ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 140 PM EST WED NOV 19 2014 VALID 12Z SUN NOV 23 2014 - 12Z THU NOV 27 2014 THIS ALASKA MEDIUM RANGE FORECAST PERIOD WILL SPELL A COLD AND DRY PERIOD OVER THE INTERIOR---WITH A GRADUAL SEEPAGE OF A MODIFIED ARCTIC AIRMASS TO THE SOUTHERN COASTAL FRINGES AND SHELTERED RIVER VALLEYS. THE TREND IS FOR A DRYING OUT PERIOD FROM WEST TO EAST---RELATIVELY SPEAKING. THE PANHANDLE REMAINS IN A FAVORABLE AREA FOR MID-LEVEL CLOUDINESS AND OCCASIONAL SHOWERS/RAIN IN THE DEFORMATION PRECIPITATION SHIELDS MOVING DOWNSTREAM---AND TO THEIR SOUTH IN THE STEERING CURRENTS OF THE PACIFIC JET (THROUGH DAY 6). THERE WAS NO MAJOR SHIFT IN FORECAST PHILOSOPHY WITH THE 19/00Z CYCLE. THE ECENS AND GEFS WERE BOTH REASONABLE PIECES OF GUIDANCE UNTIL 25/12Z---WHEN THEY DIVERGE ALONG THE SOUTHERN PANHANDLE...SOUTHWEST BC AND THE WASHINGTON/OREGON COAST. THE DIFFERENCES ARE SUBTLE---CONSIDERING THE PACIFIC JET STREAM AND MID-LATITUDE 'POLAR' FRONT HAS SPREAD OUT OVER A LARGE PORTION OF THE NORTH CENTRAL AND NORTHEAST PACIFIC...INCLUDING THE PACIFIC NORTHWEST COAST OF THE MAINLAND. THE DIFFERENCES ARE PRIMARILY A FUNCTION OF DEPTH...WITH A NOTABLY MID-LEVEL SHORTWAVE EJECTING EASTWARD FROM BRISTOL BAY/EASTERN ALEUTIANS---ACROSS THE NORTHERN GULF OF ALASKA. THIS SHORTWAVE MIGRATES---IN WHOLE OR PART---INTO AN UPPER-LEVEL RIDGE AXIS DRAPED OVER THE MOUNTAINS OF WESTERN AND NORTHWESTERN CANADA/NORTHEAST ALASKA. THE UNDERCUTTING MOISTURE AND ENERGY WILL EVENTUALLY MAKE A 'BEE-LINE' FOR SOUTHERN ALBERTA AND NORTHWEST MONTANA BY DAY 6-7...AND ALLOW A LOBE OF ARCTIC AIR TO SAG SOUTHWESTWARD ACROSS THE INTERIOR OF ALASKA---AND SPREAD NORTHEAST-TO-SOUTHWEST OVER MUCH OF THE STATE. VOJTESAK