Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 650 PM EST Sun Nov 13 2022 Valid 12Z Thu Nov 17 2022 - 12Z Mon Nov 21 2022 ...Overview... Much 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. These features look to peak in strength around when the medium range period begins Thursday, but should stick around through early next week as they gradually weaken. This pattern should direct low pressure systems to the west of the mainland across the Aleutians and the Bering Sea as well as across the northeastern Pacific, leading to potential for precipitation and gusty winds in the Aleutians/Alaska Peninsula and western mainland, with some increasing precipitation chances reaching the southern coast of the mainland and the Panhandle by next weekend. The upper ridge could also cause record-breaking "warm" temperatures across the North Slope as some areas approach or exceed the freezing mark. ...Guidance/Predictability Assessment and Preferences... Model guidance remains agreeable with the overall pattern of a strong upper ridge (3-4 standard deviations above normal for 500mb heights as indicated by the GEFS mean) and a surface high across the Panhandle and mainland that should both slowly weaken through the period. This good agreement for the overall pattern yields fair agreement in the general storm track areas around the ridge as well, with less certainty on the exact surface low tracks. Even on day 4/Thursday there are some placement differences with lows in the Bering Sea that could affect amounts of precipitation and gusty winds (from west-east spread) and the timing (from north-south spread) that make their way into the western mainland. Generally it appears that models have trended toward more onshore precipitation, with the 12Z ECMWF perhaps an outlier in keeping a surface low slower and southward of other guidance and limiting QPF onshore. Thus there also remains some model spread with if and when the ridge could get suppressed on the northern side by Arctic energy rounding it. The GFS runs show better agreement today with maintaining the ridge initially, but more aggressively flatten it compared to the ECMWF later in the week since the latter's surface low and shortwave energy remain over the Bering Sea. 12Z models continue to show reasonably good consensus today with a storm system in the northern Pacific, at least for the latter part of the week as it tracks east and perhaps a bit northward toward the Aleutians. By early next week, more considerable spread arises with its track, with a range of crossing the Aleutians and moving into the Bering Sea or shifting east through the Pacific. There is also better agreement for the existence of another upper/surface low in the northeastern Pacific, but with considerable differences as to its placement as it may gradually shift northeastward toward the Panhandle through the weekend and into early next week. Thus the WPC forecast utilized a blend of the 12Z deterministic model runs to start the period, with gradual increasing of the weighting of ensemble mean components to around half by day 8 given the increasing model spread. ...Sensible Weather and Potential Hazards... Some enhanced precipitation amounts are possible across the Alaska Peninsula lingering into Thursday given moist Pacific southerly inflow. Farther north, the western mainland as well as St. Lawrence Island are becoming more likely to see some light to moderate precipitation and moderate to high winds Thursday-Friday depending on the exact track of the surface low pressure systems, with potentially hazardous onshore flow. Light precipitation could overspread other parts of the mainland as well, but with less confidence. The Aleutians into the Alaska Peninsula can expect rounds of precipitation through much of the 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 into the low 30s Fahrenheit into Thursday-Friday despite polar night approaching, which could be record setting. The rest of the mainland is also likely to be above normal through late week and lasting into early next 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