ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 312 PM EDT WED AUG 19 2015 VALID 12Z SUN AUG 23 2015 - 12Z THU AUG 27 2015 THE 19/00Z ECENS/GEFS SOLUTIONS LOOKED VERY REASONABLE THROUGH DAY 5 (24/12Z) FOR THE ALASKA MEDIUM RANGE---WITH A PATTERN 'TRANSITION' FOR ALASKA (DAYS 6-8) STARTING IN THE FAR SOUTHWEST AND ATTEMPTING TO WORK EAST ACROSS THE SOUTHERN BERING AND WESTERN ALEUTIANS. WILL CONTINUE HOLDING A 'SLOT' FOR 'ATSANI' INVOF 40N AND THE DATELINE IN LINE WITH THE 19/00Z ECENS MEANS---WITH THE 19/00Z AND 19/06Z GEFS BEGINNING TO OUTPACE THE ECENS BY 24/12Z. THE PATTERN OVER THE NORTHEAST PACIFIC IS RATHER STABLE...WITH A PRONOUNCED DEEP-LAYERED RIDGE CENTERED INVOF 45N 150W FOR MUCH OF THE MEDIUM RANGE. THIS IN ITSELF...SHOULD ALLOW FOR A GENERAL WEST TO NORTHWEST FLOW PATTERN FOR THE MAINLAND (ALASKA) AND NW-TO-SE SHORTWAVE PROGRESSION FOR MUCH OF THE PERIOD. CONCERNING A PATTERN CHANGE... STILL NO 'PERFECT PROG' SOLUTION OUT THERE BEYOND DAY 5---AND THE ADJUSTMENTS SEEN AT DAY 4---FROM 24 HOURS AGO--- IN THE TROPICAL SW PAC WILL LIKELY CONTINUE WITH THE 19/12Z DETERMINISTIC SPREAD AT DAY 6 (VALID 25/12Z) BEING APPROXIMATELY 520NM. AT DAY 6...THE DETERMINISTIC 19/12Z CANADIAN BEING ON THE FAST/NORTHEAST SIDE OF THE ENVELOPE AND THE 19/12Z ECMWF ON THE SLOW/SOUTHWEST SIDE OF THE FORECAST ENVELOPE. THE 19/12Z GFS CLOSER TO THE CANADIAN VERSUS THE ECMWF. BY DAY 8 (VALID AT 27/12Z)... THE DIFFERENCE BETWEEN THE 19/12Z DETERMINISTIC ECMWF/GFS? --- A GRAND TOTAL OF 1200NM! THE ECMWF---SLOW AND GFS---FAST. VOJTESAK