Saturday, November 14, 2015

Large Snowfall will Hit the Cascades and Olympics

8 AM Sunday Update

The cold air was a bit delayed, but it is here now and the models were correct that the snow level would descend quite low.  Here a picture from Peter Benda, looking out over Cougar Mt.

And Stevens Pass is quite white right now:

One of the best snow situations in a long time will hit the our regional mountains during the next few days, with some snow even reaching the lower terrain slopes.

Enough snow that will assure pre-Thanksgiving openings of a number of our local ski areas.

Let me start with the exciting stuff first.  Here is the predicted 72-h snowfall map for our region from the UW WRF system.

 Over two feet of snow over the north Cascades and the Olympics, with large amounts also over the mountains of British Columbia the and Oregon Cascades.

What is so stunning about this plot is that the snow extends to lower elevations...not sea level, but certainly down to around 1000-1500 ft.

This snow will fall on a decent base, as shown by the NOAA snow analysis for Saturday AM, which indicates healthy amounts (up to 20-30 inches) over the north Cascades and southern BC.

You may ask, why are we getting so much snow, during an El Nino year?  

Actually, El Nino years can bring decent snowpacks overall (down by about 20%) and El Nino effects often don't become profound until after the new year.   The current large scale atmospheric circulation is very much NOT an El Nino one.   For example, the upper level (500 hPa) forecast for tomorrow afternoon shows a big ridge north of Hawaii, with a deep trough over the western U.S.

El Nino years tend to produce a TROUGH in the same location... practically the opposite (this is shown in the figure below that provides the typical anomaly(difference from normal) of 500 hPa heights).

Major snow action will occur tomorrow as a low/trough moves past us, with cool northwesterly flow invading our region.  The map below shows the heights, winds and temperature around 5000 ft (850 hPa).  Northwest winds and cool temps (greenish colors) over and upwind of the Cascades.  Major snow producer.

Let me show you something new...our uber-resolution (1.3 km) WRF forecasts.

Here is the 24h total ending 4 AM Sunday.  Lots of snow in the north Cascades and Olympics. (1-1.5 ft).  Even the tops of some of the Issaquah Alps get it.

But the next 24h  (ending 4 AM Monday) are really something different (see below).  Snow from 1000 ft on up and even some snow getting near sea level south of Tacoma.  Amounts are modest (4- 8 inches).   Not much in the Olympics.


Greg Magone said...
This comment has been removed by the author.
adam said...

I agree

ryamkajr said...

Snow level - the point at which rain/snow transition.

At present (this time of year) the level is dropping, and at times drops far enough down to pass levels (3000-4500ish range). This drop is not yet a sustained drop, that comes as we move into winter. So yes, there will be snow at the passes, but this is measured in inches at this time.

allen hall said...

It can't pile up when each warm front starts off the cycle. I think the Blob is still running the show.

Chaz Bradworth said...

Mt. Baker doing good and should open by Thanksgiving. Snoqualmie Pass not so much. Feels like remnants of the blob are still here.

Unknown said...

The temp anomalies that are expected with a strong El NiƱo year don't became very apparent until January based on the following composite historical data. In fact historical average anatomies as shown in the following piece are historicallynearly neutral for November. So based on this I would expect things to go downhill on the snow front so to speak after the first of the year.

Craig Armstrong said...

Still early but I'm getting snow forecasted next sunday and monday...

Buddy said...

I'm agreeing with the over zealous of snow. Yes we've missed it for 2 years now but everyone needs to settle down. There's been 3 or 4 posts of snow and if you look really hard you might see a blob at 6000'. Stating Whistler or Baker might be open before thanksgiving is a broad generalization, areas that have been on the cusp, is a misrepresentation to all other resorts in the Pacific Northwest. It has yet to rain a drop in some parts of the state or snow a flake at some resorts. I respect your blog and book because it covers more than what one neighbor to the north may be doing.

