ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 131 PM EST FRI FEB 20 2015 VALID 12Z TUE FEB 24 2015 - 12Z SAT FEB 28 2015 HIGH AMPLITUDE FLOW OVER THE MID-UPPER LATITUDES NEAR ALASKA TRANSITIONS SOME NEXT WEEK. FORECAST UNCERTAINTY INCREASES THROUGH MIDWEEK AS AMPLE BERING SEA SYSTEM ENERGY ALONG WITH HEIGHT FALLS AND SOME COOLING/PCPN WORKS INCREASINGLY ENEWD THROUGH AN AMBIENT DOWNSTREAM RIDGE BUILT UP THROUGH THE INTERIOR. HAVE BEEN RELUCTANT TO BREAK INTO THE RIDGE TOO STRONGLY...AND THAT NOW BETTER FITS LATEST GUIDANCE TRENDS. UNDERNEATH...LEAD BUT LESS CERTAIN NERN PACIFIC LOW SPECIFICS TUE-THU ARE SLATED TO LIFT NEWD TO THE GULF OF ALASKA AND LEAD TO MODEST DOWNSTREAM INFLOW/PCPN TO SRN/SERN AK. AN ALASKAN RIDGE REBUILDS STRONGLY LATER NEXT WEEK UP THROUGH MUCH OF THE STATE IN RESPONSE TO AMPLIFIED UPSTREAM TROUGH ENERGY APPROACH TO THE BERING SEA. THE 12 UTC GFS AND 00 UTC ECMWF DETERMINISTIC RUNS ARE NOW IN BETTER AGREEMENT INTO TUE/WED AND AS SUCH HAVE BEEN HEAVILY INCLUDED IN THE WPC SOLUTION MIX TO ADD DETAIL AS PER WFO ANCHORAGE COORDINATION. DID ALSO INCLUDE MEAGER INPUTS FROM THE 06 UTC GFS MEAN AND ECMWF/NAEFS ENSEMBLE MEANS FOR CONTINUITY. PREFER A MORE RUN TO RUN CONSISTENT ENSEMBLE MEANS BLENDED FORECAST APPROACH AT LONGER TIME SCALES THAT PLACES EMPHASIS ON THE MORE PREDICTABILE MEDIUM TO LARGER SCALE FORECAST COMPONENTS. THIS ALSO MAINTAINS GOOD WPC CONTINUITY. SCHICHTEL