An Intense Front, Strong Winds, Heavy Precipitation, Flooding and Big Waves: The Northwest Will Be Hit By Everything

 Today will offer something for every meteorological taste, except for sunny and warm.

The front page of the National Weather Service's web page is lit up with almost every imaginable meteorological warning and advisory (see below).  High wind warnings, storm warnings, winter weather advisory, high surf advisory,  flood warnings, and more.

And the latest water vapor satellite image shows a very impressive plume of moisture poised to move into our region.  I mean THOUSANDS of miles long.

During the 36-h ending 4 AM Sunday, models are predicting up to 5 inches of liquid water equivalent in the mountains.

And by 4 PM Monday 5-10 inches of water will be widespread.

Considering that we are starting with rivers running quite high (see figure below), some flooding is inevitable.   The blue dots indicate river measuring sites where the flow is ALREADY much above normal.

For example, the Tolt River, draining off the central WA Cascades, is predicted to surge to moderate flood level.

But for me, the big excitement is a very intense cold front that will approach our shores later this afternoon.   This winter we have had several of them, including the one that brought the snow a few weeks ago.  The exciting thing for me is that our models have been capable of realistically simulating and forecasting these amazingly intense features.

To illustrate, here is the super high-resolution forecast by the UW model for 7 PM tonight, showing surface wind gusts (color shading) and surface winds (the wind barbs) along the WA coast.  Look closely and you will see an extraordinary sharp and dramatic wind shift from southwesterly (from the SW) to northwesterly winds.   THAT is the front.

This sharp wind shift is associated with tremendous convergence of air at the surface, forcing intense upward motion and heavy rain, something that the model is simulating (see the simulated radar image below for the same time).  

You see the undulating orange line on the coast?  THAT is the intense rainfall associated with a strong narrow cold frontal rainband, stretches northeastward to north of Everett.

Trust me.  You do NOT want to be outside when that hits.

And let's not forget about wind.  A strong pressure gradient (wind difference over distance) will precede and accompany the front, and many of you will experience winds gusting to 40-50 mph.  The latest NOAA HRRR model forecast of surface gusts at 11 AM this morning shows gusts as high as 50-60 mph

along the coast and over NW Washington, with lesser, but still strong, winds over Puget Sound.

Now let me show you a high-tech wind product we make available to Seattle City Light from the Seattle WindWatch website. (They use the skillful wind forecasts to deal with power outages).  This guidance shows the high-resolution forecasts, the ensemble of many (slightly lower resolution) prediction, and new guidance making use of machine learning for max wind gust over Seattle.  Time is on the x-axis and predicted gust is the y-axis.

The winds will increase during the day and hit a peak during the late afternoon and early evening, plummeting after the front moves through.  Quite a bit of uncertainty, with the highest winds around 50 mph.  Machine learning is knocking the winds down to 30-40 mph, while the high-resolution models going 40-50 mph.

The application of machine learning is a new technology for weather model calibration and we have a lot to "learn" about applying this approach.   With saturated soils, I expect there will be scattered power outages.   In the future, perhaps, we will use machine learning to directly predict the power outages based on preceding and forecast conditions.

Enjoy the active weather.