EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 133 AM EDT SAT AUG 09 2014 VALID 12Z TUE AUG 12 2014 - 12Z SAT AUG 16 2014 ...PREFERENCES... MANUAL PROGS USED AN OPERATIONAL MODEL/ENSEMBLE MEAN CONSENSUS THROUGH DAY 4 WED 13 AUG BUT REMOVED THE OPERATIONAL 12Z ECMWF AND 18Z GFS FROM THE BLEND AFTER WED DUE TO THEIR LOWER CONFIDENCE WRN-CNTRL NOAM SOLNS. THIS LEAD TO A BLEND OF THE 12Z ECMWF MEAN AND 18Z GEFS/12Z NAEFS MEANS FOR DAYS 5-7 THU-SAT 14-16 AUG. ...GUIDANCE EVALUATION... WITHIN THE CONSENSUS EXPECTATION OF A MEAN PATTERN CONSISTING OF A BERING SEA-ALEUTIANS UPR LOW AND NRN PAC TROUGH/INTERIOR WRN NOAM RIDGE/ERN NOAM TROUGH... THE MOST TROUBLESOME PART OF THE FCST CONTINUES TO INVOLVE THE HANDLING OF ENERGY APPROACHING THE WEST COAST AROUND NEXT TUE LEADING TO WIDENING MODEL/ENSEMBLE SPREAD FOR DETAILS OF FLOW ALOFT FROM THE WEST COAST WED-SAT. MODEL/ENSEMBLE SOLNS CONTINUE TO SHOW AN INCREASE IN SPREAD OVER THE ERN PAC/WRN NOAM AROUND 4-5 TUE-WED. THE 00Z 08 AUG ECMWF RUN OF A CLOSED LOW LINGERING NEAR THE CA/NV BORDER 12Z SAT WAS CONTRASTED BY THE 12Z 08 AUG RUN MOVING THE CLOSED LOW FURTHER NORTHEAST ABOUT 600 NM TO CENTRAL MT. THE 12Z ECMWF ENSEMBLE COVERED THESE OPTIONS AND EVERYTHING IN BETWEEN...WITH THE MEAN SOLUTION A BROAD POSITIVELY TILTED TROUGH. THE MEAN SOLUTION WAS PREFERRED UNTIL BETTER MODEL TO MODEL AND RUN TO RUN DIFFERENCES BECOME RESOLVED. ALSO...THERE WAS BETTER AGREEMENT AMONG THE MEANS THAN AMONG THE OPERATIONAL RUNS. THE 18Z-00Z GFS HAVE DIFFICULTY IN HANDLING A 700 MB TROUGH RIDING ACROSS BRITISH COLUMBIA INTO SOUTH CENTRAL CANADA AD THE NORTHERN PLAINS...WITH ANOMALOUS CLOSED LOWS SHOWING UP IN THE NORTHERN PLAINS TO UPPER MS VALLEY. GIVEN MARKED RUN TO RUN DIFFERENCES IN THE GFS AND LACK OF SUPPORT FROM THE GEFS MEAN..CONFIDENCE IS LOW IN THE GFS FOR THE PLAINS TO UPPER MS VALLEY THU 14 AUG TO SAT 16 AUG. ERN CONUS EVOLUTION IS SHOWING BETTER CLUSTERING...WITH MODEL/ENSEMBLE GUIDANCE SHOWING A PRENT CIRCULATION CROSSING THE LAKES INTO SOUTHEAST CANADA WHILE A NEW LOW FORMS NEAR THE MID ATLANTIC COAST AND MOVES UP THE COAST TOWARDS LONG ISLAND AND NEW ENGLAND. GOOD OVERLAP AMONG THE OPERATIONAL GFS/ECMWF AND THEIR RESPECTIVE MEANS LEAD TO A CONSENSUS APPROACH BEING USED...AND HIGH PROBABILITY OF PRECIPITATION VALUES IN THE REGION DAY 5/THU 14 AUG. ...SENSIBLE WEATHER HIGHLIGHTS... OVER THE WEST... A COMPACT UPR LOW EJECTING NEWD FROM THE NRN CA COAST SHOULD SUPPORT AN EPISODE OF ORGANIZED CONVECTION DURING THE FIRST HALF OF THE WEEK. THERE IS STILL SOME TRACK/TIMING UNCERTAINTY DUE TO ISSUES WITH APPROACHING UPSTREAM FLOW. EXPECT THE MOST PRONOUNCED TEMP ANOMALIES TO BE OVER THE INTERIOR NORTHWEST EXTENDING INTO WRN MONTANA WITH HIGHS SEVERAL DEGREES ABOVE NORMAL. CURRENTLY EXPECT BEST POTENTIAL FOR RNFL DURING THE MEDR PERIOD TO BE OVER THE SOUTHEAST WITH DEEP MSTR AND FRONTAL LIFT... AND OVER THE NORTHEAST IN ASSOC WITH STRONGEST DYNAMICS AND A PERIOD OF ONSHORE FLOW. FARTHER WWD MID LVL ENERGY REACHING THE PLAINS AND A COLD FRONT CROSSING THE NORTHERN PLAINS AND UPPER MS VALLEY WILL LIKELY SUPPORT CONVECTION. EXPECT MOSTLY BELOW NORMAL TEMPS FROM THE GREAT LAKES ACROSS THE NORTHEAST TO THE OH VALLEY/MID MS VALLEY/TN VALLEY/CENTRAL APPALACHIANS AND MID ATLANTIC STATES. THERE WILL BE MULTIPLE POCKETS OF MINUS 5-10F HIGH TEMPERATURE ANOMALIES. PETERSEN