Monday, December 8, 2014

Where's the Snow?

We're now into the second full week of December, and most of us in the Inland Northwest haven't seen much snow yet.  The notable exception is the folks in the Methow Valley, which received up to 18" from a storm just before Thanksgiving.  Outside of that, most locations have seen a dusting here, half an inch there, but nothing that survived for very long.  

So the first question often is "Has this ever happened before?"  Our climate records for this area generally go back into the early 1900's with some sites having data into the late 1800's.  And some sites have good, continuous data, while others are a bit spotty.  So lets take a look at a few sites that have good data and are representative of the area.

First we have to define how to look at the early season snow.  The first measure is fairly obvious: "How much snow do we normally have by this date?"

Avg Snow through   7 Dec
Total Snow 
7 Dec 2014
Lowest Snow through 7 Dec
Spokane Airport
0.3” in 1954
Wenatchee WP
0” in 2012
0” in 1904
Priest River
0” in 2002
Trace in 1943
Trace in 1969
0” in 1920

As you can see, in most locations, we're behind our Average snow fall through December 7th.  But we're still doing better than other bleak years.  So no records there.

Another way to look at it is the average date of the first inch of snowfall. 

Avg Date First 1” Snow
2014 First 1” Snow
Latest First 1” Snow
Spokane Airport
Nov 19th
Not Yet
Dec 23rd 1976
Wenatchee WP
Dec 6th
Nov 22nd
Feb 1st 1963
Nov 22nd
Nov 29th
Jan 4th 1990
Priest River
Nov 14th
Nov 25th
Dec 15th 1926
Nov 13th
Nov 22nd
Dec 23rd 1976
Nov 12th
Nov 22nd
Dec 11th 1936
Nov 20th
Dec 4th
Dec 25th 1954

Again, most locations got a late start, but nothing that would break any records.  The exception is the Spokane metro area, which has yet to even have it's first inch of snow.

So what's been the cause of this lack of snow?  Here's the average temperature for the Nov 1st - Dec 5th period.

As you can see, for the past 30 days it's been actually colder than normal for the Inland Northwest.  Of course, this is an average of 2 cold snaps with some rather mild weather in between.  Here's the daily temperature data for Spokane:

The blue bars are the daily temperatures, while the red and blue shading shows the daily records.  Spokane hasn't had any record highs or lows during this period, but they've come close.  The mild temperatures are certainly not conducive to snow.  But what's frustrating is that the cold snaps didn't equate to much if any snow.  Typically, cold air that moves in from Canada is very dry and doesn't provide much snow, which was the case with both of these systems.  But then eventually a Pacific storm will bring moisture into the area and it will fall as snow until the cold air can be pushed out of here.  But in both of these events, that didn't happen.  Instead, the Pacific storm went south of our area, leaving the Inland Northwest largely dry.

The percent of average precipitation shows that after a promising start to the wet season in late October, we've been fairly dry over the past 30 days.

So what has this meant for the mountain snow pack?  It's not good.  Here's the Snow Water Equivalent (SWE) analysis (i.e. how much water is in the snow that's on the ground).  The color shading represents the comparison of this year to how much is typically in the snow pack by December 8th:

It shows that most of our area is lagging behind normal at this point.  While this is bad news for ski enthusiasts, it's way too early to worry about it from a water supply standpoint.

Is there any hope of a change in the weather?  Not really.  Here's the 8-14 day outlook for temperatures and precipitation from the Climate Prediction Center (CPC).

The folks at CPC see warmth for next week across just about the entire US, while precipitation is expected to be near to below normal for mid-December.  This is an average outlook for a 7 day period.  So there can still be a weak snow event buried in there, but it's not likely.  And since this outlook ends on December 22nd, the issue of a White Christmas is starting to come into play.

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