More Threatening Weather at the Oroville Dam

11 AM Monday Precipitation Totals

Some of the terrain about the dam has received over 4 inches already.

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The latest forecasts are worrying regarding the heavily damaged Oroville Dam in California.  And I am surprised there is to so little talk by CA state officials and the media about the danger.

During the past few days, with little rain and active drainage of water, the dam level has been reduced substantially (see image)

But central California and the Sierra Nevada mountains are about to be hit again...quite hard, with a strong atmospheric river (see moisture plot for 1 AM Monday).  The red and white colors shows high column integrated water vapor values.  Aimed right at the dam.

The forecasts show substantial precipitation with this atmospheric river.  Here is the accumulated precipitation for the 24h period ending 4 PM Monday from the excellent NCAR high-resolution ensemble system (the ensemble mean). 4-8 inches over the Sierra.

But that is the ensemble mean or average.  But there is a chance it could be more, so here is the ensemble maximum, the ensemble member with the highest amount of precipitation.  Much more (30-50% more in some locations)..and a serious problem for Oroville Dam.

The 48h precipitation total ending 4 AM Tuesday from the GFS model projects 5-10 inches in the mountains.

And the European Center model has the same idea, with 5-7 inches

Looking at the NCEP SREF ensemble system at Blue Canyon, about 15 miles away from the dam,  shows an ensemble mean of 7 inches, with a range from 5.5 to 13 inches.  Great confidence for a major rain event.

Hydrological forecasts by the National Weather Service, project a rapid rise of the Feather River, the main feed into the reservoir behind the dam, with the flow quadrupling from around 7.5 thousand cubic feet per second to around 32 thousand.

This is a dangerous situation and, as always, there is uncertainty with our forecasts.  Why is there so little discussion of the rapidly increasing precipitation?
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And if you want to read an interesting blog about an unusually strong cold front that hit Hawaii, check this out:

http://hawaiianweather.blogspot.com/2017/02/cold-front-passing-hawaii.html

Will Seattle Beat the All-Time February Precipitation Record? Almost Certainly Yes

Sunday morning update:  SEA how has 8.01 inches,  1.10 inches below the record Feb total.
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People love records.   And precipitation records are falling over the West Coast.

Here is Seattle, the record February precipitation is 9.11 inches, which fell in 1961.

As of midnight, Seattle Tacoma Airport had 7.85 inches so far this month.
Since then, Sea Tac got another .07 inches, so we are now at 7.92 inches or 1.19 inches behind the record.  A plot of actual (red) and average (blue) cumulative precipitation at Seattle shows the story...we are about 6 inches ahead of normal now.

Looking at the forecasts, we have a very good chance exceed this.   For example, here is the precipitation forecasts for Seattle from the European Center ensemble and high-resolution models.  1.3 inches for the ensemble and 1.7 inches for the high resolution forecast.   If true, the record is toast.

Or the UW WRF forecast for the 72 hr starting at 4 AM this morning. The purple color is more than 1.28 inches.... very close.  And there is more rain after that.

So the chances are very good that a new February rainfall record will be set at Seattle Tacoma Airport and a number of other western WA locations.

All this precipitation has caused our soils to become highly saturated, resulting in mudslides and slope failures, such as the one that closed down I-90 near Issaquah and another that closed I-5 near Woodlawn (see below).

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Northwest Weather Workshop:  

The Northwest Weather Workshop, the big annual weather gathering in the Northwest, will take place on March 3-4, 2017 in Seattle (NOAA Sand Point Facility).   Everyone is welcome.  For more information and to register, go to https://www.atmos.washington.edu/pnww/