Saturday, January 4, 2014

LACK OF SNOW - can we catch up?

It has been an unusually dry start to the wet season...even record breaking for some areas of the western U.S.  Can the Inland NW catch up by early spring.....history says chances are slim

You might not have noticed, but it's been exceedingly dry in the Inland Northwest this winter. The lack of snow is obvious, but we haven't been getting much rain either.  Above is a map of the precipitation deficit across the West for the October through December period.
full article with more pics


from Cliff Mass Weather Blog Dec 27, 2013
Snow is nature's refrigerator.  In fact, in places where snow can fall, record cold temperatures inevitably occur when there is snow cover.  
So why does snow produce cold surface air temperatures?  And remember surface air temperatures are measured at 2 meters above the ground level.
First, snow is highly reflective, allowing it to reflect the warming rays from the sun back to space.

Second, snow is a very good EMITTER of infrared radiation, much better than the atmosphere.  Such emission of infrared radiation to space produces substantial cooling...think of a refrigerator coil at the surface.
OK, so snow prevents the sun's rays from warming and snow cools by emitting infrared radiation.
But there is more  Snow is a good insulator.  The ground and particularly the subsoils can be relatively warm.  So the snow prevents the conduction of heat from below.  That contributes to cooling.
And finally, if air temperatures get above freezing, melting snow stays at 32F until it gone.

TODAY'S BIG WEATHER STORY IS.....a Weekend Cool Down

...of course Lewiston (red bar) will be the mildest
A dry and cool northerly flow is expected through the weekend across the region. Expect temperatures to cool off by 8 to 10 degrees from their Thursday/Friday highs by Sunday. This graph shows the high temperatures recorded at Spokane, Lewiston and Wenatchee on Thursday January 2nd and the forecast high temperatures for Friday, Saturday and Sunday. 

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