Thecatguy93 said...

Yep, don't believe the hype. Winter storm warning for the north Cascades has already been dropped. Most snow that falls between now and Monday will be wiped out during the following three plus days of 7000 foot snow levels and heavy rain. Not only will Snoqualmie not be open for Thanksgiving, my guess is there will be no snow on the ground at all.

Cedarspring said...

It is snowing hard right now at 8:25am in Auburn at an elevation of 400ft. WOW.

Jenny said...

Any word on what we can expect in eastern Washington?

hidden wave said...

Mt. Baker already has close to 40 inches with much more forcasted for today and tomorrow. The warm up will occur between 10am and 4pm according to NOAA and then more snow Tuesday night at Baker. These warm ups are actually good for base building. You want to settle out and solidify the early season base for a good solid and longer lasting run. Layers my friend. We'll be shredding up north this week naysayers! I wouldn't put my money on snoquamie pass though.

Weatherfreak said...

Now this was a nice surprise... 42 and rain last night at 11am only to wake to snow falling and 33 with wet dusting on the tree's and grass this morning! All at 550' in SE Auburn. Snowed for about an hour and half just enough to take the first snow walk of the winter. Still 36 at 10am. Didn't see this coming since the air mass didn't seem quite cold enough. Looks like another fun 3 days of weather ahead!

Anonymous said...

About an inch here in Eatonville. Yay! Hoping this isn't all we'll get this winter! Hoping you will do a write up on the wind event the nws is talking about. They're making it sound like it's going to be a really big deal. But they haven't suggested how far south the high winds may reach....will Eatonville be lucky enough to get high level winds? Or just advisory level?

Westside guy said...

This is clearly an anomalous snow event forecast. I can demonstrate a strong correlation between November snowfalls and our planned trips over the mountains to visit my wife's family - but no such trip is on the books for this upcoming week.

Unknown said...

@windlover: See here: Looks like all of western WA.

Unknown said...

are we in for a windstorm on tuesday?

Unknown said...

What about the wind storm on Tuesday? Gusts to 75 mph?!! NWS forecast discussion today at 4:20:


Anonymous said...

It may be too early to say for sure, but it looks like a large ridge is setting up for late in the week. So marginal snow conditions in the passes may be followed by dry clear weather for a week unless a short wave or two makes it over the ridge. Then we could see some lowland snow. But now I'm really getting ahead of things.

Anonymous said...

Another will Tuesdays winds compare to the Hannukah Eve storm in 2006?

Angela said...

Weather Underground has this to say about Tuesday's forecasted winds:

... High wind watch remains in effect for The Lowlands from
Tuesday morning through Tuesday evening...

A high wind watch remains in effect from Tuesday morning through
Tuesday evening.

* Wind... south or southwest 25 to 40 mph with gusts near 60 mph
are possible on Tuesday.

* Some affected locations... Everett... Shelton... Bremerton... and

* Timing... the strongest winds are anticipated to occur during the
day Tuesday... with the exception of the Strait of Juan de Fuca.
Strong winds over this area will probably hold off until late in
the day or Tuesday evening.

* Impacts... high winds can down trees... damage property... and
cause power outages.

Precautionary/preparedness actions...

A high wind watch means there is the potential for a damaging
wind event. A high wind watch means there is the potential for a
damaging wind event. Sustained winds of at least 40 mph and/or
gusts of 58 mph or stronger may occur.

Gary said...

Olympia: After almost 72 hours of continuous rain--starting ~9am Thurs and not stopping until 8am today Sunday--all day today we had non-stop SUNNY weather with blue skies, fall colors and mild breezes! I was outdoors snapping photo after photo focused mostly on the brilliant, cloud-free sky.

Tonight, after reading the forecasts for the next two days--potentially destructive gales, downpours, flooding, and snow in the mountains--I took one more look outside, before bed: 36F and clear; right here in Anomalous Olympia.