Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 559 PM EDT Sun Jul 19 2020 Valid 12Z Thu Jul 23 2020 - 12Z Mon Jul 27 2020 The forecast for the latter portion of this week through next weekend is for persistent negative mid-level height anomalies across mainland Alaska associated with an arctic upper low and trough situated north of the state. This trough and sfc frontal systems lead to cooler than normal temperatures and a few showery periods, currently centered on Thu and Sat. The ECMWF Ensemble Mean shows a west drift of the trough axis with time, which next weekend opens up the possibility of heights rising and temperatures moderating back towards 30 year normals over the AK panhandle. The primary storm system in the medium range is expected to form over the western Bering Sea and is expected to drift slowly towards the east in the mid to latter portions of this week. The models show typical run to run differences and model to model differences. Without unanimity and general clustering of solutions, a blend of the 12z ECMWF/00z ECMWF/00z ECMWF Ensemble Mean, 12z GFS, and 12z UKMET was used. The 12z Canadian global was more progressive with the system and also for heights to lower in the Gulf of AK/Kodiak/AK peninsula days 6-7, so the Canadian was not included in the blend given the majority of solutions are high amplitude and slow. The ECMWF/UKMET/Canadian cluster better with the 00z ECMWF Ensemble Mean with low pressure in the Arctic Ocean, so the 12z GFS was given less weight there. Finally, on days 6-8, more models produce a couple of waves of low pressure south of the Aleutians and move the lows across the Gulf of AK. A blend of the 06-12z GFS and 00-12z ECMWF was used to mitigate timing differences. Shower coverage and intensity should increase next Sunday and Monday July 27 in the AK panhandle if these solutions are correct. Petersen Additional 3-7 Day Hazard information can be found on the WPC medium range hazards 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