THE WEATHER PREDICTION CENTER

COLLEGE PARK, MD


PROBABILISTIC HEAVY SNOW AND ICE DISCUSSION




PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
403 AM EDT WED APR 01 2015

VALID 12Z WED APR 01 2015 - 12Z SAT APR 04 2015


DAYS 1-3...

...CENTRAL ROCKIES/HIGH PLAINS THU-FRI...

AN AMPLIFIED SHORTWAVE TROUGH IS FORECAST TO MOVE OUT OF THE
NORTHERN PLAINS AND INTO THE GREAT LAKES...WITH ITS ASSOCIATED
COLD FRONT DROPPING SOUTH INTO THE SOUTHERN PLAINS. 
MEANWHILE...AN UPSTREAM TROUGH IS FORECAST TO DIVE SOUTHEASTWARD
FROM THE NORTHWEST INTO THE GREAT BASIN.  POST-FRONTAL UPSLOPE
FLOW ENHANCED BY A SURFACE LOW MOVING OUT INTO THE CENTRAL
PLAINS...INTERACTING WITH ENHANCED MID-UPPER LEVEL FORCING
AFFORDED IN PART BY LEFT-EXIT REGION JET DYNAMICS IS EXPECTED TO
SUPPORT MODERATE TO HEAVY SNOWS ACROSS PORTIONS OF THE CENTRAL
ROCKIES AND ADJACENT HIGH PLAINS...WITH SEVERAL INCHES POSSIBLE
ACROSS THE SOUTHEASTERN WY AND N-CENTRAL CO RANGES.  THE WPC
FORECAST IS A REFLECTION OF WPC QPF AND THE BLEND OF THE GFS..GEFS
MEAN AND EC ENSEMBLE MEAN THERMAL PROFILES.

...UPPER OH VALLEY/LOWER GREAT LAKES/NORTHEAST SAT...

AFOREMENTIONED SHORTWAVE DIGGING THROUGH THE WEST ON THU-FRI IS
FORECAST TO MOVE THROUGH THE CENTRAL PLAINS FRI AND LIFT THROUGH
THE OH VALLEY FRI NIGHT-EARLY SAT.  AN ASSOCIATED SURFACE LOW IS
EXPECTED TO TRACK THROUGH THE OH VALLEY ON FRI...REACHING THE
NORTHEAST BY SAT MORNING.  A COUPLED UPPER JET ALONG WITH LOW-MID
LEVEL FRONTOGENESIS IS EXPECTED TO SUPPORT WIDESPREAD
PRECIPITATION ACROSS THE UPPER OH VALLEY..LOWER LAKES REGION INTO
NORTHEAST FRI NIGHT INTO EARLY SUN...WITH RAIN CHANGING TO SNOW
ALONG THE WESTERN EDGE OF A DEVELOPING COMMA HEAD.  THIS MAY
RESULT IN SOME ACCUMULATIONS EXCEEDING FOUR INCHES...ESPECIALLY
ACROSS THE HIGHER TERRAIN OF THE ALLEGHENY PLATEAU/MOUNTAINS IN
NORTHWESTERN PA/WESTERN NY AND THE ADIRONDACKS.  WPC AMOUNTS
FOLLOWED A BLEND OF GFS..GEFS MEAN AND EC ENSEMBLE MEAN FOR BOTH
THEIR QPF AND THERMAL PROFILES...DISCOUNTING THE ECMWF WHICH WAS
DEEPER AND FURTHER TO THE NORTHWEST WITH ITS SURFACE LOW TRACK AND
IN TURN PLACED THE POTENTIAL FOR HEAVY SNOW FURTHER TO THE WEST AS
WELL.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT.

PEREIRA





Last Updated: 403 AM EDT WED APR 01 2015