Powerful Winds, Heavy Rain, and Snow: The Perfect Northwest Weekend

This weekend promises a large amount of weather action, with much of the fun yet to come.

Last night a strong warm front moved through, bringing powerful winds in its wake, followed by a cold front.   And a strong, bent-back trough will be here soon, increasing the winds again.  Plus, heavy snow coming in the mountains, and big winds on the eastern side of the Cascades--too much weather for one blog!

Just to give you some perspective, here is the large scale chart for 4 PM yesterday.  Solid lines are sea level pressure, near-surface winds are the pennants, and temperature is color-shaded (yellow and orange are warm, blue and white are cold).   A warm front was approaching our coast at the time (big change in colors) and a fairly deep low was over the Gulf of Alaska (975 hPa).  Winds are very strong in the warmer area--called the warm sector of the storm.

Winds really picked up as the warm front moved through and temperatures jumped--some locations in Puget Sound hit the upper fifties!    He are the winds and temperatures above Seattle-Tacoma Airport as the front moved through (10 AM Friday to 10 AM Saturday).  Time (GMT) increases to the left and the ordinate is height in pressure (850 is about 5000 ft.  On the wind barbs, a solid triangle indicates 50 knots.  A long line is 10 knots.  So a barb and three big lines is 80 knots.  A half line is 5 knots.  Some of the winds aloft got to 50-80 knots and near the surface 20-40 knots were observed.   You can see the big, but temporary, warming aloft as the system moved through.

Here are the maximum winds during the last 24 h:

Lots of 40-45 mph over Puget Sound, but 50-60 mph over the eastern Strait and along the coast. The result has been scattered power outages around the region--50,000-60,000 customers at the peak.

The two fronts are through, but we are not out of the woods yet:  the low center and the associated bent back trough are approaching!  Here are a series of surface charts for 7 AM, 1 PM, and 4 PM today. You can see the low pass to the north of us and an area of intense pressure difference (or gradient) move over western Washington and Oregon.  This will produce a profound acceleration of the winds from the south, with winds gusting to 30-50 mph again in the lowlands.  More scattered power outages.   It will be breezy during the Seahawks game and footballs will be pushed to the north!

What about precipitation?  The freezing level is now rapidly dropping and we had a break in the action as the front passed.  But now the convective showers are now approaching (visible in the current radar and infrared satellite pictures)

 Snow is about to begin in earnest in the Cascades.  The current 24-h snow amount forecast for the period ending 4 AM Sunday (see below) indicates 1-2 feet, with low-level Snoqualmie Pass on the lighter side.

Now this blog is getting long...and there is much I haven't touched on.  Another system comes in on Sunday.  More strong winds. And a very intense pressure trough will develop on the eastern side of the Cascades, that may produce powerful downslope winds there (see wind and sea level pressure chart for 1 AM Monday morning).  This forecast suggests sustained wind of 35-40 kt on the eastern slopes, with far higher gusts.

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Finally,  if any of you wish to help my colleague's (Becky Alexander) research project on understanding the ozone impacts of gas fracking, the deadline is 5 days away.  In this crowdfunding approach, if the entire sum is not reached the project is not funded.  Right now she is about 70% of the way to the goal.  Here is the information:

Fracking and Ozone

UW Professor Becky Alexander has established a page on the Microoryza crowdfunding web site that outlines her project  to understand why natural gas fracking often leads to high ozone values over snow (go here to see it). If you want to learn more about this important project and how you can help it happen, check out the web site.