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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1844Z May 12, 2014)
 
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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
244 PM EDT MON MAY 12 2014

VALID 00Z TUE MAY 13 2014 - 00Z FRI MAY 16 2014


DAYS 1 THROUGH 3...


...CENTRAL/SOUTHERN ROCKIES...

A STRONG SHORT WAVE DIVING INTO THE BOTTOM OF THE LONG WAVE TROUGH
OVER THE ROCKIES WILL PROVIDE ENOUGH SYNOPTIC SCALE LIFT FOR
SIGNIFICANT LATE SEASON SNOWFALL ACROSS PORTIONS OF THE CENTRAL
AND SOUTHERN ROCKIES...MAINLY ON DAY 1. WHILE THERE WAS GENERALLY
GOOD MODEL AGREEMENT WITH RESPECT TO THE OVERALL SYNOPTIC
SETUP...THERE WERE SOME MODEL DIFFERENCES WITH RESPECT TO THERMAL
AND QPF FIELDS ON DAY 2. BECAUSE OF THIS...THE QPF FIELDS WERE
BASED MAINLY ON THE 12Z ECMWF SOLUTION...WHILE THERMAL FIELDS WERE
BASED MAINLY ON A BLEND OF THE 12Z GFS/06Z GEFS MEAN AND 00Z
ECMWF.

AS THE STRONG SHORT WAVES DIVES INTO THE LONG WAVE TROUGH POSITION
ON DAY 1...IT PROVIDES THE BEST SYNOPTIC SCALE LIFT BETWEEN 06Z
AND 18Z TUE...MAINLY ACROSS SOUTHWEST CO AND NEARBY NORTHERN NM.
MOISTURE MAY END UP BEING THE LIMITING FACTOR...AS PRECIPITABLE
WATER VALUES REMAIN AT OR BELOW 0.25 INCHES. THE LOW LEVEL FLOW
TURNS TO UPSLOPE AS HIGH PRESSURE BUILDS SOUTH ACROSS THE
ROCKIES... HELPING TO FOCUS THE AVAILABLE MOISTURE ON THE HIGHER
TERRAIN IN THE ABOVEMENTIONED AREAS.

THERE IS A MULTI MODEL SIGNAL (LED PRIMARILY BY THE 12Z GFS) THAT
THE SAN JUAN RANGE IN SOUTHWEST CO WILL SEE BETWEEN 6 AND 10
INCHES OF SNOW. THIS IS WELL SUPPORTED BY THE QPF...AS WELL AS
SEVERAL MEMBERS OF THE LATEST ECMWF ENSEMBLE OUTPUT. THE
PROGRESSIVE NATURE OF THE SYSTEM AND LACK OF AVAILABLE MOISTURE
SHOULD LIMIT HIGHER SNOWFALL AMOUNTS ON DAY 1.

THE SHORT WAVE EXITS DURING THE FIRST HALF OF DAY 2. THE 12Z GFS
AND 06Z GEFS SOLUTIONS APPEAR TO HOLD BACK ENOUGH LIFT IN THE MID
LEVELS FOR SNOWFALL ACROSS SOUTHERN CO AND NORTHERN NM ON DAY 2.
THE REMAINDER OF THE FORECAST SUITE SHOWS LITTLE QPF WITH THE
EXITING MID LEVEL SYSTEM...AND GIVEN THE PROGRESSIVE NATURE OF THE
FLOW...THIS SOLUTION FITS BETTER. THE LACK OF MOISTURE APPEARS TO
TRUMP THE REMAINING LIFT...SO ONLY AN INCH OR TWO OF SNOW ID
EXPECTED IN NORTHERN NM ON DAY 2.

LITTLE OR NO SNOW EXPECTED ELSEWHERE IN THE CENTRAL AND SOUTHERN
ROCKIES ON DAY 2. THE 12Z NAM/09Z SREF MEAN SHOW BOUNDARY LAYER
TEMPERATURES COLD ENOUGH FOR SNOW ACROSS EASTERN NM AND PORTIONS
OF NORTH TX. HOWEVER...GIVEN THE LOW LEVEL FLOW AND LACK OF
MOISTURE... THIS SEEMS OVERDONE...AND NO SNOW WAS PLACED IN THESE
AREAS.

LITTLE OR NO SNOW IS EXPECTED ON DAY 3 ACROSS THE REGION.

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

HAYES