ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 225 PM EST TUE JAN 16 2018 VALID 12Z SAT JAN 20 2018 - 12Z WED JAN 24 2018 FOR THE MEDIUM RANGE FORECAST PERIOD...A RIDGE WILL CENTER ITSELF OVER NORTHERN ALASKA EXTENDING FROM ASIA...WITH SYSTEMS UNDERCUTTING THE RIDGE INTO THE GULF OF ALASKA THROUGH THE FORECAST PERIOD. A LARGE OCCLUSION WILL APPROACH WESTERN ALASKA/ALEUTIAN ISLANDS BY SATURDAY AND INTO SUNDAY...AND MOVE INTO THE GULF OF ALASKA BY DAY 6/MONDAY. AT FIRST...THE 06Z GFS AND 00Z ECMWF DIFFERED ON THE SOLUTION OF THIS PARTICULAR SURFACE LOW...WITH THE 06Z GFS SHOWING THE SURFACE LOW ABSORBING INTO THE TROUGH SET UP ALONG THE SOUTHERN ALASKAN COAST. THE 00Z ECMWF SHOWED THE LOW MOVING FARTHER SOUTH INTO THE NORTH PACIFIC. THE 12Z GFS SHOWED A SIMILAR PATH TO THIS LOW. THIS SYSTEM WILL APPROACH THE COAST BY DAY 8/WEDNESDAY. GIVEN THAT THE RIDGE OVER ALASKA WILL STAY IN PLACE OVER THE MEDIUM RANGE PERIOD, THE SOUTHERN TRACK SEEMS MORE LIKELY OF A SOLUTION. OTHERWISE...MOST OF THE GUIDANCE SEEMED IN FAIR AGREEMENT THUS TOOK A BLEND OF THE 00Z ECMWF/12Z GFS AND THE 06Z GEFS MEAN/00Z ECENS WITH MORE WEIGHT ON THE ENSEMBLE MEANS BY THE END OF THE PERIOD. PRECIPITATION WILL BEGIN TO STEADILY INCREASE BY MONDAY AS AN INCREASE IN MOISTURE FROM THE GULF OF ALASKA MOVES NORTHWARD INTO THE SOUTHERN ALASKAN COAST. THIS INCREASE IN CHANCE OF PRECIPITATION WILL PERSIST THROUGH WEDNESDAY AND IS EXPECTED TO BE CONFINED TO THE COAST. TEMPERATURES ARE EXPECTED TO BE NEAR AVERAGE. REINHART