A SuperFront Will Cross the Northwest This Weekend

Most weather fronts that cross the region are unremarkable due to their passage over the relatively warm, uniform waters of the northeast Pacific.  

This weekend will be different:  a  SuperFront will make landfall late tomorrow (Saturday).  

Some of you will lose power.

Let me show you simulated radar images for three times:  10 AM, 4 PM, and 9 PM on Saturday from the UW high-resolution forecast system (from the 4-km grid-spacing domain).  Red indicates very strong winds, followed by yellow.  The arrows point to the frontal locations.

Wow. Very intense, sharp front.  Very heavy rainfall.

The high-resolution 1.3 km simulation run by my group at the UW produced an even more intense front (forecast around 8 PM shown).  Very impressive.

What about the predicted winds?

The City of Seattle supports the most high-tech wind prediction system in the country (called SeattleWindWatch, run at the UW), which includes an ensemble of many wind predictions for estimation of the uncertainties.  

The forecast below is for the winds over Seattle.  Several of the simulations predicted winds reaching 40 mph. Over the water, winds could be stronger,

 Winds will rev up after dinnertime and peak overnight.

Such strong winds, this early in the wind season when some leaves are still on the trees, mean power outages.  

As noted above, wind will be strongest over the water (see forecast below for 4 AM).   I suspect most of the power outages will be in such areas.

For the whole region, the strongest winds will be on the coast (see map of strongest wind gusts below).  Importantly, there will be areas of intense gusts on the lee/downstream side of some of our highest terrain, including the eastern slopes of the Cascades.

In addition to wind, the front should bring substantial ( and welcome) precipitation to the region, with the total through 4 AM Sunday shown below

So, if you live west of the Cascades,  get your meteorological popcorn out and be prepared for a dramatic meteorological show later tomorrow and early Sunday.

Wind, Waves, and Wet

This weekend, we will "enjoy" the meteorological trifecta of winds, coastal waves, and substantial precipitation.

First, the winds.

The forecast sea level pressure for Sunday at 10 AM predicts a strong 994 hPa low center to west of the Washington coast.

The associated winds (below) are impressive, with sustained winds of 50-60 knots to the south and west of the low center.    This is known as the "poisonous tail" in the weather business.

Such strong winds over a large area (large fetch) will produce large waves that will reach our coast later this weekend (see below).   These waves will climb to 45 feet offshore and over 20 feet on our coast.

There will be good wave watching on the Washington coast on Sunday.

As the low moves northward up the coast on Saturday and Sunday morning, wind gusts will increase along the Washington coast and   over the western Washington interior  

The forecast gusts at 4 AM Sunday are shown below.  Strong gusts (50 kt and more) on the coast; 30- 45-knot gusts in the interior, particularly near the water.

The UW runs perhaps the most sophisticated wind prediction system in the country for Seattle City Light (called WindWatch), and it is predicting 40 mph gusts in Seattle on Saturday night and early Sunday. (see below)

As the first major blow of the season, with lots of vegetative growth over the summer, there will be power outages.

 

My "pro-tip":  charge up your electronics and lights on Saturday.  You won't regret it.

Finally, there is the wet part of the upcoming weather.

Below is the predicted precipitation accumulation through Monday at 4 AM.  Very wet in the Olympics and the northern Cascades.  Plenty elsewhere.  Reservoirs will begin to fill.

This is just the beginning of the wet/stormy season in the Northwest, with a lot more on the way.   Typical November conditions, and there is no going back.