Wednesday, October 7, 2009

Rain Boots or Snow Boots?

Here is the latest GFS total accumulated precip for next weeks storm.  The Orange is 3-4 inches of liquid up on the crest.  That could mean 3-4 inches of rain or several feet of snow depending on the temps. 

I have been talking about a pattern change coming around mid-month.  The ridge that has been sitting off the West Coast is going to head East & a flatter ridge is going to emerge out around 170w.  This will allow a strong Northern jetstream, juiced by the remnants of a typhoon off the coast of Asia, to come into the West Coast of the U.S.  around Tuesday of next week. 

There are 2 things that are still uncertain: 1) how far down the coast will the jetstream aim moisture, 2) what will the snow levels be.  Models have been back & forth on how far down the coast the bulk of the moisture comes, but are consistent on at least some some moisture making it into the Tahoe area.  This picture is on the extreme end of precip, but it is possible with the strength of the jet if the jet takes aim at Tahoe. 

Secondly, the main low looks like it will stay well to our North keeping us on the warm side throughout as it comes onshore in Southwest Canada.  That combined with the subtropical moisture entrained in the storm, the flat track of the storm, as well as the possibility of tapping additional subtropical moisture should keep snow levels rather high.  Right now it looks like mostly a rain event below 8,000ft, possibly higher.  Our only chance looks to be if a secondary colder low wraps around the main low injecting colder air later in the storm.  Either way this could be a decent precip event for mid-October to start the water year on the right foot.

The ridge tries to rebuild off the coast by the end of the week keeping storms to our North & keeping us warm.  Interesting to note that the analogs still match best with the winter of 51-52 (no winter that big since).  That winter was a weak El Nino & a ridge, not a low sat over the North Pacific & most of the storms came down over the high & were cold.  We'll have to watch for that.  I'm expecting a wet fall for the Northwest then the shift South should start to occur going into the winter.  Still not very impressed with El Nino.  For all those still hyping the El Nino let's remember the winter of 06-07 which was a weak El Nino like we have now & we had 40% of normal snowfall that winter.  I'm leaning towards a big year but lets base that optimism on all the factors not just one.  BA   


Edgewood said...

I'm roofing my house this weekend. Sounds like just in time!

Anonymous said...

How do you feel about the NWS comparing this to the storm of Jan 5-8, 2008?

BA said...

where did you see that? This is an amazingly strong storm for October but I don't know if it is as big as that Jan. storm. That storm produced over 10 feet of snow on the crest. I would like to read what they said, it's definitely interesting

BA said...
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