Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 358 PM EST Tue Nov 06 2018 Valid 12Z Sat Nov 10 2018 - 12Z Wed Nov 14 2018 The Alaska medium range period (Sat-Wed) features a main upper level low/elongated trough initially over the Bering Sea and Aleutians which drops southward on Day 5 and then lingers/drifts slowly eastward over the Alaska Peninsula or western Gulf. At the surface, this translates to initially two distinct low pressure areas -- one over the Bering Sea, and another one lifting northward into the Gulf. Models are beginning to show greater probability that these two eventually evolve into one surface low which lingers near or just south of the Alaska Peninsula days 6-7, and then beginning to drift slowly eastward by day 8. Meanwhile, downstream eastern Pacific ridging builds into western Canada and likely to some degree over Mainland Alaska as well. In the beginning of the period there is fairly good clustering between the latest runs of the GFS/ECMWF/UKMET though the ECMWF remains farthest west with the main upper low/trough. The 12z GFS trended slightly westward towards the ECMWF though so opted to use equal weighting of these two models which results in a middle-ground solution close to the ensemble means. After this time, spread increases and confidence decreases on strength/placement of individual small-scale details embedded within the larger-scale flow. The blend for todays Alaska forecast used majority deterministic guidance days 4-5, with increasing weighting of the ensemble means by days 6-7 to help mitigate/smooth out the noise and smaller scale differences. This blend resulted in a solution very close to yesterdays WPC continuity. This pattern should bring a signficant increase in moisture and precipitation into the Gulf of Alaska and southern coastal and Panhandle regions ahead of the deepening surface low in the Gulf. There is a multi-model signal for signficant rainfall from roughly the western southern coast to the northern Panhandle region with determinisitic solutions showing 2-3+ 24-hour amounts around Saturday to Monday time-frame. In addition, strong winds in association with the surface low will be possible most likely along the coast. Santorelli 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 http://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html