December 2012: Wet & “Mild”

December capped off one of the simultaneously wettest and driest calendar years for the inland northwest.  Aside from a few sub par numbers in southwestern ID/eastern OR including the Owyhee mountains, where rain gauges are few and far between, the water-year is off to a great soggy start.  Precipitation for river basins derived from SNOTEL data show all basin at or above normal, with some locales +30%.


This has translated into respectable snowpack numbers, particular in the Cascades and Sierra Nevada, and a rather mixed bag for snow water equivalent numbers in the inland northwest.


Aside the recent cold + stable air mass that has kept valley locales colder than mountains during the night + day due the strong inversion and lack of diurnal heating to promote mixing, well-above normal temperatures have been the rule across the region + broader western US.


Using the North American Freezing Level tracker we can take a look at an estimate of Nov-Dec precipitation that fell on days where the average temperature at 2000-m was below 0C across central Idaho.


Fairly lousy efficiency, and rather different from what one sees due west over the Cascades at 2000-m over the two-month period. I can not speak definitely as to why these differences arise other than potentially a lack of pineapple-express type systems that can do a number on the more-maritime snowpack and less so for the inland mountains.

As 2012 ends, we recall the record, or near record dry spell from mid-July through September, and record demolishing precipitation numbers in March and June for parts of the region. A few stations across the northern extent of the domain including Glacier N. P., and Sandpoint ID ended up with their wettest year on record.