Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 653 PM EST Fri Dec 16 2022 Valid 12Z Tue Dec 20 2022 - 12Z Sat Dec 24 2022 ...Interior to Panhandle cold wave to threaten record temperatures... ...Overview... An upper-level high well to the northwest of the mainland and surface highs north and east of the state will direct bitterly cold air into Alaska, with the largest/most persistent below normal anomalies across the eastern mainland into the Panhandle next week. The general storm track will be south of the highs as vorticity pinches off near the southern mainland around midweek while an upper low may develop near the Aleutians as well. This could lead to some enhanced precipitation/winds over the Aleutians around Tuesday-Wednesday with a general pivot to more precipitation for Southcentral Alaska to the Panhandle for the latter part of next week, but with the details dependent on surface low and shortwave placement. ...Guidance/Predictability Assessment and Preferences... The overall pattern of a Chukchi Sea closed upper high with the main flow to the south is generally locked in in the model guidance. The narrow ridge extending to the south of that high across the western mainland to Alaska Peninsula at the start of the period Tuesday looks to erode as energies come in from both west and east. More specifically, models generally show energy spilling southeast from a western Bering Sea low to possibly form a closed upper low near the Aleutians around Thursday, with fairly good placement agreement in the 12Z GFS and ECMWF but both a bit north of the ensemble mean consensus. Meanwhile around Wednesday-Thursday energy could dig westward across the Alaska mainland and get strung out and possibly eventually interact with the Aleutians low. These details are considerably more nebulous and lead to notable surface low placement differences in the northeast Pacific, with spread quickly increasing between 12Z Wednesday to 12Z Thursday. Thus the WPC forecast utilized a mainly deterministic model blend for days 4-5 and then ramped up the reliance on the more compatible GEFS and EC ensemble means to about half by days 7-8 given the increasing spread and thus decreasing confidence in the details. ...Weather/Hazards Highlights... Very cold air funneling into the state in response to 1050+ mb surface high pressure in far northwestern Canada and deep northerly flow from the Arctic will cause continued colder than average temperatures especially for the southern two-thirds of the mainland into the Panhandle. Minimum temperatures are expected to fall into the -40 to -50 F range in the colder spots of the eastern/southeastern Interior and colder than -10 F on the interior side of the Panhandle. A handful of record cold temperatures are possible especially for low maxima. By the latter part of next week the Panhandle should trend closer to normal in terms of temperatures but the eastern mainland will likely stay quite cold. Meanwhile with confidence growing for upper-level energy to come near the Aleutians along with a possible surface front focusing moisture ahead of it, forecast precipitation amounts have trended up across the Aleutians for Tuesday-Wednesday, where gusty winds may also be a threat. There may also be sufficient moisture for light coastal precipitation from the Alaska Peninsula to Southcentral Alaska and the Panhandle. These precipitation chances rise for the latter part of next week, but with uncertainties in timing and placement details given the surface lows diverging in model guidance. The surface lows could also cause some gusty winds. Tate Hazards: - Much below normal temperatures across portions of mainland Alaska, Mon-Fri, Dec 19-Dec 23. - Much below normal temperatures across portions of the Alaska Panhandle, Mon-Thu, Dec 19-Dec 22. 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