Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 250 PM EDT Wed Jun 27 2018 Valid 12Z Sun Jul 01 2018 - 12Z Thu Jul 05 2018 An upper low and associated trough is forecast to drift east northeast across northeastern Russia and then into the Chukchi Sea/Arctic Ocean through the weekend and early next week. The models and ensembles still differ on timing/amplitude of the upper tough. The 00z ECMWF was faster than other forecasts. The 12z GFS made a major change to develops a closed low Tue 03 July and continue this low as it moves to the north coast Wed/Thu July 4/5. Given how few models/members have this forecasts, less weighting was given to the 12z GFS and it was even dropped next Wed/Thu July 4/5. More weighting was given tot he ensemble means given the low confidence in the 00z ECMWF/12z GFS. An upper low drifts southeast from just offshore the southeast coast and across Graham/Moresby Islands near 00z Mon. The models/ensembles are coming into better agreement, except the 12z gfs leaves behind a residual trough in the northern Pacific longer than other models and the 06z GEFS Mean. This led to the least weighting given to the GFS forecasts. Manual progs blended the 06z GFS and 00z ECMWF ensemble mean/06z GEFS ensemble mean. In the wake of the departure of the upper trough, heights slowly build west to east across the lower to mid Aleutians, with the positively tilted ridge extending northeast across interior Alaska, and then further east into the Yukon. The above normal heights and temperatures favor a pattern of above normal temperatures in the early to middle portions of next week across southern Alaska, including in the Aleutians. A closed low moves north from the north Pacific across the lower Aleutians into the western Bering Sea in the middle of next week. Minor timing and intensity differences led to a consensus based approach to resolve the differences. Petersen WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can be found at: http://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif www.wpc.ncep.noaa.gov/alaska/akmedr.shtml http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html