EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1200 PM EDT SUN JUL 03 2016 VALID 12Z WED JUL 06 2016 - 12Z SUN JUL 10 2016 ...GUIDANCE/UNCERTAINTY ASSESSMENT... TO COMMENCE THE MEDIUM RANGE PERIOD...A HIGH LATITUDE BLOCK WILL REMAIN AN ISSUE TO CONTEND WITH AS A DOMINANT RIDGE HOLDS STRONG SOUTH OF THE NORTH POLE. THIS BLOCKING PATTERN SHOULD BE COMPLICATED AT TIMES AS IT CONTAINS BOTH A REX AND OMEGA DURING THE FORECAST. IN SPITE OF THESE COMPLEXITIES...THE GENERAL PATTERN ACROSS THE U.S. IS RESOLVABLE...ALBEIT WITH SPATIAL-TEMPORAL DIFFERENCES. TO START WITH...MODELS ARE IN AGREEMENT WITH A LONGWAVE/POSITIVELY-TILTED TROUGH ANCHORING THE PACIFIC NORTHWEST WHILE BROAD/LOW-AMPLITUDE WESTERLY FLOW ENCOMPASSES POINTS EASTWARD. THE KEY FEATURE EJECTING EASTWARD FROM THE UPPER INTERMOUNTAIN WEST EXHIBITS SOME MODEL VARIABILITY DURING THE MIDDLE/LATTER PART OF NEXT WEEK. OF NOTE...THE 00Z ECMWF/UKMET/ECMWF ENSEMBLE MEAN ARE DECIDEDLY WEAKER AND MORE PROGRESSIVE RELATIVE TO THE MORE DEVELOPED 06Z/00Z GFS AND 00Z CMC AS WELL AS THEIR RESPECTIVE MEANS. GIVEN THESE SOLUTIONS WERE MORE DEVELOPED RELATIVE TO VERIFICATION WITH THE ONGOING EVENT ACROSS THE MS RIVER VALLEY...PLAN ON STAYING MORE CONSERVATIVE HERE AS WELL LEANING IN THE DIRECTION OF THE 00Z ECMWF/UKMET. AS THIS PERTURBATION TRANSLATES EASTWARD...THE 00Z UKMET BECOMES TOO STRONG WITH SURFACE PRESSURES LOWERING TO 995-MB OVER THE UPPER GREAT LAKES BY THURSDAY MORNING. EVENTUALLY AN IMPRESSIVE UPPER LOW BEGINS TO DESCEND FROM THE NORTHEASTERN PACIFIC TOWARD WESTERN BRITISH COLUMBIA BY THE END OF THE WORK WEEK. THIS IS WELL AGREED UPON BY ALL DETERMINISTIC/ENSEMBLE SOLUTIONS WHICH WILL HELP BUILD HEIGHTS DOWNSTREAM OVER THE INTERMOUNTAIN WEST/ROCKY MOUNTAIN REGION. THE MORE DIFFICULT ASPECT OF THE FORECAST WILL BE RESOLVING THE SYNOPTIC PATTERN EAST OF THE GREAT PLAINS. ENSEMBLE SYSTEMS DIFFER FROM ONE ANOTHER WITH MANY SOLUTIONS FAVORING WEAK SOUTHEASTERLY FLOW ALOFT WITH RIDGING ACROSS THE SOUTHWESTERN ATLANTIC. IN THIS GROUP ARE THE 06Z/00Z GEFS AS WELL AS THE 00Z CMC/NAEFS ENSEMBLE MEANS. MEANWHILE...THE PAST FOUR CYCLES OF THE ECMWF ENSEMBLE MEAN FAVOR A BROAD UPPER TROUGH OVER THE NORTHEASTERN U.S. FOR NEXT WEEKEND. GIVEN THE OVERALL CONSISTENCY IN THIS SOLUTION COUPLED WITH STRONGER VERIFICATION SCORES IN RECENT MONTHS...GAVE MORE CREDIT TO THE 00Z ECMWF ENSEMBLE MEAN IN THE MODEL DURING THE DAY 5-7 PERIOD. STILL PLACED 20 PERCENT OF THE 00Z NAEFS ENSEMBLE MEAN INTO THE MIX DURING THAT FORECAST TIME SPAN GIVEN THE SPREAD IN THE SOLUTION ENVELOPE. ...WEATHER PATTERN THREATS/HIGHLIGHTS... THE PATTERN AS A WHOLE WILL FAVOR AT OR ABOVE NORMAL TEMPERATURES OVER A VAST MAJORITY OF THE COUNTRY. THE EXCEPTION TO THIS RULE WILL REMAIN ALONG THE WEST COAST GIVEN THE PERSISTENT UPPER TROUGH AFFECTING THE REGION. THIS FAVORS BELOW NORMAL READINGS EACH DAY WITH ANOMALIES IN THE 5 TO 10 DEGREE RANGE...PARTICULARLY CLOSER TO THE COAST WHERE COOL/MARITIME AIR WILL LEAD TO LOCAL SEA BREEZE EFFECTS. OTHERWISE...HOT CONDITIONS SHOULD REMAIN OVER THE SOUTHERN PLAINS...PARTICULARLY TX WHERE HIGHS WILL REMAIN IN THE LOWER 100S EACH DAYS. LOOKING TO PRECIPITATION...THE PREDICTABILITY FOR HEAVY RAINFALL IS NOT EXPECTED TO BE GREAT GIVEN THE MESOSCALE NATURE OF MANY OF THESE COMPLEXES. THE PRIMARY DRIVER EARLY IN THE PERIOD WILL BE WITH THAT SHORTWAVE EJECTING ACROSS THE NORTHERN HIGH PLAINS TOWARD THE UPPER GREAT LAKES. A COMPLEX OF CONVECTION SHOULD SLIDE EASTWARD WITH THIS SYSTEM WHILE THE WARM SECTOR SHOULD BE PREVALENT WITH SCATTERED THUNDERSTORMS AS THE THROUGH ADVANCES TOWARD THE EAST. RUBIN-OSTER