Niwot Ridge LTER Snow Report for Mar 2006
March 2006 snowfall pattern had similarities and differences to the established pattern of this snow season, in both Colorado and the western US. It was similar in that the northern areas of both Colorado and the western US, continued to have strong snowpacks of average or above, and the southern areas were below. The difference from earlier this season is that the strong zonal flow pattern weakened, and became meridional enough for the southwestern areas to get some badly needed snowfall. The two SW Colorado basins, the Upper Rio Grande and the San Juan/San Miguel/Dolores/Animas, saw a boost of 20-30% over last month after the meridional flows kicked in.

At Niwot (C1), the manually measured snowpack showed 13.25 inches of water (SWE), a depth of 43”, and a density of 32%, on 31 March 2006. The 13.25” SWE is 103% of the long-term average, and exactly the same percent of average reported by the Snotel network. If it had not been for the single massive snowfall in late March 2003, this would be the highest Niwot March snowpack since 1997. The Snowpack Index (SI) is less than one (103% SWE divided by the 111% cumulative winter precipitation to date) at Niwot, but nearly one for the South Platte basin (108% vs 110%), meaning non-precipitation climatic factors effecting snowpack are just about normal (only slightly detrimental to snowpack development).

The State of Colorado, according to the Snotel network, has a snowpack of 96% of average, and seasonal precipitation of 100%, so a SI of just under one. The highest snowpack is in the Upper Colorado basin, with 111% and 114% (SWE and cumulative precipitation, respectively). The lowest is the Upper Rio Grande, with 65% and 79%, respectively. This is a good increase from last months 43% and 63%, particularly since this is near the start of their spring melt out!

In the western US, Oregon and Nevada have the highest snowpacks, with 134%, and both also have SI’s of greater than one. Montana, Utah, and Washington also have SI’s greater than one. This is good news for snowpack development, and a rare occurrence for so many states to be so positive in this regard, compared to the last several years. Of the major river basins, the Colorado, Columbia, and Great Basin Rivers SI’s are also one or greater.

As mentioned above, there was a slight shift in atmospheric flow this month, a little less zonal and more meridional. The ENSO index is still near neutral to slightly La Nina, and likely to stay this way during the next 3-6 months (9 March 2006, NOAA CPC), so ENSO may not explain this seasons precipitation patterns. The weakening of the zonal flow might be an expected feature of spring onset, but it also coincided with the first time in the last three months that the phase of the Madden-Julian Oscillation (MJO) became indefinable, almost to the day. Whatever the reason, it came just in time for our southern areas!

Until next month, Mark

Sno Tel Data  Niwot Ridge, C-1
Snow Water Content (inches)
Values are for the end of given month
except as noted for May and June

     Season     Dec      Jan      Feb      Mar      Apr     May            Jun 
      81/82    4.75     10.5     11.75    15.5     14.9    12.0   (17th)
      82/83    3.63              4.75     12.75     17     11.75  (30th)
      83/84    12.6     13.25     15      18.9     20.75   
      84/85    3.75     6.25      8.5     10.25    8.75
      85/86     6.5      7.5      14      15.38    17.5
      86/87    6.25     8.75     11.25    12.75    11.75
      87/88     6.5      9.1     12.4     15.75    14.5
      88/89     5.5      7.6      11      10.25     5.6
      89/90     6.5     9.25     10.75    16.1     16.5
      90/91      3        5       7.1     9.38      10
      91/92    6.65     6.75      8.5     12.25    10.25
      92/93    5.75     6.75     10.75     14      15.875
      93/94    7.125    9.063    12.25    13.25    13.25     2.5  (18th)
      94/95    2.625    3.925     7.0     10.125   16.75    17.0  (22nd) 12.375(13th) 19.75(30th)
      95/96    7.50     12.00    17.5     20.375   18.75     6.125 (15th)
      96/97    8.75     12.625   15.125   14.625   20.375   18.0   (15th)
      97/98    7.0625   10.0     10.125   12.875   17.25    12.875 (15th)
      98/99    3.25     6.625     8.375    9.125   14.125   14.25  (15th)
      99/2000  3.5      7.5      10.625   12.375    7.625   
      00/2001  4.375    5.375     7.125   10.00     9.125
      01/2002  2.625    4.25      6.19     7.563    0.0
      02/2003  4.00     5.25      8.5     16.75    14.375   11.44 (15th)
      03/2004  2.75     4.813     7.75     7.875   10.125    3.69 (14th)
      04/2005  4.875    7.7       9.5     11.625   12.875   12.25 (15th)
      05/2006  5.625    8.375     9.5     13.25

     Average   5.418    7.842    10.212   12.922   13.25