Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 706 PM EDT Tue Jun 20 2023 Valid 12Z Sat Jun 24 2023 - 12Z Wed Jun 28 2023 ...Pattern Overview and Weather/Hazards Highlights... The dominant feature for the weekend into early next week will be a nearly stationary closed upper low and associated surface low over the southern Bering Sea, with multiple shortwave perturbations pivoting around the base of it. The first wave of low pressure is progged to arrive early Sunday and bring moderate to locally heavy rainfall for the coastal mountains from the western Alaska Peninsula to the Kenai Peninsula and southern mainland coast, with 2-4 inches of rainfall possible for the upslope terrain. Gale force winds are also possible across the northern Gulf waters and this could result in potentially hazardous maritime conditions for the upcoming weekend. Portions of the Interior will also have isolated to scattered showers and perhaps a few thunderstorms on most days, but overall QPF should be light in most cases. In terms of temperatures, high temperatures are expected to rise well into the 70s and even near 80 degrees for many of the Interior valleys, and 50s/60s for the central and coastal areas. The Arctic Coast will likely remain cooler with highs generally in the 40s/low 50s most days. ...Guidance Evaluation/Preferences... The 12Z model guidance suite has good overall synoptic scale agreement for the upcoming weekend, and a multi-deterministic model blend suffices as a good starting point in the forecast process. The shortwave disturbance pivoting northeast towards the northern Gulf on Sunday has a stronger signal in the GFS, but similar in timing to the ECMWF, whereas the CMC has a more western track. The next disturbance pivoting around the upper gyre is generally weaker in the guidance and major placement differences exist at this time by next Tuesday, so additional changes in the forecast are expected over the next few days. All of the guidance agrees that the main upper low will remain nearly anchored in place across the southern Bering Sea through the entire forecast period. The ensemble means accounted for about 50-60% of the forecast blend by Tuesday and Wednesday. 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