Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
426 AM EDT Fri Oct 01 2021

Valid 12Z Fri Oct 01 2021 - 12Z Mon Oct 04 2021

...Southern Rockies...
Day 1...

A closed low over the Four Corners will eject northeast into the
Central Plains by Saturday morning. Ascent associated with this
feature will be provided by height falls and PVA, as well as
modest upper diffluence, during a period of deepening mid-level
saturation driving PWs to more than +1 standard deviation above
the climo mean. The overlap of deep layer lift and this increasing
moisture will spread precipitation across the area, which will
manifest as periods of heavy snow as snow levels fall to around
11,000 ft. As the upper low pulls off to the northeast tonight, a
rapid decrease in mid-level moisture should cause the snowfall to
wane, bringing an end to the accumulation. However, before
precipitation winds down, moderate to heavy snowfall is likely.
WPC probabilities are moderate for 6 inches in the highest terrain
northeast of the Santa Fe, NM, with low probabilities for 4 inches
existing across the remaining Sangre De Cristos and highest peaks
of the San Juans and Colorado Rockies.

For Days 1-3, the probability of significant icing (0.25 inch or
more) is less than 10 percent.

Weiss