Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 240 PM EST Sun Jan 13 2019 Valid 12Z Thu Jan 17 2019 - 12Z Mon Jan 21 2019 The best clustering of guidance maintains similar ideas from recent days but the full model/ensemble spread continues to suggest uncertainty with various details. An upper high should meander near the northern coast of Mainland Alaska but with a variety of possibilities for day-to-day position and evolution of energy to the south of the upper high. Meanwhile for late this week guidance is still suggesting some degree of interaction among separate opposite-moving features over the Bering Sea/North Pacific, perhaps combining near the eastern Aleutians/southwestern Alaska Peninsula--along with a corresponding low pressure system that subsequently weakens. This system would provide a period of enhanced moisture flow into the Alaska Peninsula/Kenai Peninsula. It is still likely that broad upper troughing will overspread the western and eventually central Pacific with multiple lows/frontal systems possible. The advancing height falls will dislodge initial Bering Sea/northern-eastern Pacific energy, some of which may bring a storm system into the northeastern Pacific next weekend. As the pattern evolves very late in the period there may be a tendency for moisture to reach a broader area along the southern coast and Panhandle. For specifics of the forecast, preferences led to blending aspects of the 00Z ECMWF/CMC and 12Z GFS/06Z FV3 GFS along with a small component of the 06Z GEFS/00Z ECMWF means for days 4-5 Thu-Fri followed by a nearly even model/mean days 6-7 Sat-Sun and more ensemble means day 8 Mon. Operational model emphasis went more to the ECMWF/CMC after Fri while the ECMWF mean provided the greater weight among the two means. The ECMWF/CMC and their means have generally been more consistent with the path/evolution of the upper high near the northern coast of the mainland. GFS runs have varied considerably, with some recent runs becoming quite progressive with Arctic flow to push the high well eastward. The 12Z GFS still eventually strays from the preferred cluster but at least has trended toward holding onto higher heights over the Arctic versus the 00Z/06Z runs. The multi-model blend provides a favorably conservative approach to depicting uncertain details of energy to the immediate south of the upper high. Ensemble means are starting to show evidence of the late week system which a number of operational models over the past couple days have been expecting near the southwest Alaska Peninsula. There is still a fair degree of spread for exact location, leading to preference for an intermediate position which is ultimately somewhat northward of continuity. Farther southeast/east there is decent consensus and continuity for a strong system tracking into the northeastern Pacific next weekend. Into day 7 Sun prefer a compromise between competing model/mean ideas--the former keeping a defined system with a track close to the Panhandle (or Haida Gwaii in the case of the 12Z GFS) versus the latter which appear questionably weak and/or westward. Thus far the ensemble means have provided the most consistent starting point for what may be a series of low pressure/frontal systems pushing across the western/central Pacific. Over the past day ensemble members have trimmed away a bit from the northern side of the envelope for any surface lows, adding a little confidence to the idea that lows/fronts should tend to remain south of the Aleutians during most of the period. Rausch 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