Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 630 PM EST Sat Nov 12 2022 Valid 12Z Wed Nov 16 2022 - 12Z Sun Nov 20 2022 ...Overview... Most of Alaska will be dominated by a ridgy pattern in both the upper levels and at the surface as a strong high extends into the mainland from midweek into next weekend. This should direct a couple of low pressure systems to the west of the mainland, with an initial one reaching the Arctic Wednesday and another crossing the Aleutians around early Wednesday and continuing northward across the Bering Sea. These lows may cause gusty winds and some precipitation over the Aleutians and into northwestern portions of the mainland. By late in the week, the ridge pattern generally holds on but some shortwaves and surface lows could provide some rounds of precipitation to the Aleutians and Alaska Peninsula, with the storm track to the south of the ridge. ...Guidance/Predictability Assessment and Preferences... While model guidance is agreeable with the overall pattern of an upper ridge and surface high across the Panhandle and mainland, models already start to exhibit some differences at the beginning of the period with the low tracks across the Aleutians into the Bering Sea. GFS runs quickly track a strong surface low (which seems to arise from phasing of what is currently Tropical Storm Yamaneko in the West Pacific with an extratropical system) from the Aleutians northward across the Bering Sea Wednesday-Friday, while ECMWF runs have been persistently slower with the low once it reaches the Bering. The 12Z UKMET clustered well with the ECMWF while the CMC is somewhat closer to the GFS. While these model differences are minor to moderate for a medium range Alaska forecast, any west-east spread could cause impactful differences in gusty winds and precipitation across the Aleutians and western mainland, while north-south spread will particularly affect the timing of any impacts. Then GFS runs take their stronger low eastward across the Arctic and at upper levels tend to suppress/flatten the northern side of the ridge. At this time, prefer a middle ground solution but favoring the GFS somewhat less given the strength of the ridge--it would likely be difficult to suppress. The ensemble means keep a stronger ridge through late week, less like the GFS and more like the ECMWF. Models appear more agreeable today with one surface low position south of the western Aleutians on Friday, but with less certainty in its track after that into the weekend. There is also more uncertainty farther east with another Pacific low that may trend northeastward toward the Panhandle with time. Thus the WPC forecast utilized a blend of mostly deterministic model runs but also a bit of EC and GEFS ensemble means to start the period, with gradual increasing of the weighting of ensemble mean components to a little over half by day 8. ...Sensible Weather and Potential Hazards... Some enhanced precipitation amounts are possible across the Alaska Peninsula around Wednesday-Thursday with moist Pacific inflow ahead of a possible cold front. Farther north, the western mainland as well as St. Lawrence Island could see some light to moderate precipitation and moderate to high winds Wednesday-Thursday depending on the exact track of the surface low pressure systems, with potentially hazardous onshore flow. The Aleutians can expect rounds of precipitation through much of next week into next weekend, but uncertainty remains with the details of amounts and timing. Some precipitation may also reach Southcentral Alaska and perhaps the Panhandle by next weekend depending on where surface lows set up. The overall upper ridge pattern will lead to above average temperatures across much of the state for the period. The North Slope looks to see the highest anomalies above normal, with portions even reaching slightly above freezing. Temperatures in Utqiagvik could reach 30F around Wednesday-Thursday despite polar night approaching. The rest of the mainland is also likely to be above normal through late week, with more of a mix of above/below average temperatures for the Panhandle. 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