EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 249 AM EDT TUE JUL 12 2016 VALID 12Z FRI JUL 15 2016 - 12Z TUE JUL 19 2016 ...PATTERN OVERVIEW/GUIDANCE EVALUATION/PREFERENCES... TO BEGIN THE FORECAST PERIOD...A LONGWAVE TROUGH WILL BE POSITIONED OVER THE NORTHEASTERN PART OF NORTH AMERICA WITH WEAK TO MODEST PERTURBATIONS MIGRATING FROM THE MO VALLEY TOWARD THE CENTRAL APPALACHIANS. BY THE WEEKEND...THE STRONGER HEIGHT FALLS SHOULD CONTINUE LIFTING INTO EASTERN CANADA WITH RESIDUAL SOUTHWESTERLY ALOFT SETTLING OVER THE NORTHEASTERN U.S. OVER THE WESTERN STATES...A COMPACT CLOSED LOW WILL BE UNDERCUTTING A SPRAWLING RIDGE ACROSS NORTHWESTERN CANADA. THIS DISTURBANCE SHOULD GENERALLY BE IN THE VICINITY OF THE WA/BC BORDER ON FRIDAY MORNING WITH AGREEMENT NOTED BETWEEN THE 18Z GFS AND 12Z ECMWF/CMC. CHOSE TO NOT INCLUDE THE 12Z GFS AS IT WAS WELL OFF TO THE NORTHWEST WHICH HAD MINIMAL ENSEMBLE SUPPORT. MANY OF THE 00Z SOLUTIONS...CMC/UKMET...TRENDED QUICKER SO THERE IS STILL SOME ROOM FOR ADJUSTMENTS THE NEXT FEW MODEL CYCLES. THIS FEATURE SHOULD GRADUALLY SHEAR AS IT ENCOUNTERS BUILDING HEIGHTS ACROSS THE ROCKIES/HIGH PLAINS BY LATER IN THE WEEKEND. THERE IS STRONG SUPPORT FOR A MORE PRONOUNCED UPPER TROUGH TO SINK DOWN THE PACIFIC NORTHWEST COAST ON DAY 5/SUNDAY WITH HEIGHTS CONTINUING TO BUILD DOWNSTREAM OVER THE FOUR CORNERS REGION AND ADJACENT GREAT PLAINS. WHILE THE ORIENTATION/DEPTH OF THIS TROUGH VARIES AMONG THE GUIDANCE...THE IDEA OF ITS PRESENCE IS WELL SUPPORTED. WHAT SEEMS TO BE A MORE CONTENTIOUS AREA ON THE MAP IS WITH THE AMPLIFICATION IN THE NORTHERN STREAM ACROSS EASTERN CANADA. ENSEMBLE SPAGHETTI PLOTS SHOW QUITE A BIT OF SCATTER WITH RUN-TO-RUN CONTINUITY ON THE POOR SIDE. FOR INSTANCE...THE 00Z GFS JUST TRENDED ABOUT 12 TO 18 HOURS SLOWER WITH THIS TROUGH JUST ON DAY 5. WITH THAT SAID...THE 12Z ECMWF AND ITS INTENSE CIRCULATION WAS DISMISSED BY DAY 5.5. REGARDING THE PREFERENCE...WENT WITH A 3-WAY COMBINATION OF THE 18Z GFS/12Z ECMWF/CMC WITH MORE EMPHASIS ON THE GFS/ECMWF THROUGH DAY 4. THEREAFTER...STARTED INCORPORATING INCREASING USE OF THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS WHILE MAINTAINING A HEALTHY AMOUNT OF THE 18Z GFS...AT LEAST FOR DAY 5. EVENTUALLY WENT TO ALL ENSEMBLES BY DAY 7/JULY 19 WITH SLIGHTLY MORE WEIGHTING TOWARD THE 18Z GEFS MEAN. ...WEATHER HIGHLIGHTS/THREATS... FORECAST TEMPERATURE ANOMALIES WILL NOT BE TERRIBLY SIGNIFICANT THROUGHOUT THE MEDIUM RANGE. SPOTS OF THE COUNTRY WHICH CAN EXPECT BELOW NORMAL READINGS WILL BE OVER THE NORTHERN PLAINS/UPPER MIDWEST DOWN INTO THE MIDDLE MS VALLEY RESIDING GENERALLY IN THE POST-COLD FRONTAL ENVIRONMENT. ADDITIONALLY...THE DAILY THREAT FOR PRECIPITATION SHOULD ALSO HELP KEEP READINGS DOWN A BIT GIVEN INCREASING CLOUD COVER. ELSEWHERE...EXPECT HIGHS ABOUT 5 TO POSSIBLY 10 DEGREES BELOW NORMAL OVER THE PACIFIC NORTHWEST LATE IN THE PERIOD AS THE UPPER TROUGH BEGINS TO TAKE SHAPE. MEANWHILE...UNDER THE RIDGE FROM THE DESERT SOUTHWEST TO THE SOUTHERN PLAINS...EXPECT HOT CONDITIONS TO PREVAIL WITH DESERT LOCALES REACHING THE 110 TO 115 DEGREE RANGE EACH DAY. MODERATE TO HEAVY RAINFALL IS LIKELY ANYWHERE FROM THE NORTHERN TIER STATES SOUTHEASTWARD THROUGH THE OZARKS AND INTO THE MID-ATLANTIC/CAROLINAS. THIS WILL FOCUS ALONG THE CONSTANTLY MEANDERING FRONTAL ZONE WHICH SHOULD OFTEN RE-POSITION BASED ON CONVECTIVE PROCESSES/TRENDS. ADDITIONAL CONVECTION IS POSSIBLE WITHIN THE WARM SECTOR ITSELF...PARTICULARLY ALONG THE CENTRAL/EASTERN GULF COAST WHERE SEA BREEZE ACTIVITY MAY LEAD TO LOCAL MESOSCALE ENHANCEMENTS. RUBIN-OSTER