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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0527Z Dec 14, 2014)
 
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Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1227 AM EST SUN DEC 14 2014

VALID 12Z WED DEC 17 2014 - 12Z SUN DEC 21 2014

...WET PATTERN FOR PAC NW AND LOWER MS VALLEY...


...OVERVIEW...

A LONG ARC OF UPPER RIDGING FROM NW OF HAWAII TO CENTRAL CANADA TO
WEST OF SPAIN/PORTUGAL SUPPORTS AN ACTIVE PATTERN ACROSS THE
CONUS. SPLIT FLOW DOWNWIND OF A ROARING PAC JET SUPPORTS TWO
TROUGHS TO PASS THROUGH THE SOUTHWEST CONUS... ONE MIDWEEK AND THE
SECOND ONE LIKELY NEXT WEEKEND. SUBTROPICAL JET OUT OF THE CENTRAL
EAST PACIFIC WILL PLAY AN IMPORTANT ROLE IN HOW THE SYSTEMS EVOLVE
AS THEY TAKE THE SOUTHERN ROUTE FROM WEST TO EAST. NORTHERN STREAM
FLOW WILL BE IMPORTANT AS WELL IN THE EAST WITH REGARD TO HOW
DEVELOPED THE EXITING SYSTEM MAY BE NEXT WEEKEND.


...GUIDANCE PREFERENCES....

BOTH THE 18Z GEFS MEAN AND 12Z ECENS MEAN OFFER GOOD AGREEMENT
THROUGH THE PERIOD... AND A BLEND AMONG THEM WITH THE 18Z PARALLEL
GFS AND THE 12Z ECMWF OFFERED A GOOD STARTING POINT. MAIN WEATHER
SYSTEMS WILL BE THE APPROACHING FRONT INTO THE PAC NW BY FRIDAY...
WHERE THE MODELS ARE REASONABLY CLOSE... AND THEN ALONG THE GULF
COAST FRI-SUN AS THE SOUTHERN STREAM SYSTEM MOVES EASTWARD. BY
NEXT SUNDAY... ENSEMBLES SHOW THE TYPICAL SPREAD WITH AN EAST
COAST SYSTEM WITH THE ECMWF ON THE STRONGER/STRONGEST AND WESTERN
SIDE OF THE SPREAD WITH WEAKER/QUICKER MEMBERS WELL EAST.
PROGRESSIVE FLOW WOULD SEEM TO DISCOUNT THE SLOWEST SOLUTIONS BUT
NEARLY ANYTHING IS GAME RIGHT NOW GIVEN THE LEAD TIME.


...SENSIBLE WEATHER HIGHLIGHTS...

WET CONDITIONS OVER THE PAC NW LATE THIS WEEK AND ALSO OVER THE
LOWER MS VALLEY... FROM E TX/OK EASTWARD. MODERATE TO HEAVY RAIN
WILL BE POSSIBLE GIVEN THE FAVORABLE SETUP/INGREDIENTS -- STRONG
SHORTWAVE... SUBTROPICAL JET... GULF MOISTURE. TEMPERATURES SHOULD
AVERAGE NEAR TO ABOVE NORMAL AMID A PACIFIC-DOMINATED FLOW. BEHIND
THE DEPARTING SYSTEM WEDNESDAY TEMPS IN THE HIGH PLAINS SHOULD BE
A BIT BELOW AVERAGE BEFORE MODERATING IN TIME. ENOUGH COLD AIR MAY
BE IN PLACE IN THE EAST FOR SOME WINTRY PRECIP ON THE NW SIDE OF
THE PRECIP SHIELD NEXT WEEKEND.


FRACASSO