EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 244 AM EDT SUN JUL 09 2017 VALID 12Z WED JUL 12 2017 - 12Z SUN JUL 16 2017 ...PATTERN OVERVIEW AND GUIDANCE EVALUATION/PREFERENCES... GUIDANCE CONTINUES TO SHOW THAT AN ELONGATED CONUS RIDGE AS OF MIDWEEK WILL CONSOLIDATE/REBUILD OVER THE WEST LATE IN THE WEEK AND PERSIST OVER THE REGION THROUGH THE WEEKEND. AS THIS OCCURS EXPECT NRN TIER U.S./SRN CANADA ENERGY TO RE-AMPLIFY THE ERN U.S. MEAN TROUGH. THERE IS POTENTIAL FOR UPSTREAM CANADIAN FLOW TO REINFORCE THE TROUGH LATE IN THE PERIOD BUT THIS IS LESS CERTAIN. AN UPR LOW MEANDERING TO THE S/SW OF THE ALASKA PANHANDLE MAY BEGIN TO DRIFT TOWARD THE BC COAST NEXT WEEKEND. DAYS 3-5 WED-FRI STARTED WITH AN OPERATIONAL BLEND CONSISTING OF THE 12Z ECMWF/12Z-18Z GFS/12Z UKMET. THE PRIMARY UNCERTAINTY IN THIS TIME FRAME CONTINUES TO BE AN AREA OF LOW PRESSURE MOST LIKELY TO TRACK FROM THE UPR MS VLY INTO SRN NEW ENGLAND/NRN MID ATLC, IN RESPONSE TO INITIAL NRN TIER/SRN CANADA ENERGY ALOFT. GFS RUNS SINCE 12Z (INCLUDING THE NEW 00Z VERSION) ARE STILL A BIT ON THE NRN SIDE OF THE ENVELOPE BUT MUCH CLOSER TO THE MORE STABLE ECMWF/UKMET SCENARIO THAN SOME RUNS WERE PREVIOUSLY. CMC RUNS CONTINUED TO REPRESENT A SUPPRESSED EXTREME UNTIL ARRIVAL OF THE NEW 00Z RUN THAT HAS FINALLY JOINED CONSENSUS. THE FAVORED BLEND YIELDED A REASONABLE INTERMEDIATE TRACK/DEPTH AT THE SFC WITH SOME MODEST DETAIL ADJUSTMENTS VS CONTINUITY PER LATEST TRENDS. INFLUENCE OF CONVECTIVE SYSTEMS TYPICALLY NOT WELL FCST BY GLOBAL MODELS IS A NOTABLE WILD CARD IN THE FCST. AS OPERATIONAL RUNS DIVERGE MORE SIGNIFICANTLY AFTER DAY 5 FRI THE FAVORED BLEND RAPIDLY INCREASED ENSEMBLE MEAN WEIGHT SO THAT DAY 7 CONSISTENT ENTIRELY OF THE 18Z GEFS AND 12Z NAEFS/ECMWF MEANS. BY THE LATTER HALF OF THE PERIOD INDIVIDUAL SOLNS BEGIN TO DIFFER ON THE DEGREE OF NERN PAC UPR LOW PROGRESSION AND/OR HOW MUCH SURROUNDING ENERGY MAY BEGIN TO EJECT INLAND. DIFFS HERE IMPACT THE AMPLITUDE/AXIS OF THE ERN TROUGH. IN THIS LONG TERM PATTERN OVER AT LEAST THE PAST 1-2 WEEKS, ALL MODEL SYSTEMS HAVE AT DIFFERENT TIMES OCCASIONALLY BEEN FAST TO BRING NERN PAC UPR LOW ENERGY INLAND. CURRENTLY THE GFS/GEFS HOLD ONTO A STRONGER WRN RIDGE/SLOWER UPSTREAM LOW WITH THE 12Z CMC MEAN A COMPROMISE WITH THE FLATTER ECMWF/ECMWF MEAN AND NOW 00Z CMC. GIVEN THESE CONSIDERATIONS THE FAVORED BLEND WENT ABOUT 2/3 TOWARD THE 18Z GEFS/12Z NAEFS MEANS VS THE ECMWF MEAN. WITH THIS SOLN THE ERN TROUGH IS DEEPER/SLOWER THAN THE ECMWF/ECMWF MEAN BUT NOT TO THE EXTENT OF OPERATIONAL GFS RUNS WHICH AT TIMES HAVE BEEN ON THE DEEPER SIDE OF THE SPREAD. ...WEATHER HIGHLIGHTS... A WAVY FRONTAL BOUNDARY PUSHING GRADUALLY SEWD FROM THE UPR MIDWEST/LWR GREAT LAKES TOWARD THE CAROLINAS WILL BE THE MOST PROMINENT FOCUS FOR CONVECTION DURING THE PERIOD. LOCATIONS WITHIN/BETWEEN THESE REGIONS AS WELL AS PARTS OF THE NORTHEAST WILL SEE POTENTIAL FOR ONE OR MORE EPISODES OF HEAVY RAINFALL. MONITOR SPC OUTLOOKS FOR UPDATED INFO REGARDING SEVERE THREATS. DEPENDING ON SPECIFICS OF FLOW ALOFT, UPSTREAM ENERGY COULD GENERATE AREAS OF SHWRS/TSTMS FROM THE NRN TIER SEWD BY NEXT WEEKEND BUT CONFIDENCE IN THIS PART OF THE FCST IS FAIRLY LOW. MEANWHILE EXPECT PERIODS OF DIURNALLY FAVORED CONVECTION OVER THE GULF COAST/FLORIDA/SOUTHEAST WITH SOME LOCALLY ENHANCED TOTALS. MONSOONAL ACTIVITY PRIMARILY OVER THE FOUR CORNERS STATES MAY BEGIN TO DRIFT INTO THE SOUTHWEST BY NEXT WEEKEND AS RIDGING ALOFT BECOMES ESTABLISHED OVER OR NEAR THE GREAT BASIN. WITH THE UPR RIDGE REBUILDING OVER THE WEST, EXPECT THE HEAT OVER THE NRN INTERIOR WEST/ROCKIES TO PERSIST/INTENSIFY AND SPREAD INTO THE NRN PLAINS WITH TIME. THERE SHOULD BE FAIRLY BROAD COVERAGE OF HIGHS 10-20F ABOVE NORMAL AND INCREASING POTENTIAL FOR SOME SCATTERED DAILY RECORD VALUES FOR MAX AND/OR WARM MIN READINGS BY NEXT WEEKEND. THE REMAINDER OF THE INTERIOR WEST WILL SEE ABOVE NORMAL TEMPS WITH SOMEWHAT LESS EXTREME ANOMALIES, THOUGH PARTS OF THE CNTRL VALLEY OF CA AND GREAT BASIN MAY STILL END UP 10F OR SO ABOVE NORMAL BY SAT-SUN. ESPECIALLY DURING THE FIRST HALF OF THE PERIOD THE WAVY FRONT OVER THE EAST MAY PROVIDE A SHARP CONTRAST BTWN VERY WARM TO HOT TEMPS TO THE S AND NEAR TO BELOW NORMAL TEMPS TO THE N. RAUSCH