A little cooler today, then warming through the weekend

October 3, 2019 – A little cooling today then gradually warming to around normal by Saturday. Warmer than normal early next week then returning back to normal by the middle of next week. No precipitation expected through the extended period.

Discussion

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A weak upper through will pass through the Pacific Northwest today bringing a little cooling but any precipitation will remain well north of the forecast area. High pressure returns and amplifies over the west coast Friday and Saturday bringing fair skies and warming with daytime highs reaching right around normal by Saturday. Warming continues on Sunday as high pressure ridge axis shifts over the west coast. Daytime highs warm to a few to several days above normal. Overnight lows warm to a little above normal as well.

Extended Discussion (Monday through Thursday)

The broad upper ridge settling over the West Coast during the weekend will linger into Monday. However, progressive mid- latitude flow eventually ushers the mentioned ridge eastward allowing for a gradual cool down. Valley highs on Monday sit in the upper 80s, locally near 90 degrees, with readings dropping by about 5 to 7 degrees by the middle of the week. This brings numbers closer to typical early October climatology.

While the upper ridge does advance downstream toward the Rockies, details of the offshore Pacific pattern remain more nebulous. A strong upper trough coming out of the Gulf of Alaska is still primed to skirt north of the region, mostly over the Pacific Northwest.

The bigger shift in the guidance is how a closed low across the east-central Pacific is resolved. While initially expected to open up and become absorbed in a full-latitude trough, ensembles show retrogression rather. While subject to change, this would again build heights over the West Coast which could raise temperatures a bit from the current forecast. Next week continues to look dry, albeit with occasional mid/upper clouds moving through.