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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0904Z Feb 27, 2015)
 
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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
404 AM EST FRI FEB 27 2015

VALID 12Z FRI FEB 27 2015 - 12Z MON MAR 02 2015

DAYS 1 TO 3...

...PACIFIC NORTHWEST/CALIFORNIA/GREAT BASIN/CENTRAL TO SOUTHERN
ROCKIES...

OVERALL THE MODELS ARE IN GOOD AGREEMENT WITH THE EVOLUTION OF A
POSITIVELY TILTED UPPER TROUGH FORECAST TO DEVELOP AND DROP SLOWLY
TO THE SOUTH ACROSS CA AND THE GREAT BASIN THIS PERIOD.  A MID
LEVEL SHORTWAVE CURRENTLY DROPPING SOUTH INTO THE PACIFIC
NORTHWEST IS FORECAST TO AMPLIFY AS IT DIGS FURTHER TO THE
SOUTH...REACHING NORTHERN CA AND GREAT BASIN BY EARLY SAT.  THIS
SYSTEM IS EXPECTED TO CONTINUE TO DIG SLOWLY TO THE SOUTH ACROSS
CA AND THE GREAT BASIN THROUGH DAY 2 INTO DAY 3...BEFORE SHIFTING
GRADUALLY TO THE EAST LATE IN THE PERIOD.  WHILE LIGHT TO MODERATE
SNOWS ARE EXPECTED TO SHIFT SOUTH ALONG THE CASCADES INTO THE
SIERRA ON DAY 1...A PROLONGED PERIOD OF MODERATE TO HEAVY SNOWS IS
EXPECTED TO CENTER ACROSS THE SAN JUANS IN SOUTHWESTERN CO INTO
NORTH CENTRAL NM.  THE SLOW MOVEMENT OF THE TROUGH WILL ESTABLISH
A PROLONGED PERIOD OF PRONOUNCED MOISTURE ADVECTION INTO THE
REGION...FUELING THE POTENTIAL FOR SEVERAL FEET OF SNOW ACROSS THE
HIGHER PEAKS BY THE END OF THE PERIOD.

...THE SOUTHERN/CENTRAL PLAINS/MID TO UPPER MISSISSIPPI
VALLEY/GREAT LAKES/NORTHEAST...

THE COMBINATION OF SHORTWAVE ENERGY EMANATING FROM THE
SOUTHWESTERN TROUGH AND A DIGGING TROUGH MOVING SOUTH AND EAST
FROM SOUTH CENTRAL CANADA TOWARD THE UPPER MIDWEST WILL PRODUCE AN
EXPANDING AREA OF SNOWFALL SPREADING EASTWARD WITHIN THE SOUTHERLY
FLOW BEHIND THE RETREATING ARCTIC HIGH PRESSURE SYSTEM.  RAPIDLY
BUILDING HEIGHTS ACROSS THE SOUTHEAST US ON DAY 3 WILL HELP CREATE
AN EXPANDING BAROCLINIC ZONE ACROSS THE CENTRAL AND EASTERN US. 
WHILE THERE APPEARS TO BE LITTLE INDICATION THAT A STRONG SURFACE
SYSTEM WILL DEVELOP...SIGNIFICANT QPF WILL DEVELOP WITHIN THIS
BAROCLINIC ZONE AND THE BULK OF THE HEAVIEST PRECIPITATION WILL
FALL AS SNOW WHILE RESIDUAL LOW LEVEL COLD AIR OVER THE SOUTHERN
PLAINS AND OVER THE MID MISSISSIPPI VALLEY AND LOWER OHIO VALLEY
COULD LEAD TO SOME FREEZING RAIN/SLEET. BEGINNING ON DAY 1 THERE
IS A SLIGHT RISK FOR 4-INCHES OR MORE CENTERING ALONG THE TX/OK
BORDER EAST OF THE PANHANDLES.  BY DAY 2...THE POTENTIAL FOR
4-INCHES IS EXPECTED TO INCREASE WITH A MODERATE RISK EXTENDING
FROM EASTERN KS TO CENTRAL IL WHERE LOW LEVEL MOISTURE IS EXPECTED
TO INTERACT WITH A NORTHERN STREAM BOUNDARY.  MID-UPPER LEVEL
DYNAMICS AND FRONTAL FORCING ARE EXPECTED TO INCREASE FURTHER ON
DAY 3...RAISING A HIGH RISK FOR 4-INCHES OR MORE FROM CENTRAL IND
TO UPSTATE NY...WITH A MODERATE RISK FOR 8-INCHES ACROSS PORTIONS
OF EASTERN OH INTO WESTERN PA.

THE PROBABILITY OF 0.25 INCHES OR GREATER ICING IS LESS THAN 10
PERCENT.

PEREIRA