Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 630 PM EDT Mon Apr 05 2021 Valid 12Z Fri Apr 09 2021 - 12Z Tue Apr 13 2021 ...A cold pattern for Alaska with deep maritime storms... ...Guidance/Uncertainty Assessment... Guidance shows an amplified large scale pattern this week aloft, with a cold trough dug through Alaska from the high Arctic and a ridge over the Bering Sea/Aleutians Day 4/Friday. The ridge is expected to gradually be worked eastward into the mainland this weekend by ample but still uncertain upper trough energies that feed back into the Bering Sea. Model solutions are well clustered Friday and seem quite reasonable. Differences become increasingly significant days 5-8 (Saturday-next Tuesday), but recent runs of the ECMWF/Canadian remain better aligned with ensembles than the GFS. This is mainly evident with system and flow transition and progression from the Bering Sea/Aleutians to the mainland and Gulf of Alaska. Accordingly, the WPC Alaskan product suite was primarily derived from a blend of the 12 UTC GFS/ECMWF/UKMET/Canadian Day 4 and the 12 UTC ECMWF/Canadian and the GEFS/ECMWF ensemble means Days 5-8 amid growing forecast spread. ...Weather/Hazards Highlights... High Arctic troughing digging over Alaska this week will spread and maintain significant cooling over much of the state into early next week. Digging and phasing energies will support deep cyclogenesis over the northern Gulf of Alaska later this week. This will favor adverse maritime conditions, strong backside winds through southern Alaska, and periods of terrain enhancing precipitation (mainly snow) for Southeast Alaska and the Panhandle. The mainland should dry out this week as frigid high pressure settles in. This will allow below normal temperatures to expand across much of Alaska, with the coldest anomalies (as much as 20-30+ below normal) across the Interior. Systems entering the Bering Sea later week and the weekend are less certain, but will bring quite unsettled maritime conditions. Enhanced winds and precipitation will also progress across the Aleutians and are expected to work in earnest into the mainland next weekend and emerge into the Gulf of Alaska next week along with additional storm energies up from the north Pacific. Schichtel Hazards: - Heavy snow across portions of the Alaska Panhandle, Thu, Apr 8. - High winds across portions of mainland Alaska, Thu-Fri, Apr 8-9. - Much below normal temperatures for parts of the Alaskan Panhandle and mainland Alaska, Thu-Sun, Apr 8-11. 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