EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1139 AM EDT SUN JUN 16 2013

VALID 12Z WED JUN 19 2013 - 12Z SUN JUN 23 2013

...OVERVIEW AND PREFERENCES...

MOST OF THE CONUS SHOULD SEE GRADUALLY RISING HGTS OVER THE COURSE
OF THE PERIOD AS A NWRN CONUS CLOSED LOW DRIFTS NEWD INTO SRN
CANADA... A RIDGE OVER THE PLAINS BUILDS INTO THE MS VLY... AND
ERN CONUS TROUGHING RELAXES.  THERE IS ALSO DECENT AGREEMENT THAT
THE FOCUS OF NWRN NOAM RIDGING WILL TRANSITION FROM NRN ALASKA TO
WRN CANADA WHILE HGT FALLS TRAVERSING THE NRN PACIFIC COULD START
COMING INTO THE PICTURE OFFSHORE THE NWRN COAST BY THE END OF NEXT
WEEKEND.  WITH FAVORABLE TRENDS IN THE 06Z GEFS MEAN RELATIVE TO
THE 00Z VERSION... A BLEND OF THE 06Z GEFS/00Z ECMWF ENSEMBLE
MEANS PROVIDES A REASONABLE STARTING POINT TO EMPHASIZE THE MOST
AGREEABLE ASPECTS OF LATEST GUIDANCE ACROSS THE CONUS AND
VICINITY.  THE INITIAL BLEND IS LOCALLY ADJUSTED WHERE A BETTER
DEFINED OPERATIONAL CONSENSUS EXISTS AND IN PARTICULAR WITH THE
NWRN CONUS CLOSED LOW FOR WHICH THE GEFS MEAN MAY BECOME A LITTLE
FAST FRI ONWARD. 


...GUIDANCE EVALUATION...

MEDIUM RANGE GUIDANCE CONTINUES TO SHOW BETTER THAN AVG AGREEMENT
WITH THE FAIRLY DEEP CLOSED LOW FCST TO CROSS THE EXTREME
NORTHWEST AND CONTINUE INTO SRN CANADA.  THE MAIN COMPLICATING
FACTOR IN THE FCST OF THIS FEATURE WILL LIKELY BE IN THE FRI-SUN
TIME FRAME AS DIFFS STILL EXIST IN EXACTLY HOW THE WRN CANADA
RIDGE WILL EVOLVE.  THE 00Z ECMWF LEANS A BIT TO THE SLOW SIDE OF
THE SPREAD WITH THE CLOSED LOW BY NEXT WEEKEND AS THE RIDGE TO THE
N BUILDS FARTHER EWD THAN MOST OTHER MODELS/ENSEMBLES... SO AT THE
VERY LEAST WOULD LEAN SOMEWHAT AWAY FROM THAT ASPECT OF THE 00Z
ECMWF.  UPSTREAM THE 00Z CMC/CMC MEAN ARE FASTEST TO BRING PACIFIC
HGT FALLS TOWARD THE WEST COAST LATE IN THE PERIOD. 
TELECONNECTIONS RELATIVE TO THE WRN CANADA RIDGING FAVOR SOME
DEGREE OF HGT FALLS REACHING THE ERN PAC/WEST COAST BUT SUCH
FAVORED PATTERNS USUALLY TAKE A LITTLE TIME TO EVOLVE SO A SOLN
SOMEWHERE BETWEEN THE GEFS/ECMWF MEANS AND SLIGHTLY STRONGER
GFS/ECMWF RUNS SEEM MORE REASONABLE AT THIS TIME.

FARTHER EWD... THE FOCUS EARLY IN THE PERIOD WILL BE ON SMALLER
SCALE SHRTWV DETAILS WITHIN THE MEAN TROUGH ALOFT.  THE 00Z/06Z
GFS ARE SLOWER THAN MOST OTHER GUIDANCE WITH A WAVE WHICH THE GFS
TRACKS SLOWLY OFF THE NC COAST.  GFS RUNS MAY ALSO BE A BIT ON THE
STG SIDE WITH A MID LVL IMPULSE TRACKING FROM THE PLAINS INTO MS
VLY.  BY MID-LATE PERIOD THE 00Z GFS/CMC TREND SIGNIFICANTLY OUT
OF PHASE RELATIVE TO CONSENSUS WITH NRN-ERN CANADA FLOW.  THE
RESULTING RIDGE WHICH THOSE SOLNS BRING INTO THE GRTLKS/NORTHEAST
SAT-SUN IS ON THE EXTREME EDGE OF THE GEFS/ECMWF ENSEMBLE SPREAD. 
HAVING A SHRTWV RIDGE PASS THROUGH THE ERN CANADA/NERN CONUS MEAN
TROUGH IS NOT OUT OF THE QUESTION.  HOWEVER WITH TELECONNECTIONS
RELATIVE TO THE WRN CANADA RIDGE SUPPORTING FLAT TO CYCLONIC FLOW
DOWNSTREAM... WOULD GREATLY PREFER THE 06Z GEFS/00Z ECMWF MEANS. 
THE 06Z GFS HAS ADJUSTED FAIRLY CLOSE TO THIS PREFERRED SOLN.  THE
00Z ECMWF FITS PREFS IN PRINCIPLE BUT COULD BE A LITTLE OVERDONE
SFC/ALOFT OVER THE GRTLKS/NEW ENG BY DAY 7 SUN.


...SENSIBLE WEATHER HIGHLIGHTS...

CLOSED LOW ALOFT CROSSING THE NORTHWEST WILL BRING UNSETTLED
WEATHER FROM THE PAC NW INTO THE NRN ROCKIES MID-LATE WEEK... WITH
A DRYING TREND EXPECTED BY NEXT WEEKEND.  EXPECT UNSEASONABLY LOW
MAX TEMPS OVER THE NORTHWEST/NRN ROCKIES AND TO A LESSER EXTENT
NRN HIGH PLAINS WED INTO FRI.  AN ISOLATED RECORD COOL HIGH WOULD
NOT BE OUT OF THE QUESTION ON WED-THU.  ALONG WITH THE DRYING
TREND OVER NRN AREAS LATE IN THE PERIOD... MOST OF THE WEST SHOULD
SEE TEMPS TRENDING ABOVE NORMAL AS HGTS ALOFT STEADILY RISE. 
MEANWHILE MSTR FROM THE NWRN SYSTEM SHOULD STREAM EWD ACROSS THE
NRN PLAINS AND EVENTUALLY INTO THE GRTLKS WITH SOME LOCALLY HVY
CONVECTION PSBL.  EXPECT DIURNALLY ENHANCED CONVECTION OVER THE
SOUTHEAST WITH A WEAKENING FRONTAL BNDRY HELPING TO FOCUS ACTIVITY
DURING THE FIRST HALF OF THE PERIOD.  ALSO CONVECTION MAY
ACCOMPANY THE TRAILING PART OF THE FRONT EXTENDING INTO THE PLAINS
WED INTO THU.  THE GREATEST ANOMALIES ON THE WARM SIDE SHOULD BE
OVER THE CNTRL HIGH PLAINS THU-FRI.  SOME OF THIS WARMTH SHOULD
SPREAD EWD INTO PARTS OF THE MS VLY/OH VLY BY LATE THIS WEEK INTO
THE WEEKEND.

RAUSCH