Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
329 AM EST Mon Jan 14 2019

Valid 12Z Mon Jan 14 2019 - 12Z Thu Jan 17 2019


...California/The West...
Days 1-3...

Two shortwave troughs round the trough off the West Coast and move
into CA through Tuesday. As these lows drift east to the central
California coast they encounter the ridge across the western US
which will slow the progression and weaken the low. Deep
southwesterly flow and upper level divergence along the base of
the trough will support widespread precipitation across Southern
California later today through tonight, including locally heavy
snows along the southern coastal ranges and the southern Sierra
above about ft. Day 1 WPC probabilities are moderate to high for 8
inches through these areas. Lighter snow accumulations are
expected farther east into the higher terrain of southern and
central Nevada and southern Utah.

The second system shifts into the northern CA coast late Tuesday
which along with an approaching upstream wave will focus snows
further to the north along the Sierra and into portions of the
southern Cascades and Klamath ranges Tuesday night. The main low
then approaches the OR coast Wednesday night with tropically
sourced moisture entering CA/south of the low. This elevated
moisture will lead to heavy precipitation and the potential for
over 24 inches of snow in 24 hours through the High Sierra with
other high elevation snows across the Intermountain West through
Wednesday night.


...Great Lakes...
Days 1-3...

Continued shortwave activity around a sprawling low over Hudson
Bay will bring repeating cold air, forcing and westerly winds
across the Great Lakes producing localized lake effect snow in
typical snow belts in the lee of the Lakes. Moderate WPC
probabilities are limited to the 2 inch range in 24 hrs with
several inches possible through the three days of the forecast
period.


Jackson