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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1549Z Oct 22, 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
1149 AM EDT WED OCT 22 2014

VALID 12Z SAT OCT 25 2014 - 12Z WED OCT 29 2014

...OVERVIEW AND PREFERENCES...

THE TREND IN MEAN FLOW TOWARD A LESS AMPLIFIED PATTERN ACROSS THE
CONUS NORMALLY SUGGESTS LOWER PREDICTABILITY IN FCST DETAILS. 
TODAY THERE ARE ADDED UNCERTAINTIES PRESENTED BY THE EXTRATROPICAL
EVOLUTION OF T.S. ANA/PSBL INTERACTION WITH A MID-LATITUDE PACIFIC
SYSTEM NEAR THE START OF NEXT WEEK PLUS UNKNOWN IMPACT FROM
TODAY'S MODEL GUIDANCE RECEIVING LESS THAN THE NORMAL COMPLEMENT
OF SATELLITE DATA.  FOR SPECIFICS OF THE FCST THE 06Z GFS/00Z
ECMWF PROVIDED THE MOST REASONABLE OPERATIONAL INPUT EARLY IN THE
PERIOD WITH NEARLY EVEN WEIGHTING OF THE 06Z GEFS/00Z ECMWF MEANS
INCLUDED WITH THE MODEL FCSTS BY DAY 5 MON.  THE ENSEMBLE MEANS
OFFER THE BEST WAY TO DOWNPLAY LOWER CONFIDENCE MODEL DETAILS BY
DAYS 6-7 TUE-WED.


...GUIDANCE EVALUATION...

ALTHOUGH IT IS NOT OUTSIDE THE FULL ENSEMBLE SPREAD... BY SUN-WED
THE 00Z GFS SEEMS TO HAVE ONE OF THE LESS LIKELY PACIFIC/WRN NOAM
SOLNS ALOFT RESULTING IN ONE OF THE FARTHEST SWD TRACKS FOR THE
EXTRATROPICAL REFLECTION OF ANA.  THERE IS PLENTY OF UNCERTAINTY
IN THE SPECIFICS OF UPSTREAM FLOW AND HOW ANA MAY INTERACT WITH A
SEPARATE SYSTEM TO ITS N BY DAY 4 SUN... BUT A TRACK WITHIN THE
REALM OF THE 06Z GFS/00Z ECMWF AND THEIR RESPECTIVE ENSEMBLE MEANS
WOULD APPEAR MORE PLAUSIBLE AT THIS TIME.  WITH SOME DIFFS IN
STRENGTH/POSN THE D+8 MULTI-DAY MEANS ARE SUGGESTING A CORE OF
POSITIVE HGT ANOMALIES TO THE S/SW OF ALASKA.  TELECONNECTIONS
RELATIVE TO THIS FEATURE FAVOR A POSITIVELY TILTED TROUGH NEARING
THE PAC NW COAST.  THE 06Z GEFS/00Z ECMWF MEANS LEAD INTO THIS
PATTERN FAIRLY WELL TO PROVIDE A LITTLE MORE CONFIDENCE IN THESE
MEANS VERSUS OTHER PIECES OF GUIDANCE.

LATEST CONSENSUS HAS TRENDED SOMEWHAT SLOWER WITH THE UPR TROUGH
FCST TO PROGRESS EWD FROM THE ERN PAC AND GRADUALLY LOSE AMPLITUDE
AS IT HEADS INTO THE DOWNSTREAM RIDGE.  THIS TREND IS ACCEPTED
GIVEN STRONG 00Z/06Z CLUSTERING THAT REFLECTS THIS TREND AND THE
POSSIBILITY THAT ANA'S EVOLUTION COULD LEAD TO MORE AMPLIFICATION
ALOFT THAN REFLECTED IN CURRENT SOLNS.  RECENT DAYS OF GUIDANCE
HAVE REFLECTED SOME DIFFICULTY IN RESOLVING HOW ENERGY EMBEDDED
WITHIN THE CONUS TROUGH WILL BE DISTRIBUTED SO FURTHER CHANGES IN
SFC WAVE/FRONTAL SPEED DETAILS ARE LIKELY.  A SOLN CLOSE TO AN AVG
OF THE 06Z GFS/00Z ECMWF APPEARS REASONABLE FOR AT LEAST SAT-SUN. 
PREFER NEARLY HALF WEIGHTING OF ENSEMBLE MEANS BY MON AND THEN THE
MEANS EXCLUSIVELY THEREAFTER.

ELSEWHERE... A CONSENSUS LOOKS GOOD FOR ENERGY FCST TO CLOSE OFF
AN UPR LOW NEAR OR JUST N OF NRN NEW ENGLAND BY SUN WITH RAPID
PROGRESSION INTO THE CANADIAN MARITIMES.  MEANWHILE THE NATIONAL
HURRICANE CENTER IS ISSUING ADVISORIES ON T.D. NINE WHICH IS
EXPECTED TO TRACK FROM THE BAY OF CAMPECHE INTO THE NWRN
CARIBBEAN.  RIDGING ALOFT BUILDING IN FROM THE EAST MAY SUPPORT A
MORE NWD DRIFT BY DAYS 6-7 BUT SO FAR GFS RUNS HAVE TENDED TO BE
ON THE STRONGER/NWD SIDE OF THE GUIDANCE SPREAD AT THIS TIME FRAME.


...SENSIBLE WEATHER HIGHLIGHTS...

VIGOROUS TROUGH/SFC SYSTEM NEARING THE WEST COAST AS OF EARLY SAT
WILL BRING SOME AREAS OF LOCALLY HVY RNFL TO THE NRN-CNTRL WEST
COAST SAT WITH LESSER MSTR SPREADING INLAND THROUGH THE NRN HALF
OF THE WEST OVER THE FOLLOWING 1-2 DAYS.  AS THIS FEATURE
CONTINUES EWD AN AREA FROM THE CNTRL/S-CNTRL PLAINS NEWD INTO THE
GRTLKS SHOULD BE FAVORED FOR ORGANIZED RNFL DURING A PERIOD CNTRD
AROUND TUE.  ONE OR MORE BANDS OF HEAVIER PCPN IS PSBL WITHIN THIS
AREA DEPENDING ON PRECISE EVOLUTION SFC/ALOFT.  CONTINUE TO EXPECT
WELL ABOVE NORMAL TEMPS AHEAD OF THE SFC FRONT WITH ONE OR MORE
DAYS OF PLUS 10-20F ANOMALIES FROM THE INTERIOR WEST/ROCKIES
THROUGH THE PLAINS AND INTO THE GRTLKS.  AFTER A BRIEF DRYING
TREND IN THE NORTHWEST ON MON... MSTR AND POTENTIAL FOR SOME HVY
RNFL WILL RETURN TO THE PAC NW AHEAD OF THE EXTRATROPICAL
EVOLUTION OF ANA OR ITS MERGER WITH A MID-LATITUDE PAC SYSTEM. 
NEAR THE EAST COAST... EXPECT UNSETTLED WEATHER OVER THE NORTHEAST
DURING THE WEEKEND WITH ENERGY ALOFT/SFC FRONT CROSSING THE
REGION.  FLOW ALOFT MAY BEGIN TO BRING SOME DEGREE OF MSTR TOWARD
THE FL PENINSULA LATE IN THE PERIOD.

RAUSCH