Saturday, December 17, 2011

How is the snowpack doing?

The short answer:  not too good.  Something that is surprising in a La Nina year, when snowpacks should be above normal.

Take a look at the latest snow water equivalent map for the west (this is the amount of water in the snowpack compared to normal). The Cascades are near normal due to the considerable fall received last month--but that snow is aging fast.  Oregon and Idaho:  well below normal.  California's Sierra's are roughly 25% of normal.  You want snow?--head to Arizona and New Mexico, where some locations are nearly 300% of normal.  This is due to the frequent troughs and cut-off lows that have moved into that region due to the persistent high pressure over the eastern Pacific.


 Talking of persistent---current models suggest the east Pacific ridging will remain in place at least for the next week--although with weaker amplitude.  This will allow occasional weak fronts to move through--such as the system expected tonight and Sunday morning.  Here is the latest 6-10 forecast from the National Weather Service's Climate Prediction Center---dry over the west.  With such east Pacific ridging, a lot of our moisture is going into Alaska, where they are getting hammered.


Here is the upper level chart for Christmas Eve.  The ridge is so large and high amplitude, Santa will be blown way up into Alaska.  Favorable conditions for dropping down a chimney---nice and dry.


 Talking of snow conditions, the frequent periods of clearing over the mountains have led to frequent deposits of hoarfrost (see picture below).  The is important because when snow does return, such frost  result in an underlying weak layer that could lead to avalanches.  But we can worry about that later.

6 comments:

ReelWeather said...

Great stuff Cliff--- I know here in Wisconsin (particularly SE Wisconsin) we are WELL below normal for our snowfall totals. We only received our second batch of accumulating snow, both less then 1". Temperatures have all been well above normal...it has been an unusual season thus far.

Elf said...

I'm scared Cliff. Rumor on the street tells of a weary pack of vigilante welders gathering at Copalis Beach.

Some type of sacrifice ritual, the taking down or giving back in attempt to appease mother earth. An offering for the return of winter.

Fixed Carbon said...

Cliff: That damn ridge! Not good news for NorCal. I actually had to water my garlic garden. Ski prospects for Xmas vacation are dimming. People are bailing out of hotel reservations in the Sierra and switching to a bowl game in SD. San Diego and Mexico hotels booming.

blarsen said...

yep alaska is just getting hammered. anchorage has had storm after storm with gusts over 100mph recorded nearby multiple times in the last few weeks. the mountains nearby anchorage have gotten copious amounts of snow. very jealous they're getting all the action and not us.

kdscatt said...

What is the meteorological explanation for this weather pattern ?
I can offer a few theories; this is currently either a neutral or very weak LaNina pattern. There will be a stronger LaNina that occurs next year, per the prediction.

If this is a moderate LaNina currently, which I doubt because unlike last year's respite in LaNina, there is not an abundance of severe weather along the East Coat of the US to sap energy from the polar jet that normally affects our weather during LaNina episodes.

Scott said...

Didn't you go on and on in late 2010 about how La Nina was supposed to affect us only after the first of the year? Why is this a surprise this year then?