Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
348 AM EST Wed Dec 02 2020

Valid 12Z Wed Dec 02 2020 - 12Z Sat Dec 05 2020



...Southern and Central Plains...

The development of a closed low and coupled low level
convergence/high level divergence maxima near a low level front
supports an increase in precipitation today, including a heavy
snow threat from western OK to the eastern OK/TX panhandles, and
possibly across the border nearby in far southern Kansas. Led by
the hi-res guidance, the trend in the 00z models was toward the
QPF and snow a bit further west from prior forecasts. A few high
res runs show potential for a foot of snow, including the NSSL WRF
and WRF ARW, as well as the parent NAM. The global models are
lighter with QPF and snow amounts, including the
ECMWF/GFS/UKMET/Canadian global. 

Snow is expected to develop during the day and continue into
tonight.  Low-to-mid level frontogenesis on the west side of a
developing low moving is expected to support banded precipitation
and potentially heavy snow centered across northwestern Oklahoma
into southern Kansas late today and tonight, ending early
Thursday.  Forecast confidence is limited by
persistent spread with respect to the rain/snow line.  WPC
guidance followed a compromise between the hi-res and warmer
global guidance.  The rain/snow line drifts east into central KS
and OK later today/tonight in tandem with the upper low.  The
longer duration precip as snow leads to higher probabilities in
northwest OK to the TX panhandle border/eastern OK panhandle.

...Great Lakes...
A deep low moving north into Quebec supports the low-mid level
deformation and convergence zone moving north from Lake Erie into
Ontario and Lake Ontario. Snows are expected to gradually diminish
in the lee of Lake Erie.  Snow has developed in the lee of Lake
Ontario. Westerly boundary layer flow persisting this morning
across Lake Ontario will support snow continuing, with locally
heavy amounts possible today across the Tug Hill region. The snow
tapers as dry air aloft advects into the region, ending the snow
this afternoon/evening.

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

Petersen