Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 601 PM EST Tue Dec 08 2020 Valid 12Z Sat Dec 12 2020 - 12Z Wed Dec 16 2020 ...Guidance and Uncertainty Assessment... Upper flow will be complicated by a retrograding upper low across the Interior, beneath a rather stable upper high over Wrangel Island. This supports a strong surface high pressure over the Beaufort Sea/Arctic Ocean and a storm track along the Aleutians and into the Gulf. The models and ensembles were in decent agreement at best which was not unexpected in a rather complicated pattern evolution. The ensembles were mostly aligned but differed on timing and somewhat the track of the systems in the flow. Overall preferred the ECMWF and its ensembles especially later in the period, but otherwise the 12Z GFS/UKMET/Canadian offered reasonable clustering for the Sat-Mon period. For the weekend, split in the guidance on whether or not to take low pressure across the Peninsula into Bristol Bay (GFS/UKMET) or have it linger just to the east (ECMWF and continuity). Opted to forge a middle ground on top of the island chain with no clear trend or preference. Thereafter, still expect a system to wrap up into the Gulf Sunday as it sheds its fronts to the east. By then, upper low will rotate southwestward as another Pacific shortwave rounds the bend underneath it, allowing it to deepen and lift into the Gulf. The GFS never allows the Pacific energy to organize and shears out the system but the ECMWF and many ensemble members still show a deeper solution, taking it into the southern Gulf next Tue and weakening next Wed. With good ensemble support, preferred this scenario though tempered by a majority ensemble weighting. With the upper high remaining to the north, flow next week could open up from the west between 50-60N, realized by the next system near the western Aleutians. ...Weather/Hazards Highlights... Strong high pressure to the north and storminess in the Gulf will lead to windy conditions over the Interior early next week, though rather dry. Systems in the Gulf or nearby areas will focus precipitation over coastal areas of the AKPen and Kenai peninsula on southeasterly flow as well as the western side of Cook Inlet. Parts of the Panhandle may see at least modest precipitation, though the proximity of the systems to the land areas remains in question. As a result, models solutions vary on intensity there. Temperatures will be near to above normal over northern areas of the mainland, but near to below normal over southwestern areas (under the cold upper low) and much of the Panhandle with offshore flow at the surface. Fracasso Hazards: - High winds across portions of interior Alaska, Sun-Tue, Dec 13-Dec 15. 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