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Extended Forecast Discussion
 
(Latest Discussion - Issued 1542Z Nov 28, 2014)
 
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1042 AM EST FRI NOV 28 2014

VALID 12Z MON DEC 01 2014 - 12Z FRI DEC 05 2014

...HEAVY PRECIPITATION HEADED FOR THE WEST COAST...

MODELS AND ENSEMBLES HAVE CONVERGED ON A MORE COMMON FLOW PATTERN
EVOLTUION NEXT WEEK...BOLSTERING FORECAST CONFIDENCE/TIMING TO
SLIGHTLY ABOVE NORMAL LEVELS.

IN THE SRN STREAM...ERN PACIFIC MID-UPPER LEVEL TROUGH ENERGY AND
WELL ORGAINZIED SURFACE SYSTEM/HEAVY PCPN TRANSLATION TO THE WRN
US SEEMS MORE ON TRACK. WPC ADJUSTMENT FROM AN SIMPLE GUIDANCE
COMPOSITE IS MORE MINOR COMPARED TO THE LAST FEW DAYS...BUT WATER
VAPOR IMAGERY AND UPSTREAM FLOW STILL SEEM TO BETTER SUPPORT
PROGRESSION ON THE SLOWER SIDE OF NOW BETTER CLUSTERED GUIDANCE.
GIVEN LINGERING UNCERTAINTY AND RECENT PAST RUN TO RUN ISSUES
THOUGH...PREFER AN ENSEMBLE MEAN FORECAST APPROACH AND YESTERDAYS
12 UTC ECMWF ENSEMBLE MEAN FITS THAT SLIGHTLY BETTER THAN OTHER
ENSEMBLE SYSTEM CHOICES WHILE MAINTAINING MAX WPC CONTINUITY.

IN THE NRN STREAM...DEEP EXTRATROPICAL LOW DEVELOPMENT FROM THE
BERING SEA INTO GULF OF ALASKA SHOULD CONTINUE TO ACT TO BUILD AN
AMPLIFIED MID-UPPER LEVEL RIDGE DOWNSTREAM. THIS SHOULD BETTER
ALLOW ENERGY AND LOWER ATMOSPHERIC COLD AIR TO DIG TO THE LEE OF
THE RIDGE TO CARVE OUT A GRADUALLY PROGRESSIVE AND AMPLIFYING NWRN
TO N-CENTRAL TO ERN US MID-UPPER LEVEL TROUGH NEXT WEEK...WITH
AMPLE ROOM TO DIG NOW PROVIDED BY A SLOWER INLAND PROGRESSION OF
SRN STREAM PACIFIC SYSTEM ENERGY. YESTERDAYS 12 UTC ECMWF ENSEMBLE
MEAN WAS PRIMARILY USED TO DERIVE WPC SURFACE FRONTS/PRESSURE AND
500 MB PROGS. OF THE ENSEMBLE SYSTEMS...THIS CHOICE OFFERS A BIT
MORE FLOW AMPLITUDE AND BETTER WPC CONTINUITY WHILE STILL ALLOWING
FOR A MORE SUSTAINED PUSH OF COOLING HIGH PRESSURE DOWN ACROSS THE
S-CENTRAL AND ERN US ALONG WITH SOME ENHANCED ERN US CENTERED PCPN
POTENTIAL WITH APPROACH OF A MORE DYNAMICALLY SUPPORTED AND
MOISTURE FOCUSING LEAD FRONTAL SYSTEM.

SCHICHTEL