January 2013 was the coldest month in Boise Idaho since December 1990. However, unlike the cold air outbreak of December 1990 that influenced much of the western US, the coldest air last month was parked in the basins of the Great Basin. Salt Lake City was at the epicenter of cold, having their coldest month since 1949. The anomalously cold air was a byproduct of a decent snowfall event in early January that provided a highly reflective and insulative surface that is great at staying cool, followed by a persistent blocking pattern that (1) kept mid-latitude disturbances well north or south of the western US thereby inhibiting any mixing of air in the boundary level, and (2) allowed temperatures in the lower atmosphere near 10,000ft to get rather “warm” for the heart of winter that helped keep the cold air at lower levels. In such a stable air mass, particularly when solar radiation is laughable as it is in January, cold air gravitates to valley bottoms resulting in an upsidedown atmosphere. Radiative fog persisting in valleys inhibit any sort of daytime heating and opportunity to mix the inversion.
On more than a few occasions during the latter half of January, temperatures at SNOTEL stations in the Blue Mountains of NE Oregon & SE Washington above 4500 feet had daytime highs in the 50s, while 50-miles west and several thousand feet lower, places like Walla Walla only reached the 20s. As the saying goes, if you don’t like the weather (or climate) in the western US, drive 5 miles. In this case, preferably up.
Jim Steenburgh of University of Utah has an awesome “Wasatch Weather Weenies” blog that captured details of this event including the numerous air quality concerns it brought to the Great Basin.
January was a cool month. Nighttime lows were about 10F below normal across the entire Snake River plain. Granted, since most of our long-term observations stations in the inland northwest are situated in valleys and subject to inversions, it is likely that such estimates are not representative of the broader landscape. Looking at a few SNOTELs in the Blue Mountains and Cascades, temperatures in January were at or slightly above normal.
By contrast, no matter how you dissect January, it was dry. Fortunately, Oct-Dec were rather wet and provided a buffer for a sub-par month that has filtered into the first half of February.
Outside of the southern to middle Rockies, nearly all of the western United States SNOTEL basins are on-par for year to date precipitation.
However, current basin SWE numbers are below normal for much of the inland northwest. This is consistent with the relatively warm Nov-Dec when much of that snow actually fell and the cold but dry January. Of course, last year around this time things looked much worse before the great comeback.
2013 Snowcast Challenge Update
23 forecasts were made in November on the total snowfall for Moscow, ID and the 1 April Snow Water Equivalent at the Bogus Basin SNOTEL site. A look at the forecast shows a few outliers who were really hoping for epic skiing conditions or the ability to go hiking (w/o snowshoes) at 6500ft in early April.
As of Feb 11, Moscow received 35″ of snowfall so far this water year (82.5% of normal), and SWE at Bogus Basin is 11.0″ (65% of normal). The latter number is the lowest total observed at Bogus Basin in the 13-year lifespan of the station and nearly 2″ less than the previous lowest SWE year-to-date (2005). BTW, 1 April SWE in 2005 was 78% of normal and the second lowest on record behind the drought year of 2001.
Refining our scope to more reasonable forecasts reveals the following figure.
Observed (2000-2012) Moscow snowfall totals and 1 April SWE from Bogus Basin are shown by magenta circles. There is a reasonable correlation between the two variables for both observations and our collection of predictions. For reference, the 2000-2012 “normal” for 11 Feb is shown in blue. We will track this the next two months. With a continuation of dry conditions for the next week, there will be another substantial deficit to recovery from.