ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 355 PM EDT SAT OCT 08 2016 VALID 12Z WED OCT 12 2016 - 12Z SUN OCT 16 2016 ...GUIDANCE AND UNCERTAINTY ASSESSMENT... THE LARGE-SCALE SYNOPTIC PATTERN WILL CONTINUE TO BE DOMINATED BY AN OMEGA BLOCK SET UP FROM THE POLAR REGION SOUTHWARD ACROSS MUCH OF MAINLAND AK INTO WESTERN CANADA. BEYOND WEDNESDAY...MODELS DO ERODE THE SOUTHERN EXTENT OF THIS MEAN RIDGE AS UPSTREAM HEIGHT FALLS TRAVERSE TOWARD BRITISH COLUMBIA. ULTIMATELY WHAT REMAINS OF THIS RIDGE WILL ANCHOR ITSELF OVER NORTHERN AK WHILE SLOWLY DRIFTING WESTWARD IN TIME. THE BREAK DOWN OF THE CORE OF THIS RIDGE AXIS WILL ALLOW THE PERSISTENT NEGATIVE ANOMALIES ACROSS THE BERING SEA/ALEUTIANS/NORTH-CENTRAL PACIFIC TO TRANSLATE EASTWARD. HOW THIS OCCURS IS VERY UNCERTAIN GIVEN THE NUMBER OF EMBEDDED SHORTWAVES TO CONSIDER. AS EXPECTED...ENSEMBLE SOLUTIONS HAVE TENDED TO LUMP THE PRIMARY AND TRIPLE POINT CYCLONES INTO ONE MAIN AREA OF LOW PRESSURE WHICH IS NOT DESIRABLE. THE OTHER AREA TO CONSIDER ON THE MAP IS ACROSS THE POLAR REGIONS OF CANADA. MODELS ADVERTISE A CORE OF LOWER HEIGHTS DROPPING DOWN THROUGH NORTHEASTERN AK WITH RECENT GFS SOLUTIONS MORE EMPHATIC IN DENTING THE EASTERN EXTENT OF THE UPPER HIGH. THE 00Z ECMWF AND PREVIOUS VERSIONS FORCE THE SHORTWAVE ENERGY TO STAY EAST OF NORTHERN AK FOR THE MOST PART. CONSIDERING THE PREFERRED SOLUTION HERE...THE OUTPUT WAS DRIVEN BY THE 00Z ECMWF AND 06Z GEFS/00Z ECMWF ENSEMBLE MEANS AFTER COORDINATION WITH AK REGION OFFICES. FOR DAY 4/WEDNESDAY...LEANED ON A COMBINATION OF THE 00Z ECMWF AND THE ABOVE ENSEMBLE MEANS WITH THE ECMWF UTILIZED TO GET MORE DETAIL WITH THE SURFACE CYCLONE EVOLUTIONS/STRUCTURES. FROM THERE ON...SPLIT THE DIFFERENCE BETWEEN THE 06Z GEFS/00Z ECMWF ENSEMBLE MEANS THROUGH NEXT WEEKEND. ...WEATHER HIGHLIGHTS/THREATS... THE PERSISTENCE OF UPPER RIDGING OVER MUCH OF MAINLAND AK WILL KEEP CONDITIONS DRY WITH ABOVE NORMAL TEMPERATURES. TO THE SOUTH...THE WETTEST AREA DURING THE FORECAST WILL REMAIN OVER THE ALEUTIANS GIVEN THE CONTINUED CYCLONIC FLOW ACROSS THE REGION. EVENTUALLY SHORTWAVE ENERGY TRANSLATING DOWNSTREAM WILL INCREASE POPS ACROSS SOUTHEASTERN AK. HOWEVER...MOST SOLUTIONS FAVOR THE STRONGER FORCING FARTHER SOUTH INTO BRITISH COLUMBIA WHICH SUGGESTS A BETTER RAINFALL THREAT DOWN THERE. RUBIN-OSTER