February 05, 2015

Atmospheric River Update

 Here is the 24-h precipitation ending at 9 PM today (Thursday).  Almost 5 inches of rain on the upper western slopes of the Olympics and up to 3 inches over the western side of the North Cascades.  But Mama Mia!   What a rainshadow!  Less than one-tenth of an inch over northern Whidbey Island and the southern San Juan islands.

The freezing level has risen to about 8,000 feet and it is raining in the passes.   Sorry skiers!

It has started to rain in northern California, but the big action there is yet to come.   Here is the 24-h rainfall ending 9 PM today.  Some of the coastal mountains have already received more than 4 inches, with 1 inch+ spreading inland. The models are predicting over TEN INCHES in the northern CA terrain during the next 72 hours.

I don't know about you, but I am getting very bored with the warmth and rain.   We need some more variety.  How about a big windstorm?   No problem....the models have been suggesting one for a while and here is a forecast map for 7 PM Sunday.   Impressive system off the Oregon coast....will have to watch this carefully.

Wednesday, February 4, 2015

Triple Atmospheric River Event to Hit the West Coast

Probably the most significant West Coast heavy rain event of the winter will occur during the next few days, with Northern California being the hardest hit.  Three "atmospheric rivers" will strike the coast between now and Sunday, with the middle one possibly being the strongest in years.

A microwave satellite image taken around noon today shows the first (and weakest) atmospheric river of the three.  This graphic shows the total amount of water vapor in the column, or more exactly what depth of precipitation it could form.  Atmospheric rivers are narrow but long currents of moisture and warmth, with roots in the tropics and subtropics.

The forecast for 1 AM tonight shows this moisture plume reaching the Northwest coast.

The second, and far stronger atmospheric river, is apparent on Friday at 10 AM. The blue values are very large.  This system will bring very heavy rain to northern California.  Why does the moisture plume end quickly at the coast?   Because much of the moisture is forced to condense out by regional mountains.

And then a third atmospheric river, and a very broad one at that, is seen early Sunday.

The model forecasts are quite stable for the heavy rain;  here is the WRF forecast the next 72 hours.   Amazing totals over California, reaching over 10 inches. The Washington mountains get nearly as much!

But the rain does not stop there.  Below is the next 72 hour. A bit less, still heavy 
over Northern California.  This is enough water to bring flooding, and the CA/Nevada river forecast center  is going for significant flooding (see graph, red dots indicate flooding conditions)

The Pacific Northwest Weather Workshop

Interested in attending the big local weather workshop of the region?  The Pacific Northwest Weather Workshop will be held in Seattle at the NOAA facility on February 27-28th.   Everyone is invited and the majority of talks are accessible to laypeople.  To attend you have to register or they won't let you in the gate.  There will be a major session on the Oso landslide.  There is a registration fee that covers refreshments and food, and special student pricing.  If interested, check out this website.

Climate Change and the Pacific Northwest

I will be giving a provocative talk on this subject on March 11th at 7:30 PM Kane Hall on the UW campus in Seattle.  Sponsored by local public radio station KPLU, tickets for this event can be secured at this web site.


  1. I don't mind soggy, but could do without a wind storm!! Send it further off coast, Cliff.

  2. Is there public access to the maps with the 24 hour precipitation observations by station (not just the static images in your post)? Thank you.

  3. Dan,


  4. USA is always very cold in winter, and has a big wind.

  5. Wow! Lake Shasta, Calif inflow at 50,000 cubic feet per second. http://cdec.water.ca.gov/cgi-progs/queryF?s=SHA&d=06-Feb-2015+23:04&span=12hours


Please make sure your comments are civil. Name calling and personal attacks are not appropriate.

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