A very potent Westerly Atmospheric River (WAR) event is coming, with heavy rain and flooding. Another drought-buster event that will fill our reservoirs. And there is more: plenty of wind and high surf on our ocean beaches.
A recent infrared satellite image shows a plume of high clouds associated with the approaching moisture and strong winds (see below).
And the latest UW WRF forecast for Thursday night at 7 PM shows the high moisture value (red colors) aimed right for us. It looks like a fist. This is an example of an atmospheric river, a plume of large moisture values, but it is not a pineapple express--those events bring moisture from the southwest near Hawaii. In this case moisture is streaming northward over the western Pacific and then heading nearly due east towards us, Westerly Atmospheric River.
The NOAA/NWS River Forecast Center is predicting flooding on many western WA rivers, several reaching moderate flood levels (see below). So be careful in the normal flood-prone spots.
Now I know my snow loving friends are getting nervous about this atmospheric river event.
Atmospheric rivers usually bring warm rain through elevation, which is not exactly good for snow. That is true...but this case is not a pineapple express so temps will be a bit cooler and the period of warmth will be relatively short (about 36h). The snowpack will be knocked back a bit at lower elevations, but some of the rain will freeze in the snow. And higher elevations will have a net snow gain. Let me show you.
The UW WRF model suggests that next 72 still bring some snow to the higher elevations (see below)
But the exciting thing is that after the atmospheric river passes through on Monday, we moved into colder air with lots of shower activity....and large amounts of snow (see below for snowfall for 72 hr ending 4 PM Wednesday). Feet of snow over the entire Cascade Range. Ski season begins.