Wednesday, February 17, 2016

The Unusual; Yakima Flooding in Mid-February

The Yakima River has experienced very high flows and brought some flooding the past few days, which is somewhat unusual for mid-February.  Yakima flooding is normally a spring-time phenomenon, caused by melting as temperatures surge.


In this event, the Yakima first flooded closer the the Cascade foothills and then the water surge moved downstream.   Right now, the Yakima gauges near Parker and Kona are near flood stage, breaking all time record flows for this period (see the area map, with red dots at these points, as well as the hydrographs (plots of flow with time)).



As you can imagine, the flux of water into the Yakima system was accompanied by a rapid rise of the Yakima reservoirs.   Here is the proof.
So why the unusual event?   Two big things.  First, we had a temperature surge this week associated with warm, moist southwesterly flow.  Yakima hit 67F on Monday, a record for the date, and 60F on Tuesday.  With a healthy snowpack in the mountains, that resulted in a surge of melt.

In addition, there was substantial rain in the mountains, with the Cascades being hit by 200-400% of normal precipitation during the last week (see below).


For the Yakima and this event....the worst is nearly over.  Temperatures will cool modestly the next few days and heaviest precipitation will be over northern CA, where it is acutely needed.  We have enough.

Northwest Weather WorkshopThe big local weather workshop is less than a month away (March 4-5, Seattle).  If you are interested in attending, the agenda and registration information can be found here.  This gathering is the place to be if you want to learn more about local weather research and operations.

9 comments:

Buddy said...

Hey Cliff. I actually live along the creek that's in the pic. Everything you said is correct but I want to add to it. It was a localized flash flood event affecting small streams draining the higher foothills of the valley. While the larger tributaries did rise significantly, they are capable of holding such volume. The rain near the crest this weekend did contribute to the reservoirs to rise but rain did not play a role in this situation.

So what happened? It has been a very wet winter and believe it or not a snowy one. Yakima is at 7.5 inches of precipitation for the water year and over 30 inches of snow. Well above normal. While the snow in the valley was melted out, the foothills had a couple feet holding several inches of water.

Then the wind hit. A strong mountain wave event Sunday into Monday occurred producing fierce Chinook or others refer as Foehn winds. 2 feet of snow in my backyard melted in 8 hours. It's a like holding a hair dryer to a pile of snow. Very fascinating phenomenon. Go back and look at the GFS wind forecast that day. It was spot on. Amazing tool.

Michael DeMarco said...

Buddy - that's a great local report - thanks for the close-up.

jno62 said...

200-400% of normal.

That silly El Nino.

Thecatguy93 said...

Somebody always has to make a smart comment about El Nino every time it rains. Anomalies happen, not all El Ninos are created equal. Why can't people just be happy that our drought situation is over and California's is being relieved?

Mark said...

Warm weather abounds on planet Earth. Next week looks extra toasty for western Washington too.

Below is an excerpt from WU founder, Jeff Masters:

After recording its warmest year on record in 2015, Earth continued its record-warm streak into 2016, with January 2016 being the planet's warmest January since record keeping began in 1880, said NOAA's National Centers for Environmental Information (NCEI) on Wednesday. The month had the second warmest departure from average (+1.04°C) of any month since 1880, with only December 2015 being warmer. NASA also rated January 2016 as the warmest January on record, but said it edged out December 2015 for being the warmest month in the entire historical record--1.13°C above average. The four warmest months since 1880 (as measured by departure from average in the NASA database) were the past four months. Here are the top five warmest months in the historical record, according to NASA:

1) January 2016
2) December 2015
3) October 2015
4) November 2015
5) January 2007

January 2016 also marked the ninth consecutive month that the monthly temperature record was been broken and the fourteenth consecutive month (since December 2014) that the monthly global temperature ranked among the three warmest for its respective month in the NOAA database. Global ocean temperatures during January 2016 were the warmest on record, and global land temperatures were the second warmest on record. Global satellite-measured temperatures in January 2016 for the lowest 8 km of the atmosphere were the warmest in the 38-year record, according to the University of Alabama Huntsville (UAH). This is the fourth consecutive month the UAH database has registered a record monthly high.

See full blog:
http://www.wunderground.com/blog/JeffMasters/earth-rings-in-2016-with-its-warmest-january-on-record

Ellen Baker said...

We had fresh snow yesterday just above us and the snowline is about 2800' (the trees are loaded). YTD precipitation is 21.77 inches in Glacier as of now, 2/18 noon. Just sharing. Q - is there an official ranking somewhere of "wettest to driest counties"?

Rod said...

Hi Cliff,
Thank goodness Northern California is FINALLY getting some precipitation. Jeez. This "super" el Nino has been a big bust so far.

I am not complaining, Cliff. Or blaming anyone. But wow. What a big fat bust this el Nino has been for California. Southern California has been far drier than even a "normal" year.

Please comment on this, Cliff. I always enjoy an expert's take on this huge failure of expectations.

-Rod

Alex said...

Cliff, I have to disagree with your statement that February floods are unusual for the Yakima, and that most of our flooding occurs later in spring. Our biggest recorded floods- 1933 in Dec and 1996 in Feb...Pulling up a graph of flows since 1981, 8 of 10 highest flows occurred Mid-Nov to February, and all of out biggest events were late fall-winter rain and rain on snow events (the localized rain events in the Cascades create some pretty amazing high-elevation floods and rates of reservoir filling much more rapid than this weeks- compare the Nov and Dec reservoir refill rates in the graph you included to this weeks). Later spring snowmelt does produce consistent high flows (hence higher average flows for a given date) and an occasional moderate flood. Spring floods would have been more common 100 years ago before the reservoirs went in, but even the estimated unregulated peak flow at Parker (eg what would have come down the rivers w/o reservoirs) from 1981 to present would never have exceeded 37kcfs in May. Contrast that with estimated peaks of 50k to almost 80kcfs in each month Nov to Feb. This week's event was a moderate flood on the mainstem, driven by low-elevation snowmelt, and caused almost no issues. We had a significantly larger event just this December (2nd only to 96 on the Naches-huge kudos to the County's efforts to set back dikes etc, which meant little damage occurred compared to past floods of that magnitude). The damages that were reported this week all came from low elevation tribs (Cowiche being the main one) driven by rapid melt of an above average low elevation snowpack; most of the issues came when Cowiche backed up at undersized bridge crossings, and so flowed down ditches into town. It was pretty impressive to watch Cowiche roar!

Doug J said...

Cliff this article from the LA Times may answer why this winter has been so wet in the PNW. Apparently the El Niño is so strong it has created a large area of high pressure over Southern CA, pushing all the storms north. Portland just set a record for the wettest December through February on record. Northern California is well above normal on snowpack. But LA hasn't had the big storms like they usually have in an El Niño year. http://www.latimes.com/local/weather/la-me-el-nino-wimp-20160130-story.html