FOUS11 KWBC 170709
QPFHSD

Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
309 AM EDT Fri Apr 17 2026

Valid 12Z Fri Apr 17 2026 - 12Z Mon Apr 20 2026

...North and Central Rockies through the Northern Plains... Day 1...

De-ampifying shortwave trough will pivot E/NE across the Central
Rockies and Northern Plains through Saturday morning. Broad ascent
ahead of this trough (through a combination of height falls and
PVA) will interact with modest upper level diffluence within the
RRQ of a meridionally arcing, but weakening, jet streak. At the
surface, a cold front surging eastward will provide additional
ascent through convergence, with mid-level fgen in its wake
providing a focus for heavier precipitation as well.

Moisture will remain elevated through this evening thanks to a
combination of Pacific moisture streaming over the Rockies on broad
SW mid-level flow and southerly flow out of the Gulf lifting into the Plains.

This will result in two axes of precipitation: lingering fgen mixed
rain/snow/freezing rain in the Northern Plains, and continued light
to moderate snow across the Central Rockies. The heaviest snow and
ice in the Northern Plains is expected before 12Z, but residual
light freezing rain/snow through this aftn could result in light
accumulations of snow (less than 2 additional inches) and freezing
rain (less than 0.05 inches) from NW MN through the Arrowhead.
Farther south into the Central Rockies, especially in the higher
elevations of CO including the Park Range and Front Range, WPC
probabilities for 4+ inches of snow remain elevated at 50-70%
through D1 before precip shuts off tonight.

...Upstate New York/Northern New England... Day 3...

A strong cold front will cross from Upstate NY Sunday morning to
well of the Atlantic Coast by Monday morning. A narrow corridor of
robust warm and moist advection ahead of this front will bring
periods of rain to New England, but as the the cold front races
east, temperatures will crash dramatically behind it. While this
front will also cause rapid drying of the column, there appears to
be enough of a residual SW flow in the mid-levels to allow for
anafrontal precipitation to continue, which will fall as snow in
the higher elevations of Upstate NY (in the Adirondacks) as well as
the Greens of VT, Whites of NH, and mountains of interior
western/northern ME. While snowfall accumulations should be
generally modest, a few inches of snowfall is possible as reflected
by WPC probabilities indicating a 10-30% chance of 4+ inches in
these higher elevation regions.

Weiss

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