Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
421 AM EDT Tue May 14 2019

Valid 12Z Tue May 14 2019 - 12Z Fri May 17 2019


...Northeast...

As an anomalously deep upper low continues to move across the
region and a deepening coastal low tracks north through the Gulf
of Maine, snows are expected to continue across portions of the
northern White Mountains, with rain changing to snow farther
northeast across northern Maine Tuesday evening into the
overnight.  Overall, expect additional accumulations to be limited
to a few inches on grassy surfaces, with WPC guidance only
indicating a Slight Risk for accumulations of 4-inches or more
across portions of northern Maine during the Day 1 period (ending
12Z Wednesday).

...Western U.S....

Significant snow accumulations are forecast to return to the
Sierra as an anomalously deep upper low moves across northern
California on Thursday.  By midday Thursday, the GFS shows 500mb
heights more than 2 standard deviations below normal shifting east
across California into Nevada.  Snow levels which are expected to
be high at the onset of precipitation will drop notably across the
Sierra into the Great Basin as the system moves onshore.  Heavy
accumulations are probable for portions of the Sierra, with WPC
guidance showing a Moderate Risk for accumulations of a foot or
more for areas above 7000 ft during the Day 3 period (ending 12Z
Friday).

The probability of significant icing is less than 10 percent.

Pereira