Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
444 PM EDT Sun Oct 25 2020

Valid 00Z Mon Oct 26 2020 - 00Z Thu Oct 29 2020


...Winter Storm across the central-southern Rockies and
central-southern Plains...
...Heavy snow expected in the ranges of CO/NM and significant
icing is expected in portions of the southern Plains...

An amplifying upper trough will continue to advect cold air south
out of the central Rockies and Plains into the southern Rockies
and Plains, with a widespread winter precipitation event.

The heaviest snows are forecast across the CO/NM Rockies/Sangre De
Cristo Mountains/San Juans, with moderate snow spreading into the
adjacent high Plains. Increasing low level convergence/easterly
flow is expected to help support heavier totals, with WPC PWPF
continuing to show probabilities of 50 percent or greater for
accumulations of 6 inches or more across this region, including
the Denver metro area.

High pressure over the central Plains will help drive the cold air
south across the southern Plains.
The cold air surge is shallow, with developing mid level warm
advection on Monday and Monday night leading
to precipitation and a mixture of sleet and freezing rain across
the southern Plains.
An area of a quarter to four tenths of an inch if ice accumulation
is possible across central to western OK and northwest TX, with
lighter amounts in central to eastern Kansas to the adjacent
portions of northwest MO.

Monday, models show a closed circulation beginning to develop near
the Four Corners region.  Snows are expected to continue across
southern Colorado while extending south into New Mexico, with
heavy accumulations likely across the San Juan and Sangre de
Cristo mountains.  Meanwhile, snows will also begin to develop
farther southwest across the ranges of eastern Arizona, with
significant accumulations possible in the White Mountains.

On Tuesday night-Wednesday, as the closed low ejects east from NM
on to the high Plains, the cold air aloft allows the precip to
change over to snow in eastern NM and possibly into the TX/OK
panhandles.  Further east, the continuing southerly mid level flow
keeps a transition of mixed sleet/freezing rain across the eastern
panhandle of TX/OK into southwest TX. Another round of
sleet/freezing rain accumulations is possible.  With confidence
that an extended period of below freezing temps at the surface,
sleet and freezing rain should be able to accumulate.

We will need to monitor the possibility of an extended period of
icing in portions of northwest Texas/adjacent eastern TX/OK
panhandles. 

Petersen