Saturday, July 2, 2016

Traditional July 4 Weekend Weather

For the last several years, the Pacific Northwest has been fortunate during the July 4th weekend, with sunny warm weather.   Some folks called it the "new normal."

Well, the "old normal" is back, with the traditional clouds and light showers.

The key issue is that the upper level pattern has been stuck for the past several weeks in a configuration with a trough over the Northwest, in contrast to the persistent ridge of last year.   To illustrate, here is the forecast 500 hPa (roughly 18,000 ft) heights for 8 PM today (Saturday).  A distinct trough is approaching British Columbia.   An unusually strong jet stream is approaching our region (the gradient in the lines is proportional to wind speed)

We have had one mobile trough after another move through, each deepening the marine layer and producing some light rain.  The infrared satellite Saturday morning shows this clearly, with a weak disturbance over Washington this morning. The next one is offshore.

The trough Saturday night and Sunday AM will be strong enough to bring showers to the coast and northwest WA, with a few sprinkles getting as far south as Tacoma.

What about Monday and fireworks time?   Here is the upper level map for 5 PM Monday.  Still general troughines over our region, but the main axis has pushed past us.   Models suggest partly clouds skies, but dry on Monday evening, so we will probably have decent fireworks watching conditions.   But don't expect a heat wave:  high temperatures will probably only rise to around 70F on Monday.


Mannes said...

I'm surprised to see that showery forecasts persist until July 10th. I don't recall such a rainy start to summer since 2010. Do you see this as normal or somewhat abnormal?

Evert said...

WOW yep - Happy 4th of November. I hope we don't get totally skunked on summer before it's all over & we're back to full time nine-ten months of cold dark & wet until 2017.
This reeeeeeally sucks.

Chantelle said...

Last year it was 90 degrees and dry as a bone, with fire danger high. I'll take this.

Molly said...

To me it does not suck! I love it! I cannot tell you how miserable the last two summers here made me, with the never-cool-enough nights and scorching dry days and dying gardens. Mild summers with minimal heat are one of the main reasons I chose to live up here rather than in California or other hot climates. This is our proper NW weather and I'm glad to see it back. Happy rainy 4th, just as it should be. :) Everyone in the moss/fern personality camp can come right on over here and hang with me.

AnneScott said...

I think you mean 2011 which was a cool rainy summer.

Tom Stone said...

Could this be an early sign of a strong La Nina? A hopeful NW skier would like to know.

Snoqualmie Joe said...

What Molly said!!!!!!!