ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 220 PM EST MON NOV 09 2015 VALID 12Z FRI NOV 13 2015 - 12Z TUE NOV 17 2015 ALASKA'S MEDIUM RANGE WEATHER WILL BE DOMINATED BY A MODIFIED-ARCTIC AIRMASS --- AND AN UPPER-LEVEL FLOW PATTERN THAT ALLOWS THE FETCH OF AIR TO BE READILY TRANSPORTED FROM FAR NORTHEAST SIBERIA --- TO THE BERING SEA AND GULF OF ALASKA. THE CHALLENGE IN THE MEDIUM RANGE PERIOD WILL BE TO DETERMINE THE LEADING EDGES OF THESE AIRMASS AND THEIR IMPACTS ON THE FORECAST AREA --- WITH RESPECT TO APPRECIABLE SENSIBLE WEATHER CHANGES. THE 9/00Z GFS/ECMWF AND THEIR ENSEMBLE MEANS WERE IN VERY GOOD AGREEMENT WITH AN INTENSE DAY 4 SURFACE CYCLONE THAT SETTLES IN THE FAR NORTH CENTRAL GULF OF ALASKA AND CREATES A BROAD GYRE OF CYCLONIC LOW-LEVEL FLOW THAT TAKES IN ARCTIC AIR FROM THE NORTH AND NORTHWEST... THEN MODIFIES IT --- AND SPREADS IT DOWNSTREAM INTO THE WEST COAST OF NORTH AMERICA. ALOFT...THERE WAS NOT TOO MUCH DIFFERENCE BETWEEN THESE TWO SOLUTIONS THROUGH THE END OF THE WORK WEEK... AND A QUICK LOOK AT THE 9/12Z GFS/ECMWF SEEM TO HAVE A GOOD HANDLE ON THE UPPER-LEVEL SEQUENCING OF DISTURBANCE ROTATION FROM THE POLE (IE NORTH COAST OF NORTH SIBERIA) TO THE BERING SEA AND INTO THE BROAD LOW-LEVEL GYRE IN THE GULF. A BLEND OF THE ECENS/GEFS APPEARS TO MAINTAIN THIS COMPLEX POLAR FLOW QUITE WELL. VOJTESAK