During the afternoon of Monday, 29 January 2001 numerous snowrollers
developed in the farm fields adjacent to the CSU-CHILL radar site.
(This site is along the western boundary of the Greeley - Weld County Airport
(GXY)). Six to eight inches of new snow had fallen over the
preceding weekend. The rollers apparently developed when increasing
northwest surface winds began to blow over the snow field on Monday afternoon.
The first photograph includes a one gallon can as
a size reference. The trail left by the developing roller is also
visible. This picture was taken shortly before 2:12 MST. At
this time, a middle level cloud layer blocked the sunlight and reduced
the contrast in the picture.
The associated GXY automated surface weather observation was:
1412 MST: wind from 310 deg at 22 gusting to 26 knots, visibility 10
sm, ceiling 7000 ft broken, additional broken layer at 8000 ft, temperature
2C, dew point -3C, altimiter 29.51
Snow roller size compared to a one
gallon can
About an hour later, breaks in the clouds allowed the sun to reach
the surface, so some additional pictures were taken. The photography
was finished at 3:18 PM when the GXY observation was:
1518 MST: wind from 310 deg at 17 gusting to 24 knots, visibility 10
sm, scattered clouds at 7000 ft, temperature 3C, dewpoint -4C, altimiter
29.51
NE view of same snowroller with one
gallon can
SE view in the corn field south of
the radar
SW view in the corn field south of
the radar
We left the radar site around 5 PM and drove back to Ft. Collins via
Colorado highway 392. During this trip, snowrollers were visible
in portions of many of the open fields approximately as far west as the
Windsor area.
Pat Kennedy and Dave Brunkow
2 February 2001
