additional 0.1-0.4" in this forecast, with the coast and mountains getting 0.5-1" in heavy showers, and areas from Olympia southward getting 0.5-1.2". One thing to keep in mind is that this forecast tends to overdo mountain precipitation amounts, so amounts of 3-5+" aren't likely in the Cascades & Olympics.

Now, let's take a look at temperatures. There will be a considerable warmup by Friday across Washington.

Let's start with the European model forecast for Wednesday's highs, seen below.


On Wednesday, expect highs west of the Cascades in the upper 50s to low 60s. Eastern Washington will reach the low to mid 50s around Spokane to the low to mid 60s in the Columbia Basin.

Temperatures will begin increasing on Thursday, as seen in the European model forecast below.


On Thursday, expect sunnier conditions with lowland and coastal highs increasing to the low to mid 60s. The Willamette Valley will reach the mid to upper 60s, and Eastern Washington will reach the upper 50s to upper 60s.

Friday will be the warmest day west of the Cascades, as more weather systems and cooler conditions will arrive on Saturday. Below is the European model forecast for Friday's highs.


Friday will be a noticeably warm day in the lowlands (but not even close to last Saturday's warmth). Lowland highs will reach the upper 60s to low 70s, with the Willamette Valley reaching the upper 60s to low 70s, the coast reaching the mid to upper 60s, and Eastern Washington reaching the upper 60s to low 70s.

However, as we'll see in the EPS extended forecast below, the warmth will be very short lived. Below is the EPS 15-day temperature forecast for Seattle.


As you can see, Friday stands out as the only 70°+ day in the next 2 weeks. Temperatures will cool dramatically on Saturday, and will likely remain in the upper 50s to low 60s for the foreseeable future. Low temperatures will remain in the low 50s, but could reach the upper 40s at times. Notice that the trend for Seattle is slightly above average high & low temperatures for the foreseeable future.

Let's compare Seattle's forecast to the EPS forecast for Spokane, seen below.


In Spokane, warmth will be limited to Friday and Saturday, with temperatures cooling next week and beyond. Spokane's highs will be below average for most of this week, but will remain slightly above average from Friday onward. Low temperatures are cooler than Seattle, with readings in the upper 30s possible. Lows in the upper 30s to upper 40s are relatively near average for Spokane, with readings in the mid 40s or higher being above average.

Stay tuned to upcoming blog posts for more information about the weather conditions around the Pacific Northwest for the annular solar eclipse on Saturday.

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