May 11, 2015

Drought Help

The atmosphere over our region has made a major transition and it appears that the next week or two will be much cloudier and wetter than we have seen in a long time.  The ridge is gone, replaced by deep troughing over the eastern Pacific.

Importantly, the new circulation will bring substantial precipitation to eastern Washington and the eastern Cascade slopes, regions that desperately need the precipitation.

The UW WRF model precipitation for the next 72 hour shows some substantial totals for May, ranging up to  1-3 inches in the Cascades, particularly over the north Oregon terrain.  Eastern Washington is quite wet, as is the Willamette Valley.

Precipitation continues for the next 72 hr, again with LOTS of rain over and east of the Cascades.

A substantial proportion of this precipitation will be from thunderstorms.  In fact, there was a large collection of thunderstorms over eastern Oregon today.

So why the big shift?  Take a look at the upper level (500 hPa) forecast map at 5 PM today (Monday).  An upper trough over Oregon!

 4 PM Tuesday, same general idea.

4 PM Thursday, the trough deepens and extends southward over California.  Folks, this is NOT a dry pattern for the West Coast...and not a warm one either.

Interestingly, the atmosphere seems to be locked in such a configuration for a while.  Not the kind of weather tomato plants like.

Want to really be impressed?--- here is the total precipitation over the western U.S. for the next 16 days (from a relatively low resolution model, the GFS.  Four to 10 inches in some locations.  This has to make Northwest farmers and water managers smile.

Tuesday AM Update: The radar at 5 AM shows bands of moderate precipitation circling around the trough, with particularly heavy rain (yellow colors) over SW Washington and NE Oregon.  This precipitation should move northward today, with moderate precipitation along the eastern slopes of the south-central Cascades.


  1. That much moisture will be mostly welcomed. Some of the burn areas from last summer will experience some washout that did not happen during the almost nonexistent runoff season.

  2. Hmmm this throws a bit of a monkey wrench into the 2070 stress test. These temperatures might be 2 to 3 standard deviations below normal for 2070.

    Interesting that the RRR broke down this May. Last winter it broke down in March leading to record rainfall. What will next year bring?

    Thank you for the informative and wonderful northwest weather blog, Cliff.

  3. Mark....fine for the stress test as long as it doesn't last for the whole summer. There will be cooler and wetter periods in 2070 as is the long-term average values that count. Glad you like the blog...cliff

  4. This is good news for Eastern Washington farmers unless you're waiting to plant corn which requires warm and sunny days.


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