Wednesday, January 28, 2015

Sad Skiing in the Northwest

We go from blizzards in the northeast to an extraordinary lack of snow in the northwest. Here are the most recent snowpack estimates from the NRCS Snotel sites:

Instead of our booming snowpack we had last year, the Washington and Oregon Cascades are well below normal for this time of year---many locations only have around 25% or less of the snow they usually have.  It improves somewhat as you move east into Montana and Wyoming.  However, despite having little snow, this does NOT mean we've had little precipitation.  Here's the total precipitation percentage of normal for the same sites:
Right at 90-110% for most of Washington and Oregon!  Despite some earlier storms that brought flooding, California hasn't seem much since.  The low snow amounts in the Sierras have a lot to do with low precipitation amounts in general (for the third year in a row....).  But it's a different story up north.  Here in Washington we've had the precipitation---it has just been too warm for it to be snow.

We can look for a baseline to compare against by going to the Storm Prediction Center's new sounding climatology page.  They've basically gone through the entire record of radiosonde (weather balloon) launches over time and computed daily statistics about what various sounding parameters should look like at each site throughout the year.  We're going to look at the 850hPa temperatures from the Quillayute sounding out on the western Washington coast (KUIL).  The 850hPa temperatures give us an idea of what the temperatures have been like in the lowest part of the atmosphere.  Here's what the climatology looks like:

The smooth, solid black line running down the middle is a smoothed mean 850hPa temperature throughout the year.  The golden line above represents the 90th percentile of the 850hPa temperatures and the red lines above that represent the record maximum 850hPa temperature for each day (with the thicker red line a running mean of the daily maximum).  You can see that starting in October the 850hPa temperature is, on average, around 6 Celsius, with it dropping to just below freezing (0 Celsius) by the time we get into December and January.  On average.  I grabbed the actual 850hPa temperatures from KUIL since October 1st and here is what we have:

The solid black line is an estimate of the black mean line in the above climatology. The horizontal blue dotted line is at 0 Celsius and the red dashed line is the average over the past four months.  You can see that since about the beginning of November we've been above average, for the most part.  In fact, even though the mean 850hPa temperature should be about -1 Celsius during January, our January average to date is 4.7 Celsius---5.7 degrees warmer than normal and, notably, above freezing.   In fact, based on the climatology, our average January 850hPa temperatures are close to the 90th percentile in the climatology, with some days actually setting new warm temperature records.  

The long-term forecast has these warm conditions continuing for at least the next few months.  The CFS ensemble has high probabilities of 850hPa temperatures being above normal over the northwest.  Here's their ensemble mean forecast for February-April:
Does not look promising for more snow on the slopes out here!

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