Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 616 PM EDT Thu Mar 18 2021 Valid 12Z Mon Mar 22 2021 - 12Z Fri Mar 26 2021 ...Guidance/Uncertainty Assessment... Models and ensembles overall offer better than average agreement for the pattern evolution and significant features for much of the next week. The Day 4-8 (Monday-Wednesday) forecast was primarily derived from a composite blend of well clustered guidance from the 12 UTC ECMWF/Canadian and ECMWF ensemble mean. The 12 UTC GFS/GEFS do not match continuity as well and the soon to be operational experimental GFS trended toward the favored composite. Forecast spread increases by days 7/8 when a composite of the 12 UTC GEFS/ECMWF ensemble means was mainly used along with the best clustered guidance from the 12 UTC ECMWF to add a bit more system detail. Composites mitigate less predictable smaller scale differences. WPC continuity is reasonably well maintained with this forecast methodology in a pattern with above normal predictability. ...Weather/Hazards Highlights... The Aleutians/AKPen should see a period of precipitation and enhanced winds early next week on the northwest side of a northeastward lifting North Pacific system. This maritime threat storm will then quickly bring increasing moisture to the southern coast and especially the Panhandle Tuesday-Wednesday where there is the highest potential for terrain enhancing heavy precipitation given the lower-latitude origin of the moisture. Bering Sea upper troughing, surface system development and onshore track may spread some organized snows into the Interior/Southwest AK early next week, but stream interactions and continuity with the features has been less than stellar. Subsequent system energies slated to track across the Bering Sea would bring a front across the southern Bering and Aleutians into midweek and again later next week. These are expected to be accompanied by precipitation and some brisk winds. Moderate activity is slated with some uncertainty to progress into the western mainland and the Gulf of Alaska mid-later week with both a lead and secondary systems. Schichtel Hazards: - No significant hazards are expected over Alaska during this forecast period. Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can also be found at: https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html