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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 0620Z Sep 30, 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
220 AM EDT TUE SEP 30 2014

VALID 12Z FRI OCT 03 2014 - 12Z TUE OCT 07 2014

...OVERVIEW...

EXPECT AN AMPLIFIED MEAN TROUGH TO SETTLE OVER THE ERN HALF OF THE
CONUS DOWNSTREAM FROM A STRONG MEAN RIDGE ANCHORED NEAR THE WEST
COAST.  AT LEAST THROUGH DAY 6 MON THE PATTERN SHOULD HAVE FAIRLY
HIGH PREDICTABILITY THOUGH SOME EMBEDDED FEATURES WILL HAVE LOWER
CONFIDENCE.  SPREAD ASSOC WITH COMPLEXITIES OF FLOW FROM THE NRN
PAC NWD MAY TRANSLATE DOWNSTREAM AND BEGIN TO INFLUENCE THE WRN
NOAM FCST BY DAY 7 TUE.


...GUIDANCE EVALUATION/PREFERENCES...

FOR THE FIRST TWO DAYS OVER THE EAST... LATEST GUIDANCE IS
REVERSING SOME OF THE FASTER TRENDS THAT HAD BEEN OBSERVED OVER
THE PAST COUPLE DAYS WITH THE COLD FRONT CROSSING THE REGION.  THE
PREFERRED 18Z GFS/18Z GEFS MEAN/12Z ECMWF MEAN CLUSTER REFLECTS
THE MODESTLY SLOWER TREND FROM PRIOR CYCLE WHILE NEW 00Z SOLNS
THUS FAR ARE GENERALLY AT LEAST AS SLOW.  IN ADDITION LOW PRESSURE
LIFTING AWAY FROM THE UPR GRTLKS ON FRI HAS RETURNED TO A POSN
MORE SIMILAR TO A COUPLE DAYS AGO... VERSUS A FASTER/NWD FCST
YDAY.  THE 12Z ECMWF BECOMES FAIRLY EXTREME RELATIVE TO MOST OTHER
GUIDANCE FOR ITS SRN TRACK OF THE UPR LOW OVER THE GRTLKS AND
SHARPER/SLOWER WITH THE TROUGH TO THE S/SE.  THUS THAT MODEL RUN
IS NOT INCLUDED IN THE BLEND.

BY SUN-TUE PREFER TO LEAN ON THE 18Z GEFS/12Z ECMWF MEANS
EXCLUSIVELY GIVEN DECREASING CONFIDENCE IN PRECISE DETAILS OF FAST
MOVING PAC ENERGY FLOWING INTO THE ERN TROUGH... AND DIFFS
DEVELOPING WITH RESPECT TO HOW QUICKLY THE WRN RIDGE FLATTENS IN
RESPONSE TO UPSTREAM FLOW.  THE CMC MEAN CAN SOMETIMES BE TOO
STRONG WITH ITS RIDGES BUT ITS 12Z VERSION ALONG WITH THE 12Z-18Z
GEFS MEAN DO SUGGEST THE RIDGE WILL NOT FLATTEN QUITE AS QUICKLY
AS IN THE 12Z ECMWF MEAN.  TRENDS FROM YDAY HAVE BEEN TO DELAY
FLATTENING THE RIDGE A LITTLE SO AT LEAST HALF INCLUSION OF THE
GEFS MEAN ALONG WITH THE ECMWF MEAN APPEARS REASONABLE.  FARTHER
EWD THE NATURE OF SUPPORTING MID LVL ENERGY WILL LIKELY RESULT IN
SFC FEATURES THAT HAVE POOR AGREEMENT/RUN TO RUN CONTINUITY IN THE
GUIDANCE.


...SENSIBLE WEATHER HIGHLIGHTS...

THE FRONT CROSSING THE ERN STATES FRI-SAT WILL BE ACCOMPANIED BY
RNFL OF VARYING INTENSITY.  PROGRESSIVE NATURE OF THE FRONT SHOULD
KEEP TOTALS MODERATE AT MOST LOCATIONS THOUGH SOME ENHANCEMENT
FROM ATLC INFLOW IS PSBL OVER NEW ENGLAND.  BEHIND THE FRONT A
LARGE PORTION OF THE LOWER 48 SHOULD BE DRY.  EXCEPTIONS INCLUDE
THE GRTLKS AND VICINITY WHICH MAY SEE SHOWERY WEATHER DUE TO THE
CORE OF THE UPR TROUGH AND THEN ONE OR MORE UPSTREAM FEATURES
DESCENDING FROM WRN CANADA... AND NRN AREAS OF THE PAC NW WHICH
WILL BE ON THE SRN PERIPHERY OF MOIST FLOW STREAMING INTO WRN
CANADA.  BELOW NORMAL TEMPS WILL PROGRESS FROM THE PLAINS INTO THE
EAST AND THEN MODERATE WHILE WARM TEMPS OVER THE WEST SHOULD
EXTEND EWD INTO PORTIONS OF THE PLAINS.  IN BOTH CASES ANOMALIES
MAY REACH AT LEAST 10F FROM NORMAL AT SOME LOCATIONS.

RAUSCH