Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
353 PM EDT Wed Oct 16 2019

Valid 00Z Thu Oct 17 2019 - 00Z Sun Oct 20 2019

...Pacific Northwest to the Northern Rockies...

Days 1-3...

As precipitation continues, snow levels will drop significantly as
a well-defined shortwave moves inland Wednesday evening and
overnight.  Snow levels lowering to around 5000ft will support
more widespread coverage of heavy snows along the northern
Cascades late Wednesday into early Thursday.  Persistent onshore
flow with embedded mid to upper level waves will likely bring
additional rounds of organized precipitation through Thursday
while snow levels remain between 5000-6000ft across the northern
Cascades and Olympics.  Shortwave ridging will support a relative
lull early Friday before the next wave approaches and moves into
the Pacific Northwest Friday night into Saturday.  This will
deliver another round of moderate to locally heavy precipitation
as snow levels across the Olympics and northern Cascades drop to
4000-5000ft on Saturday.  Three day snowfall accumulations of
2-4ft, with locally higher amounts, are expected across the higher
peaks of the northern Cascades.  Meanwhile father to the east,
snow levels will drop to 4500-5500ft - supporting locally heavy
accumulations across the northeastern Oregon into the central
Idaho ranges on Saturday.

...Northeast...

Days 1-2...
A powerful cyclone is expected to develop over the Mid-Atlantic
coastal waters Wednesday evening and rapidly intensify as it moves
north into eastern New England Wednesday night. Cold air is
delayed until Thursday with sub-zero 850mb temps over interior New
England, with snow levels gradually dropping Thursday.  The higher
elevations of the Adirondacks, Green and White Mountains have the
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 1-2...
Northwest flow will support upslope precipitation into the central
Appalachians Wednesday night into Thursday.  Cold advection lower
snow level enough so an inch or two of accumulating snow is
expected across the higher peaks of the Alleghenies in West
Virginia.

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

Pereira