Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 609 PM EDT Sat Jul 16 2022 Valid 12Z Wed Jul 20 2022 - 12Z Sun Jul 24 2022 ...General Overview... A persistent and anomalously deep upper level low will be in place near the Bering Straits and the western Alaska mainland through the end of next week, and then likely meander over southern Alaska while breaking down some. This will equate to widespread cool temperatures by July standards and an increase in showers and a few thunderstorms. Multiple impulses are expected to track around the southern periphery of the main low, and this will increase the prospects for rain and even mountain snow from the Kenai Peninsula to the southeast Panhandle region. ...Guidance/Predictability Assessment... The 12Z model guidance suite strongly supports a highly anomalous upper low over the general vicinity of the Bering Straits by Wednesday, albeit with some trough orientation differences that increase going through the end of the week. The GFS suggests some splitting of the main upper low with the stronger core remaining over the Bering by Friday, whereas the ECMWF is even more anomalous with the core of the low reaching as far south as the Alaska Peninsula. The CMC and UKMET are closer to the ensemble means at this time across the Interior, with the UKMET closer to the consensus compared to earlier runs that were farther east. By the end of the forecast period next Sunday, the GFS portrays a strong low near the Aleutians that is not supported by the ensemble means nor the CMC/ECMWF, and thus a low probability solution. Taking these factors into account, the WPC forecast is initially derived from mainly a CMC/UKMET blend with some of the ECMWF and GFS, and then transitioning to more of the ensemble means whilst still incorporating some of the CMC and ECMWF. ...Sensible Weather... Multiple rounds of scattered showers are likely across the state through the end of the week, with multiple impulses aloft helping to generate lift with steep lapse rates in place. Although there is some uncertainty in the mesoscale aspects, current forecasts indicate the greatest prospects for heavier rain across the southern coastal areas, and especially the windward terrain of the Chugach Mountains where moisture and lift will likely be maximized. Precipitation may be in the form of snow in northwestern and north-central Alaska for the higher elevations, and also the St. Elias Mountains. In terms of temperatures, the main headline will be the persistence of high temperatures running 10-20 degrees below July averages owing to the upper low and also increased cloud cover. Low temperatures are also forecast to cool to below average levels, although the anomalies will be less compared to the afternoon highs. Hamrick 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