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.