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Extended Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1523Z Mar 04, 2015)
 
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EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1023 AM EST WED MAR 04 2015

VALID 12Z SAT MAR 07 2015 - 12Z WED MAR 11 2015

...OVERVIEW...

EXPECT A GRADUAL FLATTENING OF NRN STREAM FLOW AS THE WEST
COAST/ERN PAC RIDGE ALOFT WEAKENS AND DRIFTS A LITTLE EWD... WHILE
A TROUGH SHOULD PERSIST FROM THE SRN ROCKIES/PLAINS INTO MEXICO. 
ENERGY ASSOC WITH AN UPR LOW NEAR INITIALLY NEAR 150W MAY TRY TO
APPROACH THE WEST COAST BY THE END OF THE PERIOD.  BY MID-LATE
PERIOD THE MOST PROMINENT DIFFS THAT ARISE INVOLVE THE PHASE OF
NRN CONUS/SRN CANADA FLOW ALONG WITH TIMING OF THE UPR SYSTEM OFF
THE WEST COAST.  ALSO EARLIER IN THE PERIOD THERE ARE ISSUES WITH
HOW A COMPACT UPR LOW EJECTS FROM THE WRN HALF OF THE US-MEXICO
BORDER.


...GUIDANCE EVALUATION AND PREFERENCES...

THE MOST SIGNIFICANT NRN STREAM DIFFS THAT ARISE IN THE GUIDANCE
MID-LATE PERIOD ORIGINATE FROM THE EXTREME NERN PAC SUN-MON AS
00Z-06Z GFS/GEFS MEAN RUNS DEVELOP GREATER TROUGH AMPLITUDE VERSUS
MOST OTHER SOLNS... LEADING TO CONSIDERABLY OUT OF PHASE PATTERNS
OVER WRN CANADA BY NEXT TUE-WED.  D+8 MEANS INDICATE TWO PROMINENT
HGT ANOMALIES... A POSITIVE CENTER TO THE S OF THE WRN ALEUTIANS
AND A NEGATIVE CENTER NEAR THE SRN TIP OF GREENLAND. 
TELECONNECTIONS RELATIVE TO THESE FEATURES SHOW FAIRLY FLAT CONUS
FLOW BUT SHOW A FAINT HINT OF WRN RIDGING AND ERN TROUGHING.  THE
NON-GFS CLUSTER OFFERS A BETTER FIT TO THIS FAVORED PATTERN.  EVEN
EARLIER IN THE PERIOD THE GFS/GEFS MEAN ARE SOMEWHAT OUT OF PHASE
AND DIFFER IN AMPLITUDE RELATIVE TO THE MAJORITY CLUSTER WITH
FEATURES ACROSS THE NRN TIER.  WITH THESE CONSIDERATIONS IN
MIND... PREFER AN UPDATED BLEND THAT INCORPORATES THE MORE LIKELY
CLUSTER OF LATEST GUIDANCE ALONG WITH CONTINUITY.  THIS LEADS TO
STARTING WITH HALF WEIGHTING OF THE 00Z ECMWF MEAN ALONG WITH
REMAINING INPUT FROM THE 00Z NAEFS MEAN/WPC CONTINUITY.

THE ONE QUESTION MARK PRESENT IN ABOVE FCST PREFERENCE IS TIMING
OF THE SYSTEM NEARING THE WEST COAST BY DAY 7 WED.  THE INITIAL
UPR LOW IS RATHER WELL SEPARATED FROM THE WESTERLIES INTO DAY 6
TUE WITH ACCELERATION OCCURRING AS UPSTREAM TROUGHING AMPLIFIES. 
IT WOULD NOT BE SURPRISING IF TIMING WERE TO BE A LITTLE SLOWER
THAN IN THE FAVORED BLEND BUT AT LEAST HGT FALLS NEAR THE WEST
COAST ARE LESS PRONOUNCED THAN FCST BY THE 00Z ECMWF/CMC RUNS.

GUIDANCE IS NEARLY SPLIT WITH EJECTION OF A COMPACT UPR LOW
INITIALLY ALONG THE WRN US-MEXICO BORDER... AS THE 00Z-06Z GFS AND
GEFS MEAN/00Z CMC BECOME CONSIDERABLY FASTER THAN THE 00Z
UKMET/ECMWF/ECMWF MEAN.  THE 00Z CMC MEAN SIDES WITH THE SLOWER
CLUSTER TO PROVIDE MODEST SUPPORT FOR THE MANUAL BLEND THAT
PRIMARILY REFLECTS THE SLOWER TIMING.


...SENSIBLE WEATHER HIGHLIGHTS...

THE DETAILS REMAIN UNCERTAIN BUT THERE IS STILL POTENTIAL FOR ONE
OR MORE PERIODS OF ENHANCED RNFL OVER THE GULF COAST/SOUTHEAST...
WITH THE POSSIBILITY THAT SOME OF THIS MSTR COULD EXTEND FARTHER
NWD DURING A PORTION OF THE PERIOD.  RELATIVE TO RECENT GFS/GEFS
MEAN RUNS THE CURRENT PREFS ALOFT WOULD SUGGEST SOMEWHAT MORE RNFL
OVER THE SOUTHEAST EARLY NEXT WEEK AND A MORE SUPPRESSED PCPN
SHIELD BY MIDWEEK.  ELSEWHERE PCPN SHOULD BE ON THE LGT SIDE...
WITH A LITTLE MSTR REACHING THE WEST COAST LATE IN THE PERIOD
AHEAD OF THE APPROACHING ERN PAC SYSTEM AND AT LEAST A COUPLE
AREAS OF MOSTLY LGT SNOW ACCOMPANYING A SERIES OF FRONTAL SYSTEMS
CROSSING UPR MIDWEST/GRTLKS/NEW ENGLAND.  ABOVE NORMAL TEMPS OVER
THE WEST AND INTO THE NRN PLAINS SHOULD SPREAD INTO THE CNTRL
PLAINS/MIDWEST BY NEXT WEEK.  SOME ANOMALIES REACHING PLUS 10-15F
ARE PSBL OVER NRN-CNTRL PARTS OF THE WEST MOST DAYS... AND UP TO
PLUS 15-20F IN THE NRN HALF OF THE PLAINS MON-WED.  ON THE OTHER
HAND HIGHS MAY BE UP TO 10-20F BELOW NORMAL OVER THE SRN
PLAINS/LWR MS VLY SAT-SUN BEFORE MODERATING.  BELOW NORMAL
READINGS OVER THE EAST SHOULD TREND TO NEAR OR SLIGHTLY ABOVE
NORMAL LATE IN THE PERIOD.

RAUSCH