Saturday, April 11, 2015

The Atmospheric Spigot Turns on For the Pacific Northwest

Water worries for the Northwest continue to fade as a series of very wet systems hit the Northwest this weekend.

Friday afternoon brought an intense cold front, with bands of heavy showers over western Washington (see regional radar image at 5:51 PM Friday).  Yellow and orange indicate very heavy showers.


Here is the 24-h precipitation totals ending 8 AM today (Saturday).  Substantial amounts on the western sides of north Cascades and Olympics (around 1.5 inches), but the rain shadowing was impressive with only about .01 inch over the San Juan Islands--those folks live in Paradise.  Eastern Washington was dry.



After the front moves through, the upper atmosphere turns westerly, with a huge powerful jet bringing west-east flow over the entire eastern Pacific (see graphic for 11 PM Friday night at 500 hPa, about 18,000 ft, yellow colors are the strongest winds and winds are powerful to the height lines).  A powerful hose is aimed right at us.

Westerly flow produces strong uplift and precipitation on the western sides of our mountains, but lee rain shadows to the east of the mountain crests. And so the forecast show.  Here is the 72-h total precipitation ending 5 AM Monday.  1-3 inches in the mountains and the western slopes.  But bone dry in Yakima!

The air will be cool enough for substantial SNOW in the mountains--here is the 72-h snowfall total forecast by the UW WRF model.  Up to 2 feet in the WA Cascades and LOADS of snow around Whistler and the BC Cascades.  


All this is happening after Seattle Public Utilities have brought the city reservoirs to very high levels.  So Seattle's water situation looks extremely good.  

The long-range forecast for the subsequent 72h period keep Washington moderately wet but hits southern BC very hard, with 2-5 inches of precipitation (see first map below) and HUGE amounts of snow (see snowfall for that period in second map).  Even the north Cascades gets a piece of this.



Unfortunately the weather pattern is not favorable for arid California, but increasingly it looks like the Pacific Northwest will have adequate water supplies, even with a below normal snowpack.

4 comments:

Lori said...

I'm currently in "bone-dry", arid California. The contrast is really stunning. I can hardly wait to get back to green, rainy home!

Cristina said...

Please encourage Seattle Public Utilities to keep the Roosevelt reservoir available. Not only based on the high density low-income buildings planned North of the ship canal, but also because outlying areas around the city are still heavily dependent on snow-pack as climate change gets ahead of their infrastructures to adapt.

jno62 said...

Hey Cliff,

I've read 3 national head lines about how some "blob" of warm water has been affecting the weather in the US this year.

Where have I heard that before.....?

Dalton said...

"but increasingly it looks like the Pacific Northwest will have adequate water supplies."

Tell that to the farmers in the Yakima basin or the orchardists in the Wenatchee valley, or the fire fighters in Okanogan-Wenatchee National Forest. There's more to this state than Seattle, Cliff.