Niwot Ridge LTER Snow Report for Apr 2006
April 30, 2006 Snowpack Report, Niwot Ridge, C-1, Colorado

April was not kind to our snowpack this year. The manual measurements show 6.75 inches, or 51% of average, a steep decline from last month and the entire season, which has been near and mostly above average. This is the second lowest snowpack of record, and the fastest March to April decline on record (excluding 2002 which set drought records that may stand for quite some time!). The mean April snowpack is now virtually the same as that for March, indicating a possible trend towards earlier snowpack melting at C1.

The Snotel data shows C1 snowpack at 7.4”, or 61% of average, and cumulative winter precipitation (ppt) at 89%. Although warmth and reduced precipitation can account for this drop since last month, one must suspect the role of the red dust layer of 15 February which is appearing at the surface in many locations now, because the darker-than-normal albedo can theoretically accelerate snowmelt.

This drastic decline since last month occurred not only for Niwot, but also for Colorado as a whole. The South Platte basin shows 83% and 96% (snowpack SWE and ppt, respectively), the first time it has been below 107% all season. The state of Colorado is also below near normal conditions for the first time this season, at 69% and 95%. The highest snowpack is in the Laramie/North Platte (88% and 104%, SWE and ppt, respectively), and lowest is still the Upper Rio Grande with 47% and 80%. The southwest Colorado was least effected by this months downturn, due in part to a shift in the storm track that favored this area in April. However, it was also the lowest in the state to begin with. Wolf Creek however, is near its seasonal high with 70% SWE and 84% ppt.

So, the snowpack pattern for the western US is continuing to look very much like a La Nina pattern, as it has all winter, but Colorado is now swept into the dry conditions that had plagued only Arizona and New Mexico. Eastern Wyoming is also suffering, but otherwise snowpack is near to very much above normal in the western US. The highest snowpacks are found in the California Great Basin area, with 171% SWE and 150% ppt. The lowest are in Arizona, which has no snowpack and only 37% ppt. In the major river basins, the Great Basin and Columbia both have Snowpack Indices (SI) greater than one and snowpacks of 136% and 118%, respectively. The lower Colorado basin has no snowpack and 48% ppt while this river basin as a whole shows 75% SWE and 93% ppt.

So, while this snow season had looked quite healthy for Colorado, it is looking like an early meltout and summer, suggesting a dry summer and long fire season.

May can deliver significant snow fall, but this may be a faint hope in light of the NOAA Climate Prediction Center’s forecast of continued weak La Nina conditions through the end of 2006.

More in two weeks! 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     6.75

     Average   5.418    7.842    10.212   12.922   12.99