Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 650 PM EST Sat Dec 17 2022 Valid 12Z Wed Dec 21 2022 - 12Z Sun Dec 25 2022 ...Cold temperatures continue across the Panhandle through Wednesday-Thursday and across the eastern Interior through late week... ...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 next week, with the largest/most persistent below normal anomalies across the eastern mainland into the Panhandle. 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 through Wednesday with a general pivot to more precipitation for the Alaska Peninsula to Southcentral Alaska and into 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. At the start of the period Wednesday, energy is expected to dig westward across the Alaska mainland, while energy also spills southeast from a western Bering Sea low to possibly form a closed upper low near the Aleutians around Wednesday-Thursday. More uncertainty arises as these features interact, with the eastern energy most likely getting strung out to the north of the western upper low, creating some model differences along the periphery of the Chukchi Sea high dependent on how much this energy can erode the southern side. By late next week there become additional broad scale uncertainties as models like the ECMWF/CMC create a consolidated closed upper low near the southwestern mainland as additional energy tracks southwestward across the state, while GFS runs do not show this consolidation. All these shortwaves and interaction differences end up causing surface low placement to vary considerably from model to model. Ensemble means are somewhat agreeable but particularly in terms of surface low placement, they may be consolidating lows that could actually end up being separate features, as deterministic models do indicate multiple lows. Thus the WPC forecast utilized a mainly deterministic model blend for day 4 but with a gradual ramp-up of the ensemble mean guidance as the period progresses 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 over the northern mainland and 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 into Wednesday, where gusty winds may also be a threat. Then moisture is expected to shift into the Alaska Peninsula to Southcentral Alaska with generally light to moderate precipitation amounts around Thursday, while the Panhandle is also likely to see moist return flow for more widespread precipitation for the latter part of the week. For both areas, there remain uncertainties in the timing and placement details given the surface lows diverging in model guidance. Tate 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