PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
309 AM EDT SUN MAY 12 2013

VALID 12Z SUN MAY 12 2013 - 12Z WED MAY 15 2013

...PACIFIC NORTHWEST...

CURRENT GUIDANCE REMAINS FAIRLY WELL-CLUSTERED IN ALLOWING SNOW
LEVELS TO FALL TO 5000-6000 FEET ACROSS PORTIONS OF THE NORTHERN
CASCADES OF WASHINGTON MONDAY NIGHT...WHILE MODESTLY MOIST UPSLOPE
FLOW DEVELOPS IN THE WAKE OF A SHORTWAVE TROUGH.  GIVEN GOOD MODEL
AGREEMENT...USED 60 PERCENT OF THE NAM/SREF MEAN ALONG WITH 40
PERCENT OF THE COURSER-GRIDDED GFS/ECMWF TO DERIVE LOW
PROBABILITIES OF 4 INCHES OR MORE OF SNOW ACROSS THE NORTHERN
CASCADES.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

JAMES