Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
427 PM EDT Tue Oct 15 2019

Valid 00Z Wed Oct 16 2019 - 00Z Sat Oct 19 2019

...Pacific Northwest to the northern Rockies...
Days 1-3...
Amplifying southwesterly flow ahead of an approaching trough will
support strong moisture transport into the Pacific Northwest on
Wednesday.  Ahead of the trough, rising snow levels will confine
significant accumulations to the higher peaks of the northern
Cascades through Wednesday afternoon.  By Wednesday evening, as
the upper trough moves inland, snow elevations decreasing to
around 5000ft will support more widespread areas of heavy snow
across the northern Cascades and Olympics.  As the upper trough
continues to moves east, areas of heavy snow are expected to
spread into the northeastern Oregon, northern Idaho, western
Montana and western Wyoming ranges - where snow levels are
forecast to drop to 5000-6000ft Thursday and Friday.  Meanwhile,
mountains snows will continue across western Washington into
Friday, with upstream energy bringing additional moisture and
lower snow levels to the region.  This will likely push three day
snow totals well above 2ft across the higher peaks of the northern
Cascades.  

...Northeast...
Days 2-3...
A powerful cyclone is expected to develop over the Mid-Atlantic
coastal waters Wednesday and move into eastern New England while
rapidly intensifying. Cold air is delayed until Thursday with
sub-zero 850mb temps over interior New England and the Adirondacks
where the snow level reaches 4000ft by late Thursday.  The higher
elevations of the Adirondacks, Green and White Mountains have
potential to change from rain to snow after the cold air arrives,
with several inches possible due to slow movement of the upper
low.
Lower elevations are forecast to remain as mostly rain.

...Central Appalachians...
Days 2-3...
Northwest flow will support upslope precipitation into the central
Appalachians Wednesday night into Thursday.  Snow levels are
expected to decrease to around 3500ft - allowing for an inch or
two of accumulating snow across the higher peaks of the
Alleghenies in West Virginia.

The probability of significant icing is less than 10 percent Days
1-3.

Pereira