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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1552Z Oct 18, 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
1152 AM EDT SAT OCT 18 2014

VALID 12Z TUE OCT 21 2014 - 12Z SAT OCT 25 2014

...OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES...

THE LARGE SCALE PATTERN WILL FEATURE A BROAD BUT GRADUALLY
SHARPENING ERN PACIFIC TROUGH WHILE AN EAST COAST UPR LOW SHOULD
BEGIN TO EJECT NEWD ONCE FLOW ROUNDING THE NRN PERIPHERY OF A
STRONG SWRN INTO CNTRL CONUS MEAN RIDGE APPROACHES.  GIVEN TYPICAL
ERROR AT THE TIME FRAME INVOLVED THERE IS DECENT GUIDANCE
AGREEMENT IN PRINCIPLE ALONG THE EAST AND WEST COASTS BUT
SIGNIFICANT SPREAD/TRENDS PERSIST WITH INITIAL WRN CONUS ENERGY
TRACKING INTO THE PLAINS.


ALONG THE WEST COAST THE PRIMARY ISSUE OVER THE PAST DAY OR SO HAS
BEEN THE PRECISE ORIENTATION OF FLOW ALOFT BY DAYS 5-7 THU-SAT...
WHICH WILL AFFECT THE SWD EXTENT OF MSTR REACHING THE PAC NW. 
TRENDS OF THE 06Z GFS/GEFS MEAN AND 00Z CMC ARE TOWARD RECENT
ECMWF/ECMWF MEAN RUNS THAT HAVE SHOWN GREATER NWWD EXTENT OF THE
SWRN INTO CNTRL CONUS RIDGE THUS GIVING UPR FLOW ALONG THE WEST
COAST A LITTLE MORE OF A SRLY COMPONENT.  THE DEVELOPING CLUSTER
YIELDS A RNFL AXIS TOWARD THE MIDDLE-NRN HALF OF YDAYS SPREAD.

WHILE ECMWF BASED GUIDANCE SEEMS TO BE LEADING THE TRENDS OVER THE
NORTHWEST... STRENGTHENING OF A DEVELOPING UPR HIGH OVER THE SWRN
STATES HAS RESULTED IN THE ECMWF/EC MEAN AND SOME OTHER SOLNS
TRENDING IN SOME WAYS TOWARD THE GENERALLY MORE PROGRESSIVE
GFS/GEFS SOLNS FOR INITIAL WRN CONUS ENERGY REACHING THE PLAINS. 
SPREAD WITH EXACT DETAILS ALOFT IS STILL CONSIDERABLE AND GUIDANCE
TYPICALLY HAS DIFFICULTY WITH WEAK ENERGY FILTERING THROUGH MEAN
RIDGES SO CONFIDENCE IN ANY PARTICULAR SCENARIO IS STILL LOWER
THAN DESIRED.

WITH THE EAST COAST UPR LOW/WRN ATLC SFC EVOLUTION... THUS FAR THE
ECMWF MEAN HAS OFFERED THE MOST STABLE SOLN.  GEFS MEANS HAVE
TENDED TO BE ON THE WEAKER SIDE OF CONSENSUS THOUGH THE 06Z
VERSION IS REASONABLY CLOSE TO THE 00Z ECMWF MEAN.  FROM THU
ONWARD THERE ARE INDICATIONS FROM OPERATIONAL GFS/ECMWF RUNS THAT
THE UPR LOW COULD BE A LITTLE DEEPER THAN THE MEANS.  TYPICAL
VARIABILITY IN DETAILS BETWEEN CYCLES WOULD FAVOR INCLUSION OF AT
LEAST TWO RUNS TO CAPTURE OPERATIONAL IDEAS.  UPR LOW POSN STILL
OFFERS POTENTIAL FOR THE SFC LOW TO BE IN THE NWRN HALF OF THE
ENSEMBLE SPREAD FOR AT LEAST A PERIOD OF TIME.

CONSIDERATIONS FOR THE PRIMARY FEATURES OF INTEREST LEAD TO
FAVORING THE 00Z ECMWF MEAN AND 00Z/18-12Z/17 ECMWF RUNS FOR DAYS
3-4 TUE-WED... WITH SOME 06Z GEFS MEAN ALSO INCLUDED DAYS 5-6
THU-FRI BEFORE OPERATIONAL ECMWF DETAILS DIVERGE ENOUGH TO
RECOMMEND A BLEND OF 06Z GEFS/00Z ECMWF MEANS EXCLUSIVELY BY DAY 7
SAT.


...SENSIBLE WEATHER HIGHLIGHTS...

SYSTEM NEAR THE EAST COAST WILL BRING A PERIOD OF CHILLY AND
BREEZY CONDITIONS TO THE ERN STATES ALONG WITH POTENTIAL FOR
CONSIDERABLE RNFL ACCUMULATIONS OVER NEW ENGLAND DUE IN PART TO
SLOW MOVEMENT OF THE LOW SFC/ALOFT.  IT IS PSBL THAT SOME
LOCATIONS NEAR THE NEW ENG COAST COULD SEE SEVERAL INCHES OF RAIN
OVER THE FULL FCST PERIOD.  THE SFC FRONT TRAILING INTO THE GULF
WILL HELP TO PULL ABUNDANT MSTR ACROSS THE FL KEYS/EXTREME SRN
PENINSULA.  WHILE TRENDING SWD THE 00Z/06Z GFS RUNS MAY STILL BE
BRINGING THE RNFL SHIELD TOO FAR NWD.  HEAVIEST RNFL OVER THE PAC
NW SHOULD BE OVER THE OLYMPICS/VANCOUVER ISLAND WITH MEANINGFUL
AMTS EXTENDING AT LEAST AS FAR SWD AS THE NRN OR COAST.  MEANWHILE
INITIAL WRN CONUS ENERGY REACHING THE PLAINS WILL ENCOURAGE A
PERIOD OF RNFL OVER THE CNTRL-SRN ROCKIES INTO THE PLAINS BEFORE
DISSIPATING LATE NEXT WEEK.  BY NEXT SAT MUCH OF THE LOWER 48
SHOULD BE FAIRLY DRY.  THE LARGE SCALE PATTERN WILL FAVOR WELL
ABOVE NORMAL TEMPS OVER/NEAR THE NRN PLAINS WITH STRENGTHENING
INTERIOR WEST-PLAINS RIDGING ALOFT HELPING TO WARM MUCH OF THE
WEST/NRN-CNTRL ROCKIES BY THU-SAT AS WELL.  EACH DAY SHOULD
FEATURE SOME PLUS 10-20F ANOMALIES AND LOCALLY HIGHER VALUES ARE
POSSIBLE OVER THE NRN HIGH PLAINS DAY 3 TUE.  TEMPS AT SOME
LOCATIONS MAY APPROACH/REACH DAILY RECORD VALUES.

RAUSCH