Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 654 PM EDT Fri Apr 02 2021 Valid 12Z Tue Apr 06 2021 - 12Z Sat Apr 10 2021 ...A cold pattern for Alaska... ...Guidance/Uncertainty Assessment... Guidance over the Alaska region for the extended range period is mostly in agreement with the large scale/synoptic pattern overall, though continue to show more significant embedded system differences later in the period. A deterministic model blend between the reasonably well clustered 12 UTC GFS/ECMWF/UKMET and the 19 UTC National Blend of Models seems to serve well as a forecast starting point days 4-6 (Tue-Thu) and this solution has good ensemble support. After that, some differences in timing of ridging across the Bering and the next systems upstream led to more weighting of the more compatible GEFS/ECMWF ensemble means days 7/8. Manual adjustments were then applied to the blend to ensure offshore low system strength and circulation would be consistent with favorable upper support and to account for weakening due to the blending process. ...Weather/Hazards Highlights... An amplified and cold Arctic vortex is slated to dig over an unsettled North Slope and Interior early next week and significantly cool the region. The lead pattern underneath for early next week will feature lows/frontal systems tracking across the southern Bering Sea and effect the Aleutians/Southwest AK/AKpen before reforming over the northern to eastern Gulf of Alaska. These systems will focus moderately unsettled weather across the region in progressive flow. However, the flow will amplify significantly upstream next week. Amplification will drive Arctic energies and cold air sharply down across the state and the Gulf of Alaska. Stream phasing and low pressure reinforcement across the northern and eastern Gulf should favor periods of terrain enhancing precipitation for much of the period for Southeast Alaska and the Panhandle. The mainland should dry out as frigid high pressure settles in. This would allow below normal temperatures to expand across almost all of Alaska, with the coldest anomalies (as much as 20-30+ below normal) across the Interior. Upstream surface system and progression entering the Bering Sea by later in the week is quite uncertain, but may leading precipitation into the Aleutians and present maritime issues. Schichtel Hazards: - Much below normal temperatures across portions of mainland Alaska, Tue-Thu, Apr 6-Apr 9. 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