EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1216 PM EDT THU JUL 17 2014 VALID 12Z SUN JUL 20 2014 - 12Z THU JUL 24 2014 ...OVERVIEW... AN ELONGATED UPPER TROUGH WILL GRADUALLY LIFT NORTHEASTWARD OUT THE EASTERN U.S. EARLY NEXT WEEK. UPSTREAM...THE FLOW WILL BECOME QUITE AMPLIFIED ACROSS THE WESTERN HALF OF THE NATION AS A CLOSED UPPER LOW BARRELS SOUTHWARD ALONG THE BRITISH COLUMBIA COAST INTO AN UPPER RIDGE ANCHORING ITSELF OVER THE FOUR CORNERS STATES. ENERGY SQUEEZING AROUND THE TOP OF THE BUILDING RIDGE HAS A CHANCE OF AMPLIFYING WHILE CROSSING INTO THE UPPER GREAT LAKES/MIDWEST TOWARDS THE MIDDLE OF NEXT WEEK. ...MODEL DIFFERENCES/PREFERENCES... MODELS WERE IN VERY GOOD AGREEMENT WITH THE MEAN FLOW PATTERN OVER THE CONUS THROUGH THE MEDIUM RANGE PERIOD...BUT DO SHOW SOME VARIATIONS WITH THE SMALLER SCALE DETAILS. EARLY IN THE PERIOD...THE FORECAST WAS BASED LARGELY OFF THE ECMWF...WHICH HAS BEEN MORE CONSISTENT THAN THE GENERALLY FASTER GFS WITH HOLDING HEIGHT FALLS BACK ACROSS THE TENNESSEE VALLEY/SOUTHERN TO CENTRAL APPALACHIANS SUNDAY INTO MONDAY. FOR THE MIDDLE TO LATER HALF OF THE PERIOD...THE FORECAST WAS HEAVILY WEIGHTED TOWARDS THE ECMWF ENSEMBLE MEAN. DETERMINISTIC GUIDANCE IS STILL SHOWING SOME RUN TO RUN DIFFERENCES WITH THE EXACT EVOLUTION OF THE CLOSED LOW DIVING DOWN THE BRITISH COLUMBIA COAST...AND THE ECMWF ENSEMBLE MEAN APPEARS TO OFFER A GOOD MIDDLE OF THE ROAD SOLUTION...WITHOUT OVERLY DAMPENING THE FEATURE LIKE THE 00Z GEFS MEAN. ALSO...THE ECMWF/ECMWF ENSEMBLE MEAN HAVE BEEN PERSISTENT WITH AMPLIFYING ENERGY ROUNDING THE UPPER RIDGE IN THE FOUR CORNERS WHILE IT CROSSES THE UPPER MIDWEST TOWARDS THE MIDDLE OF NEXT WEEK...A FEATURE IN WHICH ONLY SOME OF THE LATEST RUNS OF THE GFS HAS CAUGHT ONTO. ...SENSIBLE WEATHER HIGHLIGHTS... CONDITIONS WILL REMAIN WET AND STORMY BENEATH THE ELONGATED TROUGH LINGERING OVER THE EASTERN U.S. THIS WEEKEND AND INTO EARLY NEXT WEEK. PORTIONS OF THE GULF COAST STATES AND SOUTHEAST COULD SEE ESPECIALLY HEAVY RAINS...WHERE COPIOUS AMOUNTS OF MOISTURE WILL BE FEEDING INTO DEVELOPING PRECIPITATION. HEAVY RAINS AND CONVECTION WILL ALSO BE POSSIBLE ACROSS THE UPPER MIDWEST AS ENERGY AMPLIFIES ALOFT AND THE RESULTING SURFACE COLD FRONT CROSS THE REGION. IN TERMS OF TEMPERATURES ACROSS THE CONUS...ABOVE NORMAL CONDITIONS ARE EXPECTED BENEATH THE UPPER RIDGE ANCHORING ITSELF OVER THE FOUR CORNERS REGION WHILE HEIGHT FALLS FROM THE UPPER LOW BARRELING DOWN THE BRITISH COLUMBIA COAST SHOULD BRING BELOW NORMAL TEMPERATURES INTO THE PACIFIC NORTHWEST/WESTERN U.S.. GERHARDT