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Extended Forecast Discussion
 
(Latest Discussion - Issued 1547Z Oct 19, 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
1147 AM EDT SUN OCT 19 2014

VALID 12Z WED OCT 22 2014 - 12Z SUN OCT 26 2014

TRENDS AND INCREASED SPREAD SEEN IN SOME OF THE 00Z-06Z GUIDANCE
HAVE LOWERED CONFIDENCE IN THE FCST FROM THE ERN PACIFIC INTO WRN
NORTH AMERICA DURING THE LATTER HALF OF THE MEDIUM RANGE PERIOD. 
BEYOND THE LATEST GFS/GEFS MEAN RUNS TRENDING FASTER WITH THE
ARRIVAL OF ERN PAC TROUGH ENERGY INTO THE WEST... 00Z
GEFS/ECMWF/CMC ENSEMBLE SPREAD BECOMES QUITE LARGE BY FRI-SUN AND
00Z ECMWF/CMC RUNS ALONG WITH SOME ENSEMBLE MEMBERS RAISE THE
POSSIBILITY THAT ERN PAC TROUGH FLOW COULD SPLIT.  A FURTHER
COMPLEXITY IS UNCERTAINTY OVER THE INTERACTION BETWEEN TROPICAL
CYCLONE ANA AND THE SRN EDGE OF THE PACIFIC WESTERLIES.  D+8
MULTI-DAY MEANS INDICATE THAT POSITIVE HGT ANOMALY CENTERS OVER
THE NERN ATLC AND AT HIGH LATITUDES OF THE ERN HEMISPHERE NEAR 80E
MAY BE PROMINENT WITH BOTH TELECONNECTING TO PROGRESSIVE LOW
AMPLITUDE FLOW OVER THE LOWER 48.  THE FLATTENING TREND OF
UPSTREAM PAC FLOW LATE IN THE PERIOD ALONG WITH
TELECONNECTION-FAVORED FLOW PRECLUDE FULL DISCOUNTING OF A FASTER
ERN PAC TROUGH... BUT CONFIDENCE IS SUFFICIENTLY BELOW AVG TO GIVE
THE 00Z GEFS MEAN ONLY 30 PCT WEIGHTING RELATIVE TO THE 00Z ECMWF
MEAN.

FARTHER EWD A CONSENSUS APPROACH STILL APPEARS BEST FOR THE SYSTEM
FCST TO AFFECT THE NORTHEAST MID-LATE WEEK.  THE INITIAL 70/30
BLEND OF THE 00Z ECMWF MEAN/00Z GEFS MEAN WAS ENHANCED SOMEWHAT TO
ACCOUNT FOR THE BETTER DETAIL OF OPERATIONAL GUIDANCE.  COMPARED
TO PRIOR DAYS THERE IS BETTER AGREEMENT ON A SFC LOW TRACK CLOSER
TO THE SERN NEW ENGLAND COAST... WHICH SEEMS REASONABLE GIVEN THE
UPR LOW TRACK.

GUIDANCE CONTINUES TO HAVE DIFFICULTIES WITH INITIAL
ROCKIES/PLAINS ENERGY THAT SHOULD AMPLIFY DOWNSTREAM FROM A
BUILDING SWRN-CNTRL CONUS RIDGE.  MULTI-DAY TRENDS HAVE BEEN
TOWARD THE FASTER EDGE OF THE ENVELOPE.  THUS FAR ONLY THE
OPERATIONAL ECMWF SHOWS SUCH A DEEP/CLOSED SYSTEM REACHING THE
GULF OF MEXICO SO ITS 00Z RUN THAT PULLS LOWER LATITUDE LOW
PRESSURE INTO THE ERN GULF APPEARS TO BE A LOW PROBABILITY
SCENARIO.  RELATIVE TO THE FULL 00Z ENSEMBLE SPREAD FOR SFC LOWS
THE 00Z ECMWF IS FAIRLY EXTREME THOUGH NOT QUITE TO THE POINT OF
BEING AN OUTLIER.


...SENSIBLE WEATHER HIGHLIGHTS...

SYSTEM AFFECTING THE NORTHEAST WED-FRI SHOULD BRING AREAS OF
ENHANCED RNFL TO PARTS OF NEW ENGLAND ALONG WITH CHILLY/BREEZY
CONDITIONS OVER A LARGER PORTION OF THE EAST.  ERN CONUS TEMPS
SHOULD MODERATE TOWARD NORMAL BY NEXT WEEK THOUGH BREEZY CONDS MAY
PERSIST OVER THE NORTHEAST.  CONTINUE TO EXPECT POTENTIAL FOR HVY
RNFL OVER THE FL KEYS/EXTREME SRN PENINSULA AS DEEP TROPICAL MSTR
INTERACTS WITH THE FRONT TRAILING FROM THE NERN SYSTEM.  THE PAC
NW WILL ALSO SEE ONE OR MORE EPISODES OF MDT-HVY RNFL WITH ONGOING
DETAIL DIFFS IN GUIDANCE LEAVING SOME UNCERTAINTY OVER PRECISE SWD
EXTENT.  IMPACT OF MORE SIGNIFICANT TIMING ISSUES ALOFT OVER THE
ERN PAC/WRN CONUS BECOMES AN ISSUE LATER IN THE PERIOD AS WELL. 
MEANWHILE MULTI-DAY TRENDS TOWARD FASTER PROGRESSION OF WEAK
ROCKIES/PLAINS ENERGY EARLY IN THE PERIOD SHOULD KEEP ASSOC PLAINS
RNFL MOSTLY IN THE LGT-MDT RANGE.  WARMEST TEMPS RELATIVE TO
NORMAL WILL EXTEND FROM THE INTERIOR WEST THROUGH THE NRN PLAINS. 
GREATEST COVERAGE OF PLUS 10-20F ANOMALIES IS LIKELY THU-SAT...
WHEN READINGS COULD APPROACH/REACH DAILY RECORD VALUES AT SOME
LOCATIONS. 

RAUSCH