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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0720Z Apr 15, 2014)
 
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
320 AM EDT TUE APR 15 2014

VALID 12Z TUE APR 15 2014 - 12Z FRI APR 18 2014

DAY 1...

...EASTERN OHIO/APPALACHIANS/INTERIOR AND NORTHERN NORTHEAST...

A DEEP TROUGH WILL LIFT NORTHEASTWARD ON TUESDAY IN ASSOCIATION
WITH A STRONG COLD FRONT ALONG THE EAST COAST.  STRONG COLD AIR
ADVECTION BEHIND THE FRONT WILL ALLOW RAIN TO MIX WITH AND CHANGE
TO SNOW FOR A RELATIVELY BRIEF TIME BEFORE ENDING FROM THE CENTRAL
APPALACHIANS ACROSS EASTERN OHIO INTO THE INTERIOR AND NORTHERN
SECTIONS OF THE NORTHEAST. SOME OF THE SNOW COULD BE BRIEFLY HEAVY
SUCH THAT THERE IS A LOW PROBABILITY FOR AS MUCH AS 4 INCHES OR
GREATER COULD FALL FROM THE HIGHLANDS OF THE APPALACHIANS
NORTHEASTWARD ACROSS WESTERN PENNSYLVANIA INTO INTERIOR NEW YORK
AND WESTERN AND NORTHERN NEW ENGLAND.

THE BEST CHANCE FOR SIGNIFICANT SNOW IS FOR MODERATE TO PERHAPS
EVEN HIGH PROBABILITIES FROM NEAR THE NORTHEAST
PENNSYLVANIA/SOUTHEASTERN NEW YORK CATSKILLS/POCONOS TO THE HIGHER
ELEVATIONS OF THE ADIRONDACKS AND GREAT MOUNTAINS OF NORTHERN NEW
YORK AND VERMONT. THERE IS ALSO A LOW PROBABILITY OF SOME FREEZING
RAIN/SLEET DURING THE TRANSITION FROM RAIN TO SNOW THAT HAS A LOW
POTENTIAL FOR SIGNIFICANT ACCUMULATIONS OF .25 INCHES OR MORE
ACROSS PARTS OF EASTERN NEW YORK INTO WESTERN NEW ENGLAND...BUT
THE THREAT APPEARS RELATIVELY SMALL. THE PROGRESSIVE NATURE OF
THIS SYSTEM ALLOWS THE THREAT OF MORE SIGNIFICANT FROZEN
PRECIPITATION TO REMAIN RELATIVELY MINIMAL SINCE GENERALLY A
SLOWING AND CUTTING OFF SYSTEM DOES NOT APPEAR LIKELY WHICH COULD
BE A MORE SIGNIFICANT THREAT DURING EARLY TO MID SPRING. 

DAYS 1 TO 2...

...PACIFIC NORTHWEST/NORTHERN AND CENTRAL ROCKIES AND THE UPPER
MISSISSIPPI VALLEY/MIDWEST...

A COUPLE OF UPPER LEVEL WAVE DISTURBANCES WILL MOVE SOUTHEASTWARD
FROM THE WEST COAST ON TUESDAY DAY 1. THE MORE NORTHERN SYSTEM
APPEARS TO BE INITIALLY MORE ENERGETIC AS IT CROSSES THE PACIFIC
NORTHWEST ON TUESDAY AND THEN DROPS SOUTHEASTWARD TOWARD THE
NORTHERN PLAINS BY WEDNESDAY MORNING AND THEN LIFTS NORTHEASTWARD
AND WEAKENS WITHIN A SIGNIFICANT UPPER CONFLUENT ZONE OVER
SOUTHEASTERN CANADA.  WHILE SNOW SHOULD BE TAPERING OFF ACROSS THE
WASHINGTON CASCADES ON TUESDAY...HEAVY SNOW WILL OCCUR OVER
PORTIONS OF NORTHWESTERN MONTANA AS WELL AS ACROSS PARTS OF
SOUTHWESTERN MONTANA OVER THE ABSAROKA RANGE INTO NORTHWESTERN
WYOMING AS WELL AS ACROSS THE BIG HORN MOUNTAINS IN NORTHERN
WYOMING. WHILE VERY HIGH SNOW TOTALS ARE NOT EXPECTED...THE
GREATEST CHANCE FOR SIGNIFICANT SNOW APPEARS TO BE ACROSS
NORTHWESTERN MONTANA...WHERE MOST ACCUMULATIONS WILL BE OF THE 4
TO 8 INCH VARIETY. 

AS THE TROUGH CONTINUES SOUTH AND EASTWARD...A BAND OF LIGHT TO
MODERATE SNOW WILL DEVELOP NORTH AND EAST OF A DEVELOPING SURFACE
LOW THAT WILL TRACK SOUTHEASTWARD FROM WESTERN SASKATCHEWAN ACROSS
SOUTH DAKOTA ON TUESDAY BEFORE LIFTING NORTHEASTWARD TOWARD
WISCONSIN ON THE WEDNESDAY AND FILLING AS IT DOES SO. DESPITE THE
WEAKENING...THE BAND OF SNOW WILL LIKELY ENHANCE WITHIN THE SHARP
BAROCLINIC ZONE AS VERY COLD AIR REMAINS NORTH OF MINNESOTA WHILE
STRONG WARM AIR ADVECTION MOVES IN FROM THE SOUTHWEST.  THE
POTENTIAL FOR HEAVY SNOW EXISTS AS STRONG FRONTOGENESIS APPEARS TO
OCCUR SIMULTANEOUSLY WITH THE DEVELOPING SNOWFALL. HEAVIEST SNOW
IS EXPECTED ACROSS NORTHERN WISCONSIN INTO THE UPPER PENINSULA OF
MICHIGAN WHERE THERE IS A MODERATE TO HIGH PROBABILITY OF 4 TO
GREATER THAN 8 INCHES OF SNOW AND EVEN A LOW PROBABILITY OF
GREATER THAN A FOOT OF SNOW.

A SECOND SHORTWAVE DROPS SOUTHEASTWARD FARTHER SOUTH AND IS
ASSOCIATED WITH A DEVELOPING UPSLOPE PATTERN OVER CENTRAL COLORADO
ESPECIALLY ALONG THE EASTERN FLANKS OF THE ROCKIES AND SAN JUAN
RANGES OVER CENTRAL AND SOUTHERN COLORADO.  THERE IS ALSO A
MODERATE TO HIGH PROBABILITY FOR GREATER THAN 4 TO 8 INCHES OF
SNOW IN THIS REGION...ALSO WITH A LOW PROBABILITY THAT SOME
ACCUMULATIONS WILL EXCEED A FOOT. 

DAY 3...

...PACIFIC NORTHWEST...

ANOTHER SHORT WAVE AND ASSOCIATED COLD FRONT IS EXPECTED TO CROSS
THE PACIFIC NORTHWEST COAST ON THURSDAY AND SNOW LEVELS WILL
LIKELY COME DOWN ESPECIALLY ON THURSDAY NIGHT INTO FRIDAY MORNING
WITH SIGNIFICANT SNOW ESPECIALLY ACROSS THE WASHINGTON CASCADE AND
THE OLYMPIC MOUNTAINS. IN GENERAL...THE FORECASTS WERE MODIFIED
ACCORDING TO A BLEND OF THE 00Z GFS/00Z AND 12Z ECMWF AND THEIR
RESPECTIVE ENSEMBLE MEANS.

THE PROBABILITY OF SIGNIFICANT ICING IS LESS THAN 10 PERCENT ON
DAYS 2 TO 3.

KOCIN