FastCast--Saturday, Oct. 7 to Tuesday, Oct. 10:
After mostly sunny & pleasant days on Thursday and Friday, record-breaking temperatures are ahead for the lowlands on Saturday. Seattle's record of 77° is likely to be broken, with lowland highs in the upper 70s to low 80s (with areas near the water remaining in the low to mid 70s). Mostly sunny conditions will continue on Sunday, with highs dropping to the low to mid 70s. Clouds will return on Monday, with substantial cooling. Highs will drop further to the low to mid 60s, with 0.2-0.4" of rain expected. A stronger weather system is expected on Tuesday, with highs dropping to the upper 50s to low 60s, and 0.4-0.75" of rain likely. Expect overnight lows in the upper 40s to low 50s through Tuesday, and stay tuned for more information on the upcoming pattern change.
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Continue reading the full blog below!
A very warm and potentially record-breaking October day is expected on Saturday, with lowland highs approaching daily records. Let's take a look at the forecast, and the significant cooling expected over the ensuing days.
We'll start with the European model's forecast for highs on Saturday.
On Saturday, expect lowland highs in the upper 70s to low 80s (likely cooler near the water). The Willamette Valley will reach the upper 70s to low 80s, the coast will reach the upper 60s to mid 70s (due to offshore flow), and Eastern Washington will reach the mid to upper 70s.
Scroll to the bottom of the blog to see the power of offshore flow, which brought 80-85° temperatures to the Washington & Oregon coasts...in October!
Next, let's take a look at the GFS forecast, showing highs on Saturday. This forecast often is slightly different from the European model, a good illustration of potential forecast solutions.
The GFS shows a hotter forecast, with the lowlands in the low 80s from Seattle south (isolated mid 80s), and areas from Seattle north in the mid 60s to upper 70s. The GFS shows coastal highs in the mid 60s to mid 70s, Willamette Valley highs in the low to mid 80s, and Eastern Washington's highs in the low 70s to low 80s.
Regardless of exact temperatures, a noticeably hot day is expected for areas west of the Cascades on Saturday. How far above average will Saturday's highs be? Let's take a look at the European model's forecast for temperature departure from average at 2 PM Saturday, seen below.
Temperatures in the lowlands and Willamette Valley will likely be 15-20° above average! That's significant for any time of year, but especially October! Parts of the Coast Range, Cascades, and Cascade foothills could be up to 25° above average.
Let's continue looking at high temperatures for the coming days, as seen below in the European model forecast for Sunday's highs.
On Sunday, expect to notice cooling in the lowlands, with highs dropping to the low to mid 70s. The coast will cool significantly to the upper 50s to mid 60s, with the return of onshore flow. The Willamette Valley will cool to the mid 70s, while Eastern Washington will peak, with highs in the mid 70s to low 80s.
Next, let's take a look at Monday's highs, also from the European model.
Notice major cooling in the lowlands and Willamette Valley on Monday, with highs dropping to the upper 50s to mid 60s. The coast will remain in the upper 50s to low 60s, while a huge contrast will be found by driving across the Cascades. Expect Eastern Washington's highs to remain in the mid 70s to low 80s.
The storm track will return to the Pacific Northwest early next week, with systems on Monday and Tuesday. Let's take a look at expected rainfall, starting with the European EPS forecast through Tuesday night (for some reason, no city values are showing up currently).
The EPS forecast shows 0.5-0.75" for most of the lowlands, with rain shadowing from Everett to the San Juans. The coast and Olympics will get 1-3", with the Cascades getting 0.75-1.5".
We'll compare this to the GFS forecast, also showing total rainfall through Tuesday night.
The GFS forecast shows a similar picture, with 0.5-0.75" for most of the lowlands (with a rain shadow from Whidbey Island to Victoria BC). The coast and Olympics will get 1-3", and the Cascades pick up 0.75-1.5". These forecasts are very similar, but we'll continue watching and comparing over the next few days to see if disagreements develop.
Before we get to Friday's astounding coastal temperatures, let's take a look at the extended forecast for Seattle and Yakima, using the European EPS forecast. We'll start in Seattle, seen below.
In Seattle, expect a hot day on Saturday (highs in the upper 70s-low 80s), with significant cooling to the upper 50s to low 60s for Monday to Thursday. There is a hint of a warmup late next week. Through the extended forecast, highs and lows look to remain above average (except Tuesday & Wednesday's highs).
Let's take a look at the same forecast for Yakima, seen below.
In Yakima, temperatures will be in the 70s through Monday, hottest on Sunday. A cooldown is expected next week, but shorter and to a lesser extent than Seattle. Both forecasts show a potential for another warmup late next week. Yakima's highs and lows will remain above average, except for a brief period to near the middle/end of next week.
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Astounding Coastal Temperatures on Friday!
Friday was a hot day on the Washington & Oregon coasts! Offshore flow (which brings compression and therefore heating of air), brought high temperatures in the upper 70s to mid 80s for areas from Cannon Beach to Forks & La Push! It's relatively rare for the coastal regions to reach the 80°+ mark in summer, but in October!! That is quite rare!
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