Current Theme: Waterworks
	Snowpack report - Niwot Ridge - February, 2005 Mark Losleben - CU INSTAAR Research Staff

The following snowpack conditions on Niwot Ridge have been reported by Mark Losleben for February 2005. Select here for more information about these snowpack reports

Greetings from Niwot Ridge!

The February snowpack here at C1 dropped a bit from last month, percentage-wise, but is still the highest end-of-February value since 1998.

On 28 February 2005, the snow water equivalent (SWE) at C1 was 9.5 inches, or 92% of average, as measured by hand today. This compares to the Snotel value of 8.8", or 90% of average. The Snotel cumulative winter precipitation at C1 is 11.7", or 107% of average, indicating negative weather conditions that promote snowpack development relative to the long term (warmer, drier winds, etc. The Snowpack Index (SI) of less than one is another way of say this.

Statewide, the pattern begun at the start of the season is continuing: slightly below average in the northern and eastern basins, and well above average in the southern and southwestern basins, giving a statewide average of 112% (104% winter precip). Our South Platte basin has the lowest snowpack, on a percentage basis, at 84%, and a cumulative winter precipitation of 85% (SI essentially 1, or normal). The other northern and eastern basins show similar snowpack levels; 88% and 89% for the Yampa/White, and Laramie/N.Platte, respectively. The San Miguel/San Juan/Animas/Dolores basin has the highest snowpack at 152% (127% cumulative winter precipitation), with the Upper Rio Grande essentially the same (151% and 136%, snow/winter precip, respectively).

Colorado continues to be a microcosm of the western US; wetter southern and drier northern regions, and the SI tends to be less than one in the drier regions and greater than one in the wetter ones. The state of Washington continues to have the lowest snowpack in the western US, reporting only 27% of average (64% winter precip), and Oregon is little better with 37% and 56%, snowpack/winter precip, respectively. Arizona, Utah, the Great Basin sites of California, and New Mexico again have the highest snowpacks: 163%, 141%, 134%, and 132%, respectively, and their SI's are greater than one.

Two comments on current snowpack conditions:

1. The low snowpacks in the Pacific Northwest, where winter temperatures are closer to the freezing level, are consistent with recent predictions of Mote, et al (BAMS vol.86, no. 1, Jan 2005), that such regions will be most susceptible to warming climate conditions. Note that the low snowpack here is well below expected, given their cumulative winter precipitation.
2. This strong El Nino pattern of winter precipitation is unusual given the sea surface temperatures indicating only a very weak El Nino. In fact, NOAA's Climate Prediction Center forecasts the next three months to transition from current weak El Nino to ENSO- neutral conditions (10 Feb report).

There is a hypothesis that El Nino, or La Nina, conditions will be as expected when ENSO and the PDO (Pacific Decadal Oscillation) are in phase, but not when they are out of phase with each other. There is speculation the the PDO is shifting phase right now (but years are often needed to know for sure), which would make it out of phase with ENSO and this current weak El Nino.

Until next month,

Mark Losleben

                      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

     Average   5.409    7.819    10.242   12.964   13.266