Quantitative Precipitation Forecast
Issued by NWS

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FOUS11 KWBC 270839
QPFHSD

PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
439 AM EDT FRI MAR 27 2015

VALID 12Z FRI MAR 27 2015 - 12Z MON MAR 30 2015


DAYS 1 THROUGH 3...

...NORTHEAST...

FORECAST UNCERTAINTY REMAINS HIGH ACROSS LONG ISLAND AND SOUTHERN
NEW ENGLAND SATURDAY INTO EARLY SUNDAY.  SOME OF THE MODELS
CONTINUE TO SHOW AN INVERTED SURFACE TROUGH DEVELOPING TO THE EAST
OF A COLD UPPER TROUGH WHILE THE RESPONSES WITH RESPECT TO
SNOWFALL RANGE FROM SLIGHT TO SIGNIFICANT.  THE UKMET IS FURTHER
WEST...BUT AGREES WITH THE NAM AND GFS THAT THERE IS THE POTENTIAL
FOR SOME LOCALLY HEAVY SNOWS ACROSS PORTIONS OF LONG ISLAND AND
SOUTHERN NEW ENGLAND.  THE ECMWF ON THE OTHER HAND CONTINUES TO
DOWNPLAY THIS POTENTIAL.  ACKNOWLEDGING THE THREAT SHOWN BY THE
NAM/GFS...RAISED AMOUNTS SOME...PARTICULARLY ACROSS EASTERN LONG
ISLAND AND SOUTHEASTERN NEW ENGLAND...HOWEVER CONSISTENT WITH
PREVIOUS ISSUANCES...CHOSE A SOLUTION MORE CONSERVATIVE THAN THOSE
MODELS...RECOGNIZING THAT PREDICTABILITY ACROSS THE REGION REMAINS
RELATIVELY LOW.

...GREAT LAKES...

A WELL-DEFINED SHORTWAVE WILL BRIEFLY SUPPRESS THE LONG STANDING
RIDGE CENTERING OVER WESTERN NORTH AMERICA AS IT MOVES INTO THE
PACIFIC NORTHWEST/BRITISH COLUMBIA FRI NIGHT.  AS IT MOVES EAST
THROUGH THE ROCKIES INTO THE PLAINS...ANY THREAT FOR HEAVY SNOW IS
EXPECTED TO CENTER WELL NORTH INTO CANADA UNTIL SUNDAY WHEN THE
SYSTEM AMPLIFIES AS IT PHASES WITH A NORTHERN STREAM TROUGH
DIGGING OUT OF NORTHERN CANADA...BRINGING THE RAIN/SNOW LINE SOUTH
INTO THE UPPER GREAT LAKES REGION.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT FOR
THE ENTIRE PERIOD.

PEREIRA

$$





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