Dry Streaks End Tonight!

GOES-16 Low-level Water Vapor showing a strong front coming into the Pacific Northwest.

FINALLY!

After 56 days of no measurable precipitation for Seattle and 57 for Portland, both streaks will end tonight as a relatively strong front moves through the area.

Radar reflectivites at 7:19 pm PDT 8/12/2017 showing a moist Pacific front making landfall.
Radar reflectivites at 7:19 pm PDT 8/12/2017 showing a moist Pacific front making landfall.
Credit: UW Atmospheric Sciences

The front is associated with an upper-level trough/associated ~995 hPa surface low currently centered near Haida Gwaii. The water vapor imagery below looks more reminiscent of a wintertime system than something we’d see in August.

GOES-West water vapor satellite at 07:00 pm PDT, Sat 12 Aug 2017
GOES-West water vapor satellite at 07:00 pm PDT, Sat 12 Aug 2017
Credit: UW Atmospheric Sciences

The front is visible in even greater detail with our brand new GOES-16 satellite, which is still “experimental” and not yet operational at this point. When it becomes operational, it will be moved east to replace the old GOES-East satellite. We will have to wait until the launch of GOES-S in 2018, which is the same satellite as GOES-16, for a replacement of GOES-West. Those darn east-coasters!

GOES-16 Low-level Water Vapor showing a strong front coming into the Pacific Northwest.
GOES-16 Low-level Water Vapor showing a strong front coming into the Pacific Northwest. Image valid 7:17 pm PDT 8/12/2017
Credit: College of DuPage NEXLAB Experimental Satellite

Aided by a strong westerly jet, rainfall amounts are predicted to be highest on the windward slopes of terrain, with isolated locations along the coastal mountains of Vancouver Island expected to pick up to 2 inches of rain. Amounts will range from 0.05 – 0.25 inches in the interior, but all we need is 0.01 inches to end our dry streaks once and for all.

24-hour precipitation ending 05:00 pm PDT, Sun 13 Aug 2017 (36 hr Fcst)
24-hour precipitation ending 05:00 pm PDT, Sun 13 Aug 2017 (36 hr Fcst)
Credit: UW Atmospheric Sciences

Expect slightly cooler-than-average temperatures (which will feel downright frigid after our recent heat wave) to begin next week, with a typical morning clouds/afternoon sunshine routine.  There is a LOT of uncertainty in the extended – so much so that the GFS operational (the “main” GFS that bloggers like myself like use graphics from) and the GFS ensemble control (the ensemble member initialized from the same conditions as the operational GFS, but run at the courser ensemble resolution) are showing completely opposite patterns for next weekend!

850 hPa Temperatures and 6-hour precip at Portland Int'l Airport for the next 16 days.
850 hPa Temperatures and 6-hour precip at Portland Int’l Airport for the next 16 days.

Confidence remains low for your eclipse forecast, but if I had to guess, I’d expect a typical morning clouds/afternoon sunshine routine. Since our eclipse is in the morning, this means your best chance at seeing the corona would be to head east of the Cascades… but it will still be pretty darn cool even if skies are completely cloudy.

One more thing: You can now subscribe via email to these blog posts! Just go to the right hand sidebar if you are on a computer or scroll down below the post if you are on mobile to enter your email address and get these posts delivered to you as soon as they are published.

I hope you are looking forward to the change to rain/cooler temperatures! I know I certainly am. 🙂

Charlie

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