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

Valid 00Z Thu Dec 03 2020 - 00Z Sun Dec 06 2020


...Texas/Oklahoma Panhandle Region/Northwestern
Oklahoma/Southeastern Kansas...
Day 1...
Expect an ongoing deformation band to continue to reorient
east-west along the Kansas-Oklahoma border, with low-to-mid level
frontogenesis and favorable forcing aloft supporting a small area
of moderate to heavy snow through the evening hours.  Several HREF
members indicate snowfall rates of 0.5-1 inch/hr persisting
through 06Z, raising the potential for additional heavy
accumulations across a small area over far southeastern Kansas,
the Oklahoma Pandhandle and the far northwestern Texas Panhandle
into northwestern Oklahoma.  WPC PWPF is showing high
probabilities for additional accumulations of 4-inches or more
after 00Z.  As the the associated low begins to move east,
snowfall is expected to diminish across the region during the
overnight hours.

...Northeast...
Day3...
The upper low impacting the Plains on Day 1 is expected to move
east into the lower Ohio and Tennessee valleys by late Friday. 
Models continue to differ with the timing and degree of phasing
this system will have with a northern stream trough amplifying
over the Great Lakes at that time.  Significant model spread and
poor run-to-run continuity limits confidence in any particular
solution.  For the moment, the the GFS is a relative outlier with
its lack of phasing and suppressed surface low track across the
Mid-Atlantic states and then out to sea on Saturday.  General
consensus of the remaining 12Z global deterministic runs and the
NAM is for a more phased solution, with a deepening surface low
tracking from the Mid-Atlantic to the New England coasts on
Saturday.  While the NAM, ECMWF, UKMET and Canadian all agree on
bringing a low farther north than the GFS, timing and longitudinal
differences evolve, with significant impacts on QPF and snow
accumulations across the Northeast late in the period.  Therefore,
while there appears to be at least some potential for impactful
snow, especially over the higher elevations of central to northern
New England, any details at this point are far from certain. 

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

Pereira