Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
429 PM EDT Sun Mar 08 2020

Valid 00Z Mon Mar 09 2020 - 00Z Thu Mar 12 2020


Days 1-3...

...Western U.S....
The Day 1 period through Monday continues to look relatively quiet
across much of the West with respect to snowfall -- with generally
light accumulations expected from the California mountains to the
northern and central Rockies, where a low-to-mid level front
associated with a Pacific shortwave slides into the region on
Monday.  Then on Tuesday, an approaching upper low will bring
widespread precipitation into Southern California.  Snow levels
ahead of the system are expected to be high, with significant
accumulations forecast mainly above 7000 ft along the southern
Sierra and southern coastal ranges.
Snow levels lower on Wed as the low approaches, with heavy snow
likely in the southern CA Sierra Nevada, and possible in the
highest portions of the San Bernardino and San Gabriel Mountains
of southern CA.  Lift is supported by difluent flow in the left
exit region of a 90-110 kt 300 mb jet max crossing southern CA, in
conjunction with 700 mb moisture advection and bands of
convergence. The models have come in better agreement on the
system's timing, with the GFS slowing down to joining the dominant
cluster of solutions.

...Northern Maine...
A cold front dropping south through Maine is expected to stall
tomorrow, and then return north as a warm front on Tuesday. 
Models show light overrunning snows moving east across northern
Maine on Monday. Monday night to early Tuesday, a wave of low
pressure moves east and crosses northern Maine Tuesday night.  A
period of snow is expected across northern Maine, with mid level
warm advection and convergence.  The warming presents a risk for
snow changing over to sleet/freezing rain and then rain. 
Consequently, the greatest risk for heavy amounts is on the
northern border with Canada.  The models/ensemble means cluster
well on the axis/amounts of snow and freezing rain.

The probability of greater than 0.25 inches of icing is less than
10 percent.

Petersen