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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1551Z Oct 17, 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
1151 AM EDT FRI OCT 17 2014

VALID 12Z MON OCT 20 2014 - 12Z FRI OCT 24 2014

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

WITH RECENT ECMWF/ECMWF MEAN RUNS OFFERING THE BEST COMBINED SOLNS
FOR FEATURES WITHIN THE AMPLIFIED PATTERN OVER THE ERN PACIFIC AND
NORTH AMERICA... THE LATEST UPDATE CONSISTING OF THE 00Z ECMWF
MEAN AND 00Z/17-12/16 ECMWF RUNS YIELDS MINIMAL CONTINUITY CHANGE
FROM PREVIOUS ISSUANCE.

AMONG ENSEMBLE MEANS THE ECMWF MEAN CONTINUES TO BE CLOSEST TO THE
OPERATIONAL MODELS IN REFLECTING THE LIKELY DEPTH OF THE UPR LOW
CLOSING OFF NEAR THE EAST COAST BY DAY 5 WED AND ASSOC SFC LOW
DEVELOPMENT OVER THE WRN ATLC.  AN AVG OF THE PAST TWO ECMWF RUNS
AND THE 00Z ECMWF MEAN REPRESENTS A GOOD INTERMEDIATE SOLN BETWEEN
THE FARTHER SWD 00Z GFS AND NWD 06Z GFS.  BASED ON THE POSN OF THE
FCST UPR LOW IT SEEMS REASONABLE FOR THE SFC LOW TO WRAP BACK
FAIRLY CLOSE TO THE SRN NEW ENGLAND COAST FOR A PERIOD OF TIME...
EVEN THOUGH SUCH A TRACK IS IN THE NWRN PART OF THE FULL ENSEMBLE
SPREAD.  STILL IT IS WORTH NOTING THAT MOST SOLNS ALOFT ARE WITHIN
TYPICAL ERROR FOR DAYS 5-7 FCSTS.

ONE OF THE MORE CONTENTIOUS ASPECTS OF THE FCST CONTINUES TO BE
THE ULTIMATE EVOLUTION OF ERN PAC ENERGY EXPECTED TO SPLIT ONCE IT
FLOWS INLAND FROM THE WEST COAST.  ASIDE FROM THE CMC... THE
PREVAILING TREND OVER THE PAST 24 HRS HAS BEEN TOWARD A WEAKER/EWD
SOLN WITH WHAT ENERGY REMAINS FROM THE SRN PART OF THE WEST COAST
SHRTWV BUT AS WAS THE CASE YDAY THERE IS A REASONABLE MAJORITY OF
GUIDANCE SUGGESTING THAT THE GFS AND ESPECIALLY THE 06Z RUN IS
UNDERDONE WITH THE AMOUNT OF ENERGY SETTLING OVER THE SRN
ROCKIES/UPR RIO GRANDE VLY.  HOWEVER EVEN ECMWF ENSEMBLE SPREAD
BECOMES QUITE BROAD BY DAYS 6-7 THU-FRI.

THE 06Z GFS ALSO COMPARES POORLY TO OTHER GUIDANCE WITH FLOW FROM
THE ERN PAC ACROSS THE NRN HALF OF THE WRN-CNTRL CONUS.  AMONG
REMAINING SOLNS THERE IS BETTER AGREEMENT THOUGH BY LATE IN THE
PERIOD SUBTLE DIFFS IN W-CNTRL CONUS RIDGING WILL AFFECT THE
DETAILS OF MOIST FLOW IMPACTING THE PAC NW.  THE 00Z ECMWF HAS A
LITTLE MORE RIDGING THAN MOST OTHER SOLNS SO THE INCLUSION OF THE
12Z/16 RUN AND 00Z ECMWF MEAN IN THE FCST HELP TO BRING THE BLEND
CLOSE TO CONSENSUS.

BY NEXT WED-THU THE 00Z/06Z GFS RUNS ARE QUITE FAR NWD RELATIVE TO
OTHER SOLNS... INCLUDING THE GEFS MEAN... WITH SFC LOW PRESSURE
FCST TO BE OVER THE SWRN GULF OF MEXICO EARLY IN THE PERIOD.  THE
GFS HAS HAD SUCH A BIAS OVER THIS REGION THIS YEAR SO PREFER TO
REMAIN WITH THE NON-GFS CONSENSUS HERE.


...SENSIBLE WEATHER HIGHLIGHTS...

UPR LOW CLOSING OFF NEAR THE EAST COAST AND ASSOC WRN ATLC SFC
EVOLUTION WED-FRI WILL BRING A PERIOD OF CHILLY AND BREEZY WEATHER
TO THE ERN STATES ALONG WITH POTENTIAL FOR HVY RNFL MOST LIKELY TO
BE FOCUSED OVER NEW ENGLAND.  PROBABILITIES ARE MODEST AT THIS
TIME BUT HIGHEST ELEVS MAY HAVE SOME POTENTIAL FOR SNOW DURING
PORTIONS OF THE EVENT.  LOCATIONS NEAR THE UPR LOW CENTER MAY SEE
ONE OR MORE DAYS WITH HIGHS AT LEAST 10F BELOW NORMAL.  TRAILING
COLD FRONT EXTENDING INTO THE GULF SHOULD BRING A SHIELD OF SRN
GULF MSTR ACROSS THE FL KEYS/SRN PENINSULA. 
CONSENSUS/CONTINUITY/GFS BIASES CURRENTLY DO NOT FAVOR THE MORE
NWD 06Z/00Z GFS AXIS OF HVY RNFL OVER FL.

FARTHER UPSTREAM THE PREFERRED ECMWF CLUSTER FOR ENERGY SETTLING
INTO THE SRN ROCKIES/UPR RIO GRANDE VLY... COMBINED WITH LOW LVL
UPSLOPE FLOW... MAY PROMOTE PERIODS OF LOCALLY MDT/HVY RNFL OVER
THE SRN ROCKIES/HIGH PLAINS.  WIDE SPREAD AMONG THE FULL SPECTRUM
OF MODEL/ENSEMBLE GUIDANCE CONTINUES TO TEMPER CONFIDENCE THOUGH. 
OVER THE NORTHWEST EXPECT ONE EVENT TO TAPER OFF EARLY IN THE
PERIOD FOLLOWED BY A MORE FOCUSED STREAM OF MSTR IMPACTING THE PAC
NW MID-LATE WEEK.  SWD EXTENT OF HEAVIEST RNFL WILL BE SENSITIVE
TO EXACT ORIENTATION OF FLOW ALOFT.  ASIDE FROM A BRIEF COOLDOWN
AROUND MIDWEEK... EXPECT WELL ABOVE NORMAL TEMPS FROM PARTS OF THE
INTERIOR WEST THROUGH THE NRN PLAINS WITH ONE OR MORE DAYS OF PLUS
10-20F ANOMALIES.  DAILY RECORDS FOR HIGHS/WARM LOWS MAY BE PSBL
AT SOME LOCATIONS DEPENDING ON THE PARTICULAR CALENDAR DAY AND
PERIOD OF RECORD.

RAUSCH