000
FOUS11 KWBC 121942
QPFHSD

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

VALID 00Z MON MAY 13 2013 - 00Z THU MAY 16 2013

...PACIFIC NORTHWEST/NORTHERN ROCKIES...

...DAY ONE...

THE PROBABILITY OF HEAVY SNOW AND/OR SIGNIFICANT ICING IS LESS
THAN 10 PERCENT.

...DAY TWO...
CURRENT GUIDANCE REMAINS FAIRLY WELL-CLUSTERED IN SHOWING A
PROGRESSIVE 700 MB WAVE AND 300 MB JET STREAK ACROSS THE PACIFIC
NORTHWEST AND NORTHERN ROCKIES/HIGH PLAINS.
IN THE VICINITY OF THE WAVE IS EXPECTED TO BE A BURST OF 700 MB
CONVERGENCE AND ASCENT UNDERNEATH 300 MB DIVERGENCE.

DRYING IN THE WAKE OF THE 700 MB WAVE LIMITS POST FRONTAL UPSLOPE
SNOW SHOWERS. THIS COMBINES WITH A 6 HOUR OR LESS DURATION OF 700
MB VERTICAL MOTIONS KEEPS POTENTIAL FOR A HEAVY SNOW EVENT
LIMITED.  GIVEN GOOD MODEL AGREEMENT...USED 09Z SREF MEAN/12Z
GFS/12Z ECMWF QPF/TEMPERATURE PROFILES TO DERIVE LOW TO MODERATE
PROBABILITIES OF 4 INCHES OR MORE OF SNOW ACROSS THE NORTHERN
CASCADES.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.


...DAY THREE...

THE PROBABILITY OF HEAVY SNOW AND/OR SIGNIFICANT ICING IS LESS
THAN 10 PERCENT.


PETERSEN


$$