Winter Arrives Tuesday

We've had unprecedented warmth this Autumn season.  But all that is about to end.  First, let's take a look at how warm it's been.  

October was a record warm month is some locations.  Here's a quick table showing the warmth:

•  Wenatchee
• Oct 2014: 56.6F - 2nd warmest October
• Record: 57.3F in 1988
• Spokane
• Oct 2014: 53.3F - 5th warmest October
• Record: 54.5F in 1952
• Lewiston
• Oct 2014: 57.9F - 3rd warmest October
• Record: 58.7F in 1988

The warmth actually extends back into mid-September.  Here's a graph of the temperatures at Spokane Airport for the last 2 months:

The blue bars are the observed high and low temperature this year.  The brown shading is what we typically see for temperatures on these days.  And the blue and red lines are the coldest/warmest temperatures ever observed.  So you can see that we didn't set any daily records at Spokane.  But notice how the observed temperatures were consistently above normal, with just a few cool spells.  Add to that, Spokane didn't reach the freezing mark until Nov 2nd, which ties with 2005 as the latest ever for the Airport first freeze.  

But as we said, all of that is about to change, and in a big way.  Here's the weather pattern that is going to do it.  Below is a depiction of the temperatures at about 5000' above sea level for this afternoon (Friday 7 November):

850mb Temperatures Friday afternoon 7 Nov 2014

This image shows that the coldest air is over north-central Canada with mild air over all of the western US.  Below is a forecast for Monday morning:

850mb Temperatures for Monday morning 10 Nov 2014

Now the cold Canadian air has penetrated into the northern tier of the US.  You can see that the Inland Northwest is right on the edge of the cold air.  By Wednesday morning, even colder air has made its way into the lower 48:

850mb Temperatures for Wednesday morning 13 Nov 2014

By this time, cold air has completely moved into all of Washington and Oregon east of the Cascades.  Even Portland will probably see some cold air seep through the I-84 Gorge.  Also note how far south the cold air will move in the central US, all the way down to the Texas Panhandle.  The coldest air will be over Montana into the Dakota, but the Idaho Panhandle will still be plenty cold.

What's causing this pattern shift?  In part, it's Super-Typhoon Nuri in the western Pacific.  Nuri developed east of the Philippines on Halloween, rapidly strengthened, and "recurved" into the westerlies.  The CIMMS blog has some great satellite images of it.   

As Nuri moved northward, it converted to an extra-tropical cyclone, and has currently become a massive storm in the Bering Sea.  So why does this affect our weather?  First, he's a graphic showing the jet stream today.

Jet Stream analysis Friday 7 Nov 2014

The yellow line represents the jet stream.  As you can see, the jet stream is coming at us from a very southern latitude, just north of Hawaii.  But as Nuri's remnants develop and move into the Bering Sea, the weather pattern will shift.  

Jet Stream forecast Monday 10 Nov 2014

By Monday, the jet stream will be directed from the central Pacific into Alaska, where it will pick up cold Canadian air, and bring it southward into the lower 48 states.

So how cold will it get?  Here's the forecast high temperatures for Tuesday.

That's right.  High temperatures on Veteran's Day will be below freezing for much of the Inland Northwest.  And here's the forecast low temperatures for Wednesday morning:

Yes, you're reading that right.  Low temperatures in the teens in many places.  This is way colder than anything we've seen this Autumn.  If you've been putting off those Fall Chores (e.g. blowing out sprinklers, putting away hoses, etc), this weekend will be your last chance to do that.

And with these temperatures, people will naturally be wondering if there's any snow that will come with it.  About the only chance for snow will be in the northern Panhandle and northeast Washington on Sunday Night and Monday Morning.  Here's the current forecast: