Greetings!

The last of the snow very rapidly disapeared from the Snotel pillow at C1, 
Niwot Ridge on May 29, 2003. This departure was hastened by the very hot 
weather of this week.

What a difference one week can make! Last week ice was coating everything 
at C1, and the snowpack appeared to have stopped melting. This week, it was 
melting at a rate of feet per day. The streams are over bank full, and soon 
there will be no more snow to melt. The ground is drying quickly in many 
places, suggesting if this weather continues, we will be relying upon summer 
convective storms to keep the soil moist and the vegetation green.

The table at the end of this message, courtesy of Tim Bardsley, Snow Hydrologist, 
NRCS, Salt Lake City, provides an historical perspective of meltout dates, as well 
as a prediction of this years date, which might have been exactly correct if 
temperatures had not become so extremely high.

Since 1981, the 2003 SWE of 15.8 inches was 8th highest compared to a mean of 
14.3 inches. It took 51 days to melt out, from peak accumulation date, compared 
to an average of 40 days, and meltout was 15 days earlier than average.

The hot weather of this week took its toll on the snowpack in the S Platte basin 
as well, knocking it from first to second place in the state, but just barely. 
The Laramie/N Platte basin ranks first with 89% of average SWE (the S Platte has 
85% on May 29th).

The Upper Rio Grande is still at the bottom, with esentially no snowpack left at 
the Snotel measuring sites, and the San Juan, Dolores, San Miguel, Animas basins 
rank second to lowest with 15% of average SWE.

The cummulative winter precipitation percentages are much higher in all these 
locations, indicating there is much less water sequestered in the snowpack 
than average (the SWE/PPT ratio is less than one) at this time.

In the western US, snowpacks are lowest, and well below average in Alaska, 
Arizona, and New Mexico, but winter precipitation is much closer to average. 
Snowpack is at or above average, and SWE/PPT ratios near or greater than one, 
in California, Idaho, Montana, and Nevada. The remainder of the states rank in 
between.

So, until next snow season, let us hope for plentiful summer rains to maintain 
any gains in the recovery from drought that this winter has brought many, but 
not all, areas.

Cheers! Mark



Prediction of SWE Melt Rate for NIWOT - Using Linear Regression of Historic Data                                                                      
                                                                        
Water Peak SWE  Peak Date   Melt-Out Date  # of Days Melt Rate  Peak Day (1=Oct1)                       
Year
2003    15.8    04/08/03        06/02/03*       55*     0.29    190*                    
2002    7.0     03/28/02        05/01/02        34      0.21    179             
2001    9.8     04/24/01        05/24/01        30      0.33    206     
2000    12.5    04/05/00        05/17/00        42      0.30    188             
1999    14.7    05/04/99        06/05/99        32      0.46    216     
1998    15.2    04/29/98        06/03/98        35      0.43    211             
1997    20.4    05/03/97        06/18/97        46      0.44    215     
1996    20.6    04/08/96        05/23/96        45      0.46    191             
1995    18.1    05/31/95        06/24/95        24      0.75    243             
1994    15.5    04/16/94        05/25/94        39      0.40    198             
1993    15.9    04/21/93        05/28/93        37      0.43    203             
1992    12.6    04/01/92        05/16/92        45      0.28    184     
1991    9.4     04/01/91        05/29/91        58      0.16    183             
1990    15.3    04/14/90        06/04/90        51      0.30    196
1989    10.8    04/13/89        05/21/89        38      0.28    195
1988    14.0    03/31/88        05/27/88        57      0.25    183
1987    11.9    04/14/87        05/18/87        34      0.35    196
1986    16.8    04/19/86        06/04/86        46      0.37    201
1985    10.9    04/06/85        05/23/85        47      0.23    188
1984    21.1    05/08/84        06/02/84        25      0.84    221
1983    18.3    05/21/83        06/24/83        34      0.54    233
1982    15.1    04/16/82        06/11/82        56      0.27    198
1981    7.6     04/09/81        05/09/81        30      0.25    191
* = predicted

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