FastCast—Monday, Oct. 10 to Friday, Oct. 14:
After a smoky weekend with bad air quality across much of the lowlands, smoke relief is on the way. A weak system will brush Western Washington on Monday, bringing cooler temperatures, more clouds, and a slight chance of rain Monday night. Highs will drop a bit to the mid 60s to low 70s. Monday will be partly cloudy, and Tuesday will be mostly sunny but only in the mid to upper 60s. Westerly (onshore) flow will push smoke out of Western Washington on Monday and Tuesday, unfortunately bringing areas of degraded AQI to Eastern Washington and parts of the Cascades. Breezy conditions are possible across Western Washington, with gusts of 20-30 mph possible. The strongest winds (gusting up to 30-40 mph) will be in the Salish Sea (also known as the eastern Strait of Juan de Fuca) and Whidbey Island, mainly Monday evening and night. There is a slight chance of rain, likely a trace to 0.15 inches, in an expected weak Convergence Zone that will form between Everett and Tacoma. 0.1-0.25 inches are possible in the mountains and on the coast. A persistent and large high pressure ridge will return to the Pacific Northwest on Wednesday, bringing highs back to the low to mid 70s, with mostly sunny skies and a potential for morning fog/clouds and more surface smoke. Lows through the entire week will be in the upper 40s to low 50s. Stay tuned for more information!
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This weekend was dominated by surface smoke from the 36% contained Bolt Creek Fire, which has burned over 13,000 acres along US-2 from Index to Skykomish. A weak system will brush the region on Monday, pushing surface smoke eastward.
This weak system will bring a slight chance of rain to the region Monday evening, but there are discrepancies in the forecast models regarding how much rain will fall. The more ambitious NAM forecast is below, for rain through Tuesday morning.
The NAM brings 0.1-0.2 inches of rain to the coast and shows a Convergence Zone area of rain between Seattle and Tacoma. The NAM also shows areas of more significant rainfall (near or above 0.5”) in the Cascades. If this verifies, it would be great news for containing the Bolt Creek Fire.
However, the European model (below) is more pessimistic.
The European model shows light rain (up to 0.1”) along the coast. The European model agrees with the NAM on a potential Convergence Zone bringing up to 0.1 inches of rain between Seattle and Tacoma, with an area of up to 0.25” south of Snoqualmie Pass.
Overall, the prospect for decent rain is not good, and we still await our first major rain event of the season.
However, this system will bring cooler temperatures and breezy conditions for some areas. Gusts will reach up to 20-30 mph around Western Washington, with the strongest winds near Whidbey and Camano Islands and Port Townsend, gusting up to 30-40 mph Monday evening.
Temperatures will cool a few degrees from Sunday to Monday, as seen in the NAM forecast below, showing temperature difference from 6 PM Sunday to 6 PM Monday.
In the lowlands, temperatures will be 3-5 degrees cooler than Sunday, with readings up to 10-20 degrees cooler in the Olympics, Cascades, Willamette Valley, and Coast Range.
What will the highs be? The NAM forecast for Monday’s highs is below.
Expect highs in the lowlands to drop to the upper 60s to low 70s. The Willamette Valley’s numbers on this model are a bit too high, but it will reach the mid 70s there. Eastern Washington won’t get the temperature drop, with highs again reaching the upper 70s to mid 80s.
So, while temperatures will drop from Sunday to Monday, we will remain above average in the lowlands for the foreseeable future (average highs are in the low 60s).
By Wednesday, the familiar pattern of a large high pressure ridge will return to the Northwest, as seen in the European model forecast below.
Notice the large ridge over British Columbia and the Pacific Northwest. This will bring another few days of mostly sunny skies, potential morning fog, and another chance of surface smoke, though the smoke outlook is more uncertain.
The large trough (dark purple) over the Midwest will bring the first freeze of the season for many in the Midwest and Northeast this week.
Stay tuned as we continue to wait for our first major rain event, while October 2022 is on pace to be one of the warmest and driest in Seattle history.
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