Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 628 PM EST Sun Nov 14 2021 Valid 12Z Thu Nov 18 2021 - 12Z Mon Nov 22 2021 ...Much below normal temperatures likely across Alaska through the medium range period... ...Overview and Guidance Evaluation/Preferences... An expansive and blocky upper ridge over Russia should keep the Alaska region storm track along/south of the Aleutians and into the Gulf during the extended range. A deep upper low centered over the Gulf on Thursday will weaken as it retreats into Canada by Friday, although general troughing should linger across central and southern Alaska through the weekend. To the West, another deep low will translate south of the Aleutians and into the Gulf by early next week. The 12z GFS, ECMWF, and CMC show reasonable agreement with the large scale pattern for a purely deterministic model blend days 4-5/Thursday-Friday. After this, the typical detail uncertainties begin to arise, particularly regarding a few reinforcing shortwaves rounding the base of the Aleutians low and lifting north from the north Pacific. To help mitigate these harder to resolve details, WPC blended more of the ensemble means for the late period. The GFS and ECMWF however show enough agreement with the ensemble means to maintain at least modest amounts of those models in the blend, which should provide some needed additional definition/depth to individual systems. This approach also maintains good continuity from yesterdays forecast. ...Weather/Hazard Highlights... Precipitation over Alaska should be confined to the Aleutians/Southern Coast/Panhandle, with much of the mainland remaining very cold and dry, other than maybe a few snow showers. Low pressure in the Gulf on Thursday-Friday will continue to bring a period of moderate to locally heavy precipitation to much of the Panhandle region. In addition, favorable flow funneling through the mountain ranges of southern Alaska may result in the potential for localized but strong outflow winds into Thursday across downwind locations of southeast Alaska. A system into the Aleutians late this week should bring unsettled conditions to the region with light to moderate precipitation spreading towards the Peninsula and Southern Coast as well. Enhanced precipitation should again move into the Panhandle by next weekend as the next low pressure system approaches. Much below normal temperatures should prevail across much of Alaska, especially the central and southern regions, through next week as surface high pressure becomes established across the state. The most pronounced anomalies should be over the western to southern part of the state where daytime highs could be as much as 20-30+ degrees below normal. Temperatures should remain below normal into next weekend, but may moderate slightly as the upper trough weakens and upper ridging attempts to sneak in from the west. The exception to this will be the North Slope, where temperatures should remain closer to normal through next weekend, though a brief period of modestly above normal temps are possible Friday and Saturday. Santorelli Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook 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