March 2012 brought record setting precipitation across the northern tier of the inland northwest. This was small potatoes compared to the national climate story of the warmest March in the continental US on record. March 2013 was dry across the inland northwest with most locations receiving less than 2/3rds their normal March precipitation totals. The continental US was somewhat cooler than normal thanks in part to an extreme negative phase of the Arctic Oscillation that is like an exchange program for midlatitude and polar air masses that displaces Arctic air southward while warmer midlatitude air heads poleward.
Temperatures in the region were near normal; however, the last few days of March featured daytime highs over 15F above “normal” coupled with ample sunshine. Shangri-La like conditions the last day of March with high temperatures in the upper-60s to mid-70s across much of the inland northwest outside of the higher elevations was Nature’s little teaser of what spring could be like in the region. Oh what potential, but of course April Fools day ensues and we are back to reality.
This combination has helped give the “green light” to a host of species to return from their winter dormancy. The SNOTEL station that we’ve been tracking this year, Bogus Basin Idaho, located in the Boise National Forest also received the green light as well (to melt, that is). Warm temperatures the last week or so, including overnight lows remaining above freezing, in conjunction with high sun angles, have begun the melt. Bogus Basin had a downright lame showing during WY 2012-13 setting its record for lowest 1 April SWE at 13.1″, over 11″ below the 2000-2012 average, and more than 4″ less than the previous low set in the drought year of 2001. Due to the tight clustering of snowfall forecasts for Moscow in our snowcast 2013, we’ll let April play out before crowning the winner. But clearly, Bogus Basin ski report was not the winner.
Across the western US, current SWE numbers are subpar across the board, outside of locations on the western slopes of the Washington Cascades and Olympics. The particularly low snowpack numbers across southeastern Oregon, through the Owyhees and into the Boise Front Range are certainly a product of an unfavorable stretch of weather conditions the past three months. However, the unusually dry conditions stretching well back into this past summer across southeastern Oregon, in addition to large wildfires (e.g., Long Draw, > 500,000 acres) may have primed soils for flight and are hypothesized to have contributed to a widespread dust-on-snow event in early March. The advection of dust onto snowpack results in a darkening of the snow and increases the amount of solar radiation absorbed by the snowpack, hastening the rate of melt. These sort of events have been frequent in recent years in SW Colorado due to the combination of drought and land-use changes upwind in the desert SW. I am unaware of a chronology of dust-on-snow events in the inland northwest however, though I would speculate they are rare given the frequency of moisture producing systems that keep soils from becoming airborne during our snow season.
Things could be a lot worse however. California had it’s driest start to a calendar year since at least 1895, and that record dry extends up the coast range of Oregon and eastern slopes of the Cascades. While precipitation in California begins dropping off rapidly into April and May, those two months are among the wettest in parts of the eastern extent of the inland northwest providing us with some optimism for water concerns